@misc{AdelmannSchramChewetal., author = {Adelmann, Christoph and Schram, Tom and Chew, Soon Aik and Woicik, J. C. and Brizzi, Simone and Tallarida, Massimo and Schmeißer, Dieter and Horiguchi, Naoto and Elshocht, Sven van and Ragnarsson, Lars-{\AA}ke}, title = {On the scalability of doped hafnia thin films}, series = {Applied Physics Letters}, journal = {Applied Physics Letters}, number = {104}, issn = {0003-6951}, doi = {10.1063/1.4870075}, pages = {122906-1 -- 122906-4}, abstract = {The scaling behavior of Gd- and Al-doped HfO2 films as gate dielectrics in metal-oxide-semiconductor (MOS) capacitors was studied. For equivalent oxide thicknesses (EOTs) in the range of 10 {\AA}, crystallized Gd:HfO2 showed higher leakage current densities than crystallized Al:HfO2, with undoped HfO2 in between. Ultimately, the scalability of Al:HfO2 was limited by the ability to crystallize the films at a given thermal budget. As a result, for post-deposition annealing at 800 °C, the EOT of Al:HfO2 based MOS capacitors was limited to ∼8 {\AA}. However, for such an EOT, leakage current densities were reduced by about 100× with respect to HfO2. This demonstrates the high potential of Al:HfO2 for low-standby-power MOS devices.}, language = {en} } @misc{MandalHenkelSchmeisser, author = {Mandal, Dipankar and Henkel, Karsten and Schmeißer, Dieter}, title = {Improved performance of a polymer nanogenerator based on silver nanoparticles doped electrospun P(VDF-HFP) nanofibers}, series = {Physical Chemistry Chemical Physics}, volume = {2014}, journal = {Physical Chemistry Chemical Physics}, number = {16}, issn = {1463-9084}, doi = {10.1039/C3CP55238A}, pages = {10403 -- 10407}, abstract = {We report on the electrospinning of poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] nanofibers doped with silver nanoparticles for the preparation of a polymer based nanogenerator (PNG). It has been found that the yield of the piezoelectric phase is increased by the addition of silver nanoparticles. Furthermore, defects in the P(VDF-HFP) electrospun fibers are removed resulting in a significant enhancement in the output power of the PNG. A maximum generated PNG output voltage of 3 V with a current density of 0.9 μA cm-2 is achieved.}, language = {en} } @misc{SchmeisserHaeberleBarquinhaetal., author = {Schmeißer, Dieter and Haeberle, J{\"o}rg and Barquinha, Pedro and Gaspar, Diana and Pereira, Lu{\´i}s and Martins, Rodrigo and Fortunato, Elvira}, title = {Electronic structure of amorphous ZnO films}, series = {Physica Status Solidi C}, volume = {11}, journal = {Physica Status Solidi C}, number = {9-10}, issn = {1610-1642}, doi = {10.1002/pssc.201400010}, pages = {1476 -- 1480}, abstract = {We use resonant photoemission spectroscopy (resPES) to study the electronic properties of amorphous ZnO (a-ZnO) layers. We report on the core levels, the valence band (VB) PES data, and the X-ray absorption (XAS) data which we use for the conduction band (CB) density of states. From these results we are able to derive the partial density of states (pDOS) of O2p and Zn4s4p states in the VB and CB, respectively as well as a band scheme. At the O1s resonance we observe a band of localized defect states which is located between the Fermi energy and the CBM. At the Zn2p edge the XAS data indicate that localized Zn4s4p states are involved in the DOS starting already at the Fermi energy.}, language = {en} } @misc{TallaridaDasCibrevetal., author = {Tallarida, Massimo and Das, Chittaranjan and Cibrev, Dejan and Kukli, Kaupo and Tamm, Aile and Ritala, Mikko and Lana-Villarreal, Teresa and Gómez, Roberto and Leskel{\"a}, Markku and Schmeißer, Dieter}, title = {Modification of Hematite Electronic Properties with Trimethyl Aluminum to Enhance the Efficiency of Photoelectrodes}, series = {The Journal of Physical Chemistry Letters}, volume = {5}, journal = {The Journal of Physical Chemistry Letters}, number = {20}, doi = {10.1021/jz501751w}, pages = {3582 -- 3587}, abstract = {The electronic properties of hematite were investigated by means of synchrotron radiation photoemission (SR-PES) and X-ray absorption spectroscopy (XAS). Hematite samples were exposed to trimethyl aluminum (TMA) pulses, a widely used Al-precursor for the atomic layer deposition (ALD) of Al2O3. SR-PES and XAS showed that the electronic properties of hematite were modified by the interaction with TMA. In particular, the hybridization of O 2p states with Fe 3d and Fe 4s4p changed upon TMA pulses due to electron inclusion as polarons. The change of hybridization correlates with an enhancement of the photocurrent density due to water oxidation for the hematite electrodes. Such an enhancement has been associated with an improvement in charge carrier transport. Our findings open new perspectives for the understanding and utilization of electrode modifications by very thin ALD films and show that the interactions between metal precursors and substrates seem to be important factors in defining their electronic and photoelectrocatalytic properties.}, language = {en} } @misc{KrammLefevreBogdanoffetal., author = {Kramm, Ulrike Ingrid and Lef{\`e}vre, Michel and Bogdanoff, Peter and Schmeißer, Dieter and Dodelet, Jean-Pol}, title = {Analyzing Structural Changes of Fe-N-C Cathode Catalysts in PEM Fuel Cell by M{\"o}ßbauer Spectroscopy of Complete Membrane-Electrode-Assemblies}, series = {The Journal of Physical Chemistry Letters}, volume = {2014}, journal = {The Journal of Physical Chemistry Letters}, number = {5}, issn = {1948-7185}, doi = {10.1021/jz501955g}, pages = {3750 -- 3756}, abstract = {The applicability of analyzing by M{\"o}ßbauer spectroscopy the structural changes of Fe-N-C catalysts that have been tested at the cathode of membrane electrode assemblies in proton exchange membrane (PEM) fuel cells is demonstrated. The M{\"o}ßbauer characterization of powders of the same catalysts was recently described in our previous publication. A possible change of the iron species upon testing in fuel cell was investigated here by M{\"o}ßbauer spectroscopy, energy-dispersive X-ray cross-sectional imaging, and neutron activation analysis. Our results show that the absorption probability of γ rays by the iron nuclei in Fe-N-C is strongly affected by the presence of Nafion and water content. A detailed investigation of the effect of an oxidizing treatment (1.2 V) of the non-noble cathode in PEM fuel cell indicates that the observed activity decay is mainly attributable to carbon oxidation causing a leaching of active iron sites hosted in the carbon matrix.}, language = {en} } @misc{SzakacsLefevreKrammetal., author = {Szakacs, Csaba E. and Lef{\`e}vre, Michel and Kramm, Ulrike Ingrid and Dodelet, Jean-Pol and Vidal, Fran{\c{c}}ois}, title = {A density functional theory study of catalytic sites for oxygen reduction in Fe/N/C catalysts used in H2/O2 fuel cells}, series = {Physical Chemistry Chemical Physics}, volume = {2014}, journal = {Physical Chemistry Chemical Physics}, number = {16}, issn = {1463-9076}, doi = {10.1039/C3CP55331K}, pages = {13654 -- 13661}, abstract = {The oxygen reduction catalytic activity of carbon-supported FeN4 moieties bridging micropores between two graphene sheets was investigated by density functional theory (DFT). Based on the FeN2+2/C structure proposed earlier by our group, two types of FeN2+2/C structures were considered: one mostly planar and one in which the Fe ion is significantly displaced out of the graphitic plane. A structure in which the FeN4 moiety is embedded in an extended graphene sheet (FeNpyri4/C) was also considered. In addition, we have investigated the influence of an axial pyridine group approaching the Fe centre. The formation energy is lowest for the planar FeN2+2/C structure. The overall downhill behaviour of the relative free energy vs. the reaction step suggests that most structures have catalytic activity near zero potential. This conclusion is further supported by calculations of the binding energies of adsorbed O2 and H2O and of the O-O bond lengths of adsorbed O2 and OOH. The side-on interaction of adsorbed O2 is preferred over the end-on interaction for the three basic structures without the axial pyridine. The pyridine coordination produces a stronger binding of O2 for the planar FeN2+2/C and the FeNpyri4/C structures as well as a dominant end-on interaction of O2. The energy levels of the planar FeN2+2/C structure with and without the pyridine ligand are nearly equal for iron spin states S = 1 and S = 2, suggesting that both configurations are formed with similar concentration during the preparation process, as also previously found for two of the iron sites by M{\"o}ssbauer spectroscopy experiments.}, language = {en} } @misc{IndraMenezesSahraieetal., author = {Indra, Arindam and Menezes, Prashanth W. and Sahraie, Nastaran Ranjbar and Bergmann, Arno and Das, Chittaranjan and Tallarida, Massimo and Schmeißer, Dieter and Strasser, Peter and Driess, Matthias}, title = {Unification of Catalytic Water Oxidation and Oxygen Reduction Reactions: Amorphous Beat Crystalline Cobalt Iron Oxides}, series = {Journal of the American Chemical Society}, volume = {2014}, journal = {Journal of the American Chemical Society}, number = {136}, issn = {1520-5126}, doi = {10.1021/ja509348t}, pages = {17530 -- 17536}, abstract = {Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions.}, language = {en} } @misc{DasHenkelTallaridaetal., author = {Das, Chittaranjan and Henkel, Karsten and Tallarida, Massimo and Schmeißer, Dieter and Gargouri, Hassan and K{\"a}rkk{\"a}nen, Irina and Schneidewind, Jessica and Gruska, Bernd and Arens, Michael}, title = {Thermal and plasma enhanced atomic layer deposition of TiO2: Comparison of spectroscopic and electric properties}, series = {Journal of Vacuum Science and Technology A}, volume = {2015}, journal = {Journal of Vacuum Science and Technology A}, number = {33}, issn = {1520-8559}, doi = {10.1116/1.4903938}, pages = {01A144-1 -- 01A144-8}, abstract = {Titanium oxide (TiO2) deposited by atomic layer deposition (ALD) is used as a protective layer in photocatalytic water splitting system as well as a dielectric in resistive memory switching. The way ALD is performed (thermally or plasma-assisted) may change the growth rate as well as the electronic properties of the deposited films. In the present work, the authors verify the influence of the ALD mode on functional parameters, by comparing the growth rate and electronic properties of TiO2 films deposited by thermal (T-) and plasma-enhanced (PE-) ALD. The authors complete the study with the electrical characterization of selected samples by means of capacitance-voltage and current-voltage measurements. In all samples, the authors found a significant presence of Ti3+ states, with the lowest content in the PE-ALD grown TiO2 films. The observation of Ti3+ states was accompanied by the presence of in-gap states above the valence band maximum. For films thinner than 10 nm, the authors found also a strong leakage current. Also in this case, the PE-ALD films showed the weakest leakage currents, showing a correlation between the presence of Ti3+ states and leakage current density.}, language = {en} } @misc{GarainSinhaAdhikaryetal., author = {Garain, Samiran and Sinha, Tridib Kumar and Adhikary, Prakriti and Henkel, Karsten and Sen, Shrabanee and Ram, Shanker and Sinha, Chittaranjan and Schmeißer, Dieter and Mandal, Dipankar}, title = {Self-Poled Transparent and Flexible UV Light-Emitting Cerium Complex-PVDF Composite: A High-Performance Nanogenerator}, series = {ACS Applied Materials \& Interfaces}, volume = {2015}, journal = {ACS Applied Materials \& Interfaces}, number = {7}, issn = {1944-8244}, doi = {10.1021/am507522r}, pages = {1298 -- 1307}, abstract = {Cerium(III)-,N-dimethylformamide-bisulfate [Ce(DMF)(HSO4)3] complex is doped into poly(vinylidene fluoride) (PVDF) to induce a higher yield (99\%) of the electroactive phases (β- and γ-phases) of PVDF. A remarkable enhancement of the output voltage (∼32 V) of a nano-generator (NG) based on a nonelectrically poled cerium(III) complex containing PVDF composite film is achieved by simple repeated human finger imparting, whereas neat PVDF does not show this kind of behavior. This high electrical output resembles the generation of self-poled electroactiveβ-phase in PVDF due to the electrostatic interactions between the fluoride of PVDF and the surface-active positive charge cloud of the cerium complex via H-bonding and/or bipolar interaction among the opposite poles of cerium complex and PVDF, respectively. The capacitor charging capability of the flexible NG promises its applicability as piezoelectric-based energy harvester. The cerium(III) complex doped PVDF composite film exhibit an intense photoluminescence in the UV region, which might be due to a participation of electron cloud from negative pole of bipolarized PVDF. This fact may open a new area for prospective development of high-performance energy-saving flexible solid-state UV light emitters.}, language = {en} } @inproceedings{KrenekCimrovaSeifarthetal., author = {Krenek, Radim and Cimrova, Vera and Seifarth, Olaf and Bocharova, Vera and Gorodyska, Ganna and Sidorenko, Alexander and Schmeißer, Dieter and Stamm, Manfred}, title = {Electronic Properties of Metals Embedded into Porous Polymeric Nanotemplates}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 108}, abstract = {We report on electrical measurements (current-voltage characteristics (CVC)) of metals which are templated via porous polymeric nanotemplates. The nanotemplates are based on self-organization of poly(styrene-block 4-vinylpyridine) (PS-PVP). The cylindrical pores of 8 nm in the diameter are ordered in a hexagonal lattice (24 nm in the period). Chromium and gold were embedded in the nanotemplates by magnetron sputtering, nickel was electrodeposited. These thin films were characterized by AFM, ellipsometry, x-ray reflectivity, XAS, XPS and NEXAFS. CVC were acquired by a connection common for light emitting diodes discussing a further use of nanotemplated metals in these devices. To make the connection, the nanotemplate was deposited on glass with ITO electrodes, then metal was embedded into it and finally Al electrodes were evaporated on the device. Behaviour of space charge limited currents (SCLC) was observed. Also, we deal with the electrical mode of AFM as well. Finally electronic behaviour of the metallic nanorods embedded in polymeric nanotemplates is discussed in respective to the structure and chemical composition obtained by AFM and x-ray techniques.}, language = {en} } @inproceedings{TallaridaSohalSchmeisser, author = {Tallarida, Massimo and Sohal, Rakesh and Schmeißer, Dieter}, title = {Electronic properties of the 2x1 3C-SiC surface reconstruction studied with resonant photoemission}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, isbn = {0420-0195}, pages = {S. 239}, abstract = {We have studied the 2x1 reconstructed surface of the 3C-SiC polytype by means of photoemission spectroscopy. The reconstruction was characterized through Si2p and C1s core level and angle-integrated valence band spectroscopy, and confirmed by the observation of a two-domain 2x1 LEED pattern. The electronic properties of this surface were investigated by collecting valence band spectra at photon energies near the Si2p and C1s absorption edges. The results show a strong dependence of the photoemission intensity on the excitation energy with characteristic resonances for certain valence band features. With a detailed study of the resonances we are able to assign the electronic origin of the resonating states and the nature of the electronic transition near the absorption edges.}, language = {en} } @inproceedings{WehnerHofmannSchmeisseretal., author = {Wehner, Stefan and Hofmann, Patrick and Schmeißer, Dieter and Brand, Helmut R. and K{\"u}ppers, J{\"u}rgen}, title = {Pattern formation in the CO + O reaction on Ir(111) surfaces under the influence of noise}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 708}, abstract = {The rate of CO oxidation on Ir(111) surfaces exhibits bistability at T = 500 K in a range of the CO fraction Y in the CO + O reactant gas flux. Quadrupol mass spectrometer measurements of the CO2 rates as a function of the noise strength imposed on Y are well reproduced by parameter-free modeling. We present Photoelectron emission microscopy (PEEM) measurements and 2D calculations of the spatio-temporal patterns of CO and O rich domains. The role of combined multiplicative and additive noise on Y for CO and O domain wall motion and island nucleation-growth-coalescence processes is analysed. For small noise amplitudes few islands nucleate and grow up to some 100 µ m in diameter, before they merge with another island. With increasing noise amplitudes more islands nucleate. With large noise amplitudes bursts to and switching between the branches is observed. The domain wall velocity is found to be independent of the noise strength and island size.}, language = {en} } @inproceedings{WehnerHoffmannSchmeisseretal., author = {Wehner, Stefan and Hoffmann, Patrick and Schmeißer, Dieter and Brand, Helmut R. and K{\"u}ppers, J{\"u}rgen}, title = {CO oxidation on Ir(111) surfaces: consequences of anisotropic diffusion and noise}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 475}, abstract = {The CO oxidation reaction on Iridium(111) surfaces shows bistability in a limited range of the CO fraction of the reactant gas flux Y and a wide range of temperatures T. The two branches are characterized by their reactivity for CO2 formation. The upper rate (high CO2 formation) rate is related to high oxygen coverage on the surface, the lower rate (little CO2 formation) to high CO coverage. Quadrupol mass spectroscopy and PEEM (photoelectron emission microscopy) was employed to study the influence of a noisy reactant gas flux composition on the spatio-temporal pattern development in the CO oxidation reaction on flat Ir(111) and stepped Ir(977) surfaces. PEEM shows nucleation and growth of few oxygen resp. CO islands at small noise amplitudes. Anisotropic diffusion of CO parallel and normal to the steps causes elliptic shapes of large islands. The long axes of the ellipses are aligned along the steps. At increased noise amplitudes the density of islands becomes larger. 2D modeling of the phenomena based on reaction-diffusion differential equations reproduces the experimental findings quite nicely.}, language = {en} } @inproceedings{SeimeHenkelPaloumpaetal., author = {Seime, Bernd and Henkel, Karsten and Paloumpa, Ioanna and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Buffer layer investigation of MFIS stacks with an organic ferroelectric layer}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 216}, abstract = {Ferroelectric field effect transistors are considered as future non volatile and non destructive readout memory cells. Conventional Perowskite-type ferroelectric materials are shown to work but they need expensive high temperature and high partial pressure processing steps inducing also unintentional and undefined interfacial layers.A possible low cost solution is the use of poly[vinylidene fluoride trifluoroethylene (P[VDF/TrFE]). This is a ferroelectric polymer which can be spin coated at room temperature onto silicon suited with well defined buffer layers. Using P[VDF/TrFE] we focus on metal ferroelectric insulator semi-conductor (MFIS) structures. In MFIS structure a part of the programming voltage drops over the buffering insulator. We report on attempts to minimize this fraction by optimizing the voltage divider over the buffer and the ferroelectric layers. CV measurements for different thickness of the buffer (10-235nm) and the ferroelectric layer(100nm-1μm) and for different permittivity values of the buffer layer(SiO2, Al2O3, HfO2) will be presented. This work is supported by Deutsche Forschungsgemeinschaft within priority program 1157 (DSCH 745/11-1).}, language = {en} } @inproceedings{MandalMuellerSeifarthetal., author = {Mandal, Dipankar and M{\"u}ller, Klaus and Seifarth, Olaf and Hoffman, Patrick and Henkel, Karsten and Schmeißer, Dieter}, title = {Study of reactions at the interface P(VDF/TrFE)/Al and P(VDF/TrFE)/PEDOT:PSS}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 797}, abstract = {Due to potential use in non volatile memory application, Poly(vinylidene fluoride/trifluoroethylene) (P(VDF-TrFE)) is a great deal of interest, especially to produce organic field effect transistors (OFET). Right now it was found that Aluminum is one of the cost-effective inorganic electrode candidate. On the other hand, poly(3,4 ethylenedioxythiophene):poly(4-styrenesulfonate)(PEDOT:PSS) shows promising behavior for the application as organic electrode. In part of our investigations we have systematically studied surface interactions of organic ferroelectric thin films (P(VDF-TrFE))with inorganic (Al) and organic layers (PEDOT:PSS). By X-ray photoelectron spectroscopy (XPS) is has been found that there is a interfacial reaction with Al and the copolymer. In contrast, for electrodes, made of PEDOT: PSS, we found not such kind of behavior. In this case, we found no evidence for any surface reaction. Furthermore, we present our results concerning the orientation of permanent dipoles in the co-polymer (formed between hydrogen and fluorine atom). Here, we use Near-edge X-ray absorption fine structure (NEXAFS) analysis at the U 49/2 - PGM2 beam line of the BESSY-II Synchrotron. This work is supported by Deutsche Forschungsgemeinschaft (DFG) within priority program 1157 (DSCH 745/11-1).}, language = {en} } @inproceedings{HenkelSohalTorcheetal., author = {Henkel, Karsten and Sohal, Rakesh and Torche, Mohamed and Schwiertz, Carola and Burkov, Yevgen and Schmeißer, Dieter}, title = {PrOx/AlON stacks as a high-k candidate on SiC}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 215}, abstract = {We study the chemical stability and electrical properties of Pr-oxides-SiC MIS stacks. In MISFET devices for high power applications the electric field scaling at the interface between semiconductor and insulator is determined by the ratio of their permittivity values. A high-k material can be used to optimize the performance of such devices. In previous studies we had to understand that the chemical reactivity of the PrOx/SiC interface causes a destructive interaction yielding silicate and graphite formation as well as poor electrical performance after direct deposition of PrOx onto SiC. Therefore we introduced an additional chemically inert layer and in this contribution we focus on PrOx/AlON as a suitable insulator stack. In our spectroscopic investigations we recognized a stable AlON/3C-SiC interface even for annealing steps up to 900∘C. First electrical characterizations are performed on Si substrates and we find a strong improvement in the leakage current by several orders of magnitude down to values of 10-7 A/cm2 at an EOT of 4nm and interface state densities of mean values of 5*1011/eVcm2. We also report on our ongoing electrical characterization of such stacks on SiC substrates. This work is supported by Deutsche Forschungsgemeinschaft within priority program 1157 (DSCH 745/9-2).}, language = {en} } @inproceedings{MuellerSchmeisser, author = {M{\"u}ller, Sebastian and Schmeißer, Dieter}, title = {The initial stages of Chromium growth on Titaniumdioxide-Investigations using synchrotron radiation}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 598}, abstract = {We investigate the interface of Cr-TiO2 during the initial stages of Cr deposition. Experiments are carried out at BESSY II (BL U49/2-PGM2). Using XPS, XAS and ResPES we obtain information about electronic structure at the interface. We confirm the results of growth studies by Christian Winde obtained by TEM-EELS. In addition, we find that Cr deposition induces two gap states which appear about 1 eV and 3 eV below EF. Using ResPES, these states can be identified as being Cr-like and Ti-like respectively. Core-level-XPS and CIS-spectra of the lower gap state indicate the existence of mainly Cr4+ at low coverage (< 1 ML). At higher coverage (≈ 2.5 ML) metallic Cr is observed as well as metallic Ti. Oxidized Cr occurs mainly as Cr3+. CIS-spectra of higher gap state show metallic behavior with both Cr- and Ti-like character. CIS-spectra of lower gap-state confirm the existence of Cr3+. Reference: Christian Winde, Herstellung und Charakterisierung von Cr Schichten auf TiO2 (110)Oberfl{\"a}chen, PhD Thesis, University of Stuttgart, 2002}, language = {en} } @inproceedings{NielsenBauerSennetal., author = {Nielsen, Karl-Wilhelm and Bauer, Sebastian and Senn, Konrad and Goennenwein, Sebastian T. B. and Opel, Matthias and Cezar, Julio C. and Schmeißer, Dieter and Gross, Rudolf}, title = {X-ray magnetic circulardichroism in cobalt-doped ZnO}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 42}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 454}, abstract = {Cobalt-doped ZnO is a diluted magnetic semiconductor with a reported Curie-temperature well above 300 K. Nevertheless, the origin of the ferromagnetic exchange still is under debate. To clearify this issue we have investigated cobalt-doped ZnO thin films with x-ray magnetic circular dichroism (XMCD). The (0001)-oriented Zn0.95Co0.05O thin films were grown on (0001) ZnO, (0001) Al2O3, and (0001) ScAlMgO4 substrates by pulsed laser deposition. The magnetic properties were measured by SQUID magnetometry and XMCD. Room temperature magnetization measurements by SQUID magnetometry and XMCD in the fluorescence yield mode reveal ferromagnetic behavior with similar shape of the magnetization curves, however, with different absolute values. XMCD magnetization in total electron yield, which is surface sensitive, show only small magnetic moments, most likely due to a magnetically dead surface layer. This work is supported by the DFG via SPP1157.}, language = {en} } @inproceedings{KachelRichterPhilipetal., author = {Kachel, Krzysztof and Richter, Matthias and Philip, Shine and Paloumpa, Ioanna and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Performance of organic solar cells with a ferroelectric component}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 153}, abstract = {Charge dissociation and recombination are important factors for the efficiency of organic solar cells, even in blended systems of different polymers. As a new approach, the influence of additional blended ferroelectric nanoparticles on the solar cell performance is investigated. The ferroelectric dipole of the nanoparticle causes a local field, which could lead to a longer recombination time of the polaron pairs. As solar cell system we use bulk heterojunction cells or bilayer structures based on regioregular poly(3-hexylthiophene) (P3HT) as the donor and phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor molecule. As ferroelectric additive we use the ferroelectric copolymer poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) or BaTiO3. The copolymer is spincoated as ultrathin film of 20nm, whereas the BaTiO3 is incorporated as nanodispersion into the donor-acceptor blend. We present the solar cell parameters for the different geometries and ferroelectric materials as a function of ferroelectric content and of the alignment of the ferroelectric dipoles after application of an external electric field.}, language = {en} } @inproceedings{KlocekFriedrichZagorodniyetal., author = {Klocek, Jolanta and Friedrich, Daniel and Zagorodniy, Kostyantyn and Schmeißer, Dieter}, title = {Spectroscopic investigations of interaction between C60 fullerene and nitrogen atom from amine group}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 231}, abstract = {We investigated interactions between fullerene molecule and amine group from 3-aminopropyl-trimethoxysilane (3AT). Theoretical calculations show that the material obtained as a result of interactions between 3AT and C60 fullerene may have extremely low dielectric constant around 1.6, so it could be considered as a candidate for ultra low-k (ULK) material applications. We prepared films composed of 3AT and fullerene by using two preparation techniques: spin-coating and evaporation. Interactions between these two components were investigated by using X- ray photoelectron spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS). We found that there are strong chemical reactions between the nucleophilic nitrogen atom from 3AT and electrophilic fullerene molecule. Results of NEXAFS measurements suggest that due to direct interactions between 3AT and C60 the shape of fullerene molecule is changed.}, language = {en} } @inproceedings{KolanekKaravaevTallaridaetal., author = {Kolanek, Krzysztof and Karavaev, Konstantin and Tallarida, Massimo and Schmeißer, Dieter}, title = {Atomic layer deposition of HfO2 onto SiO2 substrates investigated in-situ by non-contact UHV/AFM}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 248}, abstract = {We investigated in-situ the atomic layer deposition (ALD) of HfO2 onto SiO2 substrates with ultra high vacuum (UHV) non-contact atomic force microscope (NC-AFM). The ALD process was started after detailed analysis of the initial Si(001)/SiO2 substrate. The ALD cycles, made by using tetrakis-di-methyl-amido-Hf (TDMAHf) and water as precursors, were performed on the SiO2 substrate maintained at 230 ∘C. We studied the relation between the film growth and the root mean square surface roughness, surface skewness, kurtosis, fractal dimension and correlation length. In the initial stages of the ALD process with our analysis of the surface height histograms we were capable of determination: HfO2 layer thickness, surface coverage and surface roughness of a substrate and deposited material. Observation of the surface height histograms evolution during deposition allowed us to verify conformal and effective ALD growth on SiO2 substrate. With this detailed analysis of the surface topography we confirmed the completion of the first HfO2 layer after four ALD cycles.}, language = {en} } @inproceedings{MichlingTallaridaKolaneketal., author = {Michling, Marcel and Tallarida, Massimo and Kolanek, Krzysztof and Schmeißer, Dieter}, title = {In-situ EELS and UPS measurements on HfO2 ALD layers}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, abstract = {In this contribution we report on our in-situ cycle-by-cycle (up to 10 cycles) investigations of the HfO2 ALD process using the methods of EELS and UPS. We used TDMA-Hf as a precursor and p-type Si wafer with natural oxide as the substrate. The EELS measurements were done with a primary energy of 52,5 eV and the UPS measurements with He I (21,218 eV). The change in the onset of the loss function is readily observed. Already after two cycles the value approach to the bulk value of HfO2. Upon ALD growth there is a remarkable decrease in the intensity of states within the gap. They are rather smooth and saturate after 10 cycles. With UPS we follow the variation of the VB onset and changes in the secondary electron onset. We summarize our data in a band diagram not based on bulk values but on cycle dependent quantities. With these cycle-by-cycle experiments we study the initial growth of HfO2 especially in the very first cycles.}, language = {en} } @inproceedings{MuellerSchmeisser, author = {M{\"u}ller, Sebastian and Schmeißer, Dieter}, title = {Synchrotron radiation spectroscopy studies of the initial interaction between cobalt and titanium dioxide}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 652}, abstract = {Small metallic particles deposited on oxide surfaces can serve as heterogeneous catalysts, as for example TiO2 supported cobalt is a known Fischer-Tropsch-Catalyst. The goal of the presented studies is to investigate the interaction between cobalt and TiO2 in the initial step of growth by synchrotron radiation based spectroscopy. PES studies of TiO2 supported cobalt show a reduction of the oxide support, accompanied by an oxidation of the deposited material. The oxidation is not complete, but metallic cobalt is found already in the very first step of growth. Uniform decrease of both substrate PES lines indicate very weak interaction between overlayer and TiO2. An atomic multiplet calculation including charge transfer and crystal field effects is applied to simulate the experimental Co 2p XAS and XPS spectra of the oxidized component. The results allow the identification of the local coordination as well as the identification of the oxidation state of cobalt.}, language = {en} } @inproceedings{PhilipRichterFriedrichetal., author = {Philip, Shine and Richter, Matthias and Friedrich, Daniel and Paloumpa, Ioanna and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Spectroscopic investigations of P3HT/PCBM films for organic BHJ solar cells}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 153}, abstract = {Investigations of the electronic structure and composition of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) based films using Near Edge X-Ray Absorption Fine Structure (NEXAFS) are presented. The measurements were performed at the U49/2-PGM2 beam line of BESSY II, Berlin recording TEY (total electron yield) and TFY (total fluorescence yield) data. Samples prepared by spin coating a mixture of P3HT dissolved in chloroform and PCBM dissolved in chlorobenzene onto ITO (indium tin oxide) coated glass slides were analyzed. Upon measuring the pure P3HT and PCBM, all reported excitations were observed, whereas the blended system is a weighted superposition of the related peaks. Analyzing the data we calculate the composition of the mixture. We also show angular dependent NEXAFS measurements of the P3HT/PCBM blend in order to measure the orientation and distribution of the P3HT polymer. Additionally, we show a new approach for organic solar cell application. BaTiO3 nanoparticles were incorporated as nanodispersion into the donor-acceptor blend or the ferroelectric copolymer poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) was spincoated as an ultrathin film below the blend.}, language = {en} } @inproceedings{RichterFriedrichPhilipetal., author = {Richter, Matthias and Friedrich, Daniel and Philip, Shine and Paloumpa, Ioanna and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Study of P3HT/PCBM based films by NEXAFS}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 194}, abstract = {In this contribution we report on investigations of the electronic structure and composition of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) based films by using Near Edge X-Ray Absorption Fine Structure (NEXAFS). The measurements were done at the U49/2-PGM2 beam line of BESSY II, Berlin using TEY (total electron yield) and TFY (total fluorescence yield) detection. The samples were produced by spin casting a mixture of P3HT (dissolved in chloroform) and PCBM (dissolved in chlorobenzene) on ITO (indium tin oxide) coated glass slides. Measurements of pure P3HT and PCBM show all typical excitations, whereas the blended system is a weighted superposition of the related peaks. Analyzing these weighted superposition, we observe in the surface sensitive TEY data an accumulation of P3HT, whereas in the bulk sensitive TFY signal an as expected mixture is found. We also show angular dependent NEXAFS measurements of the P3HT/PCBM blend in order to measure the orientation and distribution of the P3HT polymer. Additionally, we will show a new approach for organic solar cell application by introducing ferroelectric nanoparticles into the mixture.}, language = {en} } @inproceedings{SchmidtSchmeisser, author = {Schmidt, Stephan and Schmeißer, Dieter}, title = {Cobalt/nickel mixed oxides - cathode materials for Li-Ion-Batteries}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 596}, abstract = {Replacing Co by large amounts of Ni is considered to reduce costs in Li-Ion-Batteries while maintaining their performance. We are interested in whether this replacement causes changes in the valence band (VB) and conduction band (CB) states or not. Samples were prepared as thin films from nitrate solutions on metal substrates and annealed in air and UHV. The Co to Ni ratio was varied from 50/50 over 40/60 and 30/70 up to 20/80. The results are compared to the pure Co-oxide. Experiments were carried out at the U49/2 beamline at BESSYII, Berlin. XPS of the TM2p states reveals the existence of charge transfer ground states and different oxidation states. NEXAS at the Co2p, Ni2p and O1s edges projects the density of unoccupied states while resonant PES at these edges provides the related partial density of states (pDOS) and thus can be used to distinguish between the different contributions of TM3d and O2p states in the valence band region. We find systematic variation of the VB structure, the valence band maximum and a shift at the O1s absorption edge while the TM2p XPS and absorption spectra do not seem to be affected by the mixing.}, language = {en} } @inproceedings{StarzykTallaridaSchmeisser, author = {Starzyk, Łukasz and Tallarida, Massimo and Schmeißer, Dieter}, title = {Electrically optimized high-κ metal gate MOSFET by specific modification of the band alignment}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 231}, abstract = {The electrical optimization of metal/oxide/semiconductor gate stacks by specific modification of the band alignment for advanced MOS technology incorporating high dielectric constant (κ) materials is explored. Because of requirements concerning continued scaling of MOSFET transistors, gate oxides and cobalt electrode have been grown successively on Si substrate respectively by means of atomic layer deposition (ALD) and evaporation. The thicknesses of high-κ films were around 2 nm. In case of work function engineering, interfaces' chemistry plays a fundamental role. We applied synchrotron radiation based x-ray photoelectron spectroscopy (SR XPS) to characterize our samples, which allows step by step in situ investigations. Co 2p, Al 2p, Hf 4f, Si 2p and O 1s core levels spectra were measured and analyzed. From valence band (VB) spectra we determined Schottky barrier height and electronic bands offsets.}, language = {en} } @inproceedings{WyrodekTallaridaSchmeisseretal., author = {Wyrodek, Jakub and Tallarida, Massimo and Schmeißer, Dieter and Weisheit, Martin}, title = {Determination of interfacial layers in high - k ALD nanolaminate materials by ARXPS and SRXPS measurements}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 232}, abstract = {The interfacial layers of high dielectric constant (high - k) nanolaminate films are here explored. Problems concerning ALD nanolaminate layers deals mainly with lack of accurate methods to determine in depth profile of few nm thick stacks. Modified angle resolved XPS(ARXPS) and synchrotron radiation XPS(SRXPS) are proposed as methods suitable in layer profiling. Studied stacks containing ZrO/HfO or AlO/ZrO, were prepared on Si substrates by atomic layer deposition (ALD). Two sets of experiments were covered. First dealt with initial growth (up to 20 cycles, with thickness d < 2nm) of AlO/ZrO and included layer by layer insitu investigation by SRXPS. Second experiment refer to industrial grown ZrO/HfO films ( d ∼ 3nm ) processed with various parameters resulting in both, layer by layer and homogenous depositions. For those samples exsitu XPS, with angle dependent variation of probing depth, measurements were covered. By comparing obtained intensity ratios for different angles with computational developed stack model it was found that no simple layer by layer but some intermixing growth occurred including interaction with silicon substrate.}, language = {en} } @inproceedings{BergholzSchmeisser, author = {Bergholz, Matthias and Schmeißer, Dieter}, title = {Band gap determination of thin Praseodymiumoxide layers on Aluminiumoxynitride films}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 243}, abstract = {High-k dielectrics are important as never bevore in semiconductor industry. We investigate Pr2O3 as one representative of this group on Silicon and Silicon-Aluminium oxynitride substrates. In earlier work we observed the positive influence of this AlOxNy intermediate layer on the electrical properties of the Pr2O3 layer. Now we present in-situ EELS, XPS and UPS measurements of gradually grown thin Pr2O3 on AlOxNy. From these measurements we determine the band structure and find a very fast change of the band gap for the first few {\AA}ngstr{\"o}m, coupled with n-type behaviour for the Pr2O3 film. These results are compared with RIXS measurements of a 5 nm Pr2O3 on a 1 nm thick AlOxNy layer.}, language = {en} } @inproceedings{BurkovHenkelSchmeisser, author = {Burkov, Yevgen and Henkel, Karsten and Schmeißer, Dieter}, title = {X-ray photoemission spectroscopy of Aluminium Oxynitride on Si(001) and the rise as buffer layers}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 243}, abstract = {Praseodymium oxide (PrxOy) is one of the candidate as high-k transistor gate dielectrics, but aluminium oxynitride (AlxONy) as buffer layer is needed to prevent diffusions from the silicon into PrxOy and to hinder charge injection from the semiconductor into the insulator. The thermal stability and thickness dependence of aluminum oxynitride (AlxONy) has been investigated by synchrotron radiation photoemission spectroscopy (SR-PES). AlxONy layers were prepared by low energy ion-beam assisted deposition (LE-IBAD) at room temperature on a silicon substrate cleaned with HF-acid. Aluminium oxynitride is stable till 800∘C. From photoemission spectra we can assess that silicon oxynitride is built as first and then the growth of AlxONy follows. Resonant inelastic X-ray scattering measurements with synchrotron radiation have been performed. The combination of X-ray absorption spectroscopy (XAS) and RIXS make possible to determinate the band gap of AlxONy.}, language = {en} } @inproceedings{HenkelSeimePaloumpaetal., author = {Henkel, Karsten and Seime, Bernd and Paloumpa, Ioanna and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {C(V) and C(t) measurements on MFIS structures consisting P[VDF/TrFE] as ferroelectric layer}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 828}, abstract = {Ferroelectric Field Effect Transistors (FeFETs) are considered as a candidate for future non volatile and non destructive readout memory cells. A possible low cost solution is the use of poly[vinylidene fluoride trifluoroethylene (P[VDF/TrFE]). Using P[VDF/TrFE] we focus on metal ferroelectric insulator semiconductor (MFIS) capacitor structures. In this contribution we will summarize our investigations related to capacitance measurements in dependence of applied bias (C(V)) and time (C(t)). The thickness of the ferroelectric layer as well as the thickness and the material of the buffer layer have been investigated for optimization of the write voltage. CV measurements at higher temperatures deliver decreased flatband voltage shifts within one CV loop resulting in lower memory windows. At temperatures around 100∘C the hysteresis totally vanished, pointing out the ferroelectric behavior of the system. C(t) measurements at a constant bias have been performed for retention analysis of the MFIS stack. After applying a writing pulse we could distinguish between a higher and a lower capacitance state for more than 5 days. This work is supported by Deutsche Forschungsgemeinschaft within priority program 1157 (SCHM 745/11-2).}, language = {en} } @inproceedings{KaravaevTallaridaSchmeisseretal., author = {Karavaev, Konstantin and Tallarida, Massimo and Schmeißer, Dieter and Zschech, Ehrenfried}, title = {In-situ ALD growth of Hafnium oxide films}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 244}, abstract = {We report on a novel system for in-situ atomic layer growth (ALD) of high-k dielectric films. First results were obtained for Hf-oxide samples by using Hf-tetrachloride as precursor and water as oxidizer. We compare the photoelectron spectra of Si2p, O1s and Hf4f of our in-situ prepared films with samples (ex-situ) prepared by industrial ALD reactors and discuss similarities and differences observed in the core level spectra of the various samples by considering the different growth conditions.}, language = {en} } @inproceedings{MandalMuellerSchmeisser, author = {Mandal, Dipankar and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Dipole orientation of the P[VDF-TrFE] co-polymer films: A NEXAFS study}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 840}, abstract = {Ferroelectric properties of copolymers of vinylidene fluoride with trifluoroethylene (P[VDF-TrFE]) has become great deal of interest due to potential use in non volatile memory technology. Permanent dipoles (formed between the alternating hydrogen and fluorine atom within the copolymer) ordering of orientation are crucial for device efficiency. Here we focus on thickness dependence dipole orientation in these co-polymer films. In our systematic studies, we found there is prominent dipole re-orientation effect also for the intrinsic films (~10 nm thickness) before applying the electric field. It is observed after the application of the field, the dipoles re-oriented in opposite direction. Therefore, we conclude that the lowest thickness of the film should have well grown crystalline lamellae structure. As a result, c-axis of crystallites acts as well define manner in plane of the surface and for that reason the b-axis is more free. Because the b-axis is parallel to the polarization direction, it is easy to get a preferred orientation of the dipoles. For thicker films (here up to 100 nm), the average orientation effect is hindered, so a very low re-orientation effect has been observed. For this investigation, we used Near Edge X-ray Absorption Spectroscopy, at the U 49/2-PGM beam line of BESSY-II, Berlin. This work is supported by DFG within SPP1157 (SCHM 745/11-2).}, language = {en} } @inproceedings{MuellerMandalHenkeletal., author = {M{\"u}ller, Klaus and Mandal, Dipankar and Henkel, Karsten and Paloumpa, Ioanna and Schmeißer, Dieter}, title = {Interface reactions of ferroelectric copolymer layers with different electrode materials}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 830}, abstract = {The ferroelectric copolymer poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) is a possible material for low cost applications as organic nonvolatile memory element. We present an XPS interface investigation of the copolymer/electrode interface. Below 100nm film thickness, interface phenomena becomes important. Possible interface reactions could lead to a reduction of the ferroelectric functionality.We present a comparative study of the two interfaces Al/P(VDF-TrFE) and PEDOT:PSS/P(VDF-TrFE). The result is a clear indication of a surface reaction in between the Aluminum-electrodes. In contrast, for PEDOT:PSS the measurements shows a layer by layer formation of the interface PEDOT:PSS/PVDF without any reaction. Second, we present a study of remanent polarization of ultrathin spincoated films of the copolymer, in a thickness range from 5 to 100mn, with organic electrodes like PEDOT:PSS. The measurements are carried out by using the flatband shift of a capacitance-voltage (CV) characteristic. This shift of flatband voltage is used as value for the electric polarization of the polymer.}, language = {en} } @inproceedings{MuellerSchmeisser, author = {M{\"u}ller, Sebastian and Schmeißer, Dieter}, title = {Direct Observation of d2L2 Charge Transfer States in TiO2 thin films by Resonant Photoelectron Spectroscopy}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 592}, abstract = {We investigate the electronic structure of TiO2 thin films by SR-PES, NEXAFS and ResPES. The films are prepared in a combined in-situ/ex-situ process that leads to stoichiometric thin films (≈ 10 nm) in Rutile structure. We focus on ResPES at the Ti 2p edge. When the photon energy is close to the Ti 2p absorption edge we observe additional features about 13 eV below the valence band main features. These features show clear spectator auger decay at the resonance leading to d0 final state. From this, we deduce the existence of the d2L2 initial charge transfer state as this is the only possible channel that enables the corresponding spectator auger decay. These features have the same origin as the satellite structures observed in core level spectra, esp. 2p and 3p.}, language = {en} } @inproceedings{TallaridaKaravaevSchmeisseretal., author = {Tallarida, Massimo and Karavaev, Konstantin and Schmeißer, Dieter and Zschech, Ehrenfried}, title = {Photoemission and absorption spectroscopy for in situ investigations of the ALD growth}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 242}, abstract = {We have investigated the growth of Hf-oxide on Si by means of photoemission and X-ray absorption spectroscopy using synchrotron radiation at Bessy, Berlin. The Hf-oxide layers were grown via atomic layer deposition (ALD) using an in-situ ALD reactor attached to the investigation chamber. The XPS and XAS spectra were measured after every deposition cycle by transferring the sample into the investigation chamber without breaking the vacuum. From the experimental data we have obtained information about the early stages of the Hf-oxide growth, concerning in particular the reactivity of the interface with Si. Due to the possibility to study the layers after every cycle and with different oxidation parameters without exposing them to contaminants, the in situ investigation revealed to be a very important method to understand the growth properties of Hf-oxide.}, language = {en} } @inproceedings{OpelNielsenBaueretal., author = {Opel, Matthias and Nielsen, Karl-Wilhelm and Bauer, Sebastian and Goennenwein, Sebastian T. B. and Gross, Rudolf and Cezar, Julio C. and Schmeißer, Dieter and Simon, J{\"u}rgen and Mader, Werner}, title = {Ferromagnetism and magnetic clusters in cobalt-doped ZnO}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 430}, abstract = {Ferromagnetic semiconductors (FMS) - i.e. semiconductors exhibiting long-range magnetic ordering - are intriguing materials. However, in spite of intensive research in the last decade, the existence of homogeneous FMS with a Curie temperature around or above room temperature still is controversial. A particularly tedious issue are local sample inhomogeneities or magnetic clusters, which can yield strong magnetic signals resembling the behaviour expected for a homogeneous FMS. Using pulsed laser deposition, we have grown cobalt-doped ZnO films on single crystalline ZnO substrates. Combining x-ray magnetic circular dichroism, DC magnetometry, and AC susceptibility measurements with a detailed structural analysis by high resolution x-ray diffraction, transmission electron microscopy, and electron-spectroscopic imaging, we can unambigously trace the characteristic, ferromagnetic-like behaviour of our ZnO:Co samples at room-temperature to nanometer-sized superparamagnetic metallic cobalt precipitates.}, language = {en} } @inproceedings{LazarevaKovalMuelleretal., author = {Lazareva, I. and Koval, Yuri and M{\"u}ller, P. and Paloumpa, Ioanna and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Field effect transistor of graphitized polyimide with P(VDF-TrFE) as gate insulator}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 195}, abstract = {Surfaces of polyimide films were graphitized by low-energy ion irradiation. The conductivity was between 10-5 to 200 S/cm [1]. We prepared field effect transistors using this material. Ferroelectric P(VDF-TrFE) was used as gate insulator. The thickness of P(VDF-TrFE) varied from 120 nm to 1200 nm. Properties of P(VDF-TrFE) were investigated by current-voltage measurements of metal/ P(VDF-TrFE)/metal capacitors. We have found that at room temperature, the coercive field of P(VDF-TrFE) does not depend on the film thickness. At lower temperatures the coercive field increases proportionally to the reciprocal temperature. Remnant polarization is 9.5 µC/cm2. It slightly rises with decreasing temperature. Our recent results of field effect mobility, carrier concentration and threshold voltage are presented. [1] I. Lazareva, Y. Koval, M. Alam, S. Str{\"o}msd{\"o}rfer, P. M{\"u}ller, Appl. Phys. Lett. 90, 262108 (2007)}, language = {en} } @inproceedings{BergholzSohalSchmeisser, author = {Bergholz, Matthias and Sohal, Rakesh and Schmeißer, Dieter}, title = {ELS to determine the band gap of thin dielectric layers}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 156}, abstract = {In ultra thin layers of high-K materials the value of the band gap can be derived not explicitly although it is a key quantity in the electric behavior. We use ELS with a monochromatized (50 meV - 150 meV) electron gun and primary energies between 20 eV and 30 eV. Starting with the native SiO2/Si(001) layers we find that loss function of the substrate dominates for using primary energies beyond 50 eV. In contrast at energies below 50 eV the loss intensity can be used to derived the band gap with an accuracy of ±200 meV. We compare thin (<3 nm) films of HfOx, Pr2O3,Al2O3 and Si-Oxynitrides and discuss the band gap values as well as the scattered intensity observed within the gap.}, language = {en} } @inproceedings{HenkelTorcheSchwiertzetal., author = {Henkel, Karsten and Torche, Mohamed and Schwiertz, Carola and Paloumpa, Ioanna and Sohal, Rakesh and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Inorganic and organic layers for high-k and organic memory applications}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 127}, abstract = {We report about organic and inorganic MIS stacks for new possibilities for high frequency and high power applications as well as for non volatile memory cell. The organic stack contains a ferroelectric polymer as the functional layer. Poly[vinylidene fluoride trifluoroethylene] (P[VDF/TrFE]) is spin coated from a solution onto oxidised silicon substrates. We report on the polarisation induced flatband voltage shifts. For the inorganic stack our attempt is to combine higk-k dielectrics with high band gap semiconductors (SiC). Praseodymium oxide layers are prepared by electron beam evaporation from Pr6O11 powder and in situ controlling of interface and volume composition (XPS). Praseodymium silicate layers were prepared either by metal evaporation onto a thin ox- ide on top of the semiconductor and following annealing steps or by a wet chemical process out of aqueous Pr(NO3)3 solutions. Using spectro-scopic characterisation we investigate the stability of the various inter-faces within the stacks as well as the reactivity of the metal electrodes on thin Pr2O3. We report the results of electrical characterisation consisting of permittivity values, leakage current and density of interface states.}, language = {en} } @inproceedings{MuellerHenkelPaloumpaetal., author = {M{\"u}ller, Klaus and Henkel, Karsten and Paloumpa, Ioanna and Schmeißer, Dieter}, title = {P(VDF/TrFE) as ferroelectric insulation layer for organic field effect transistors}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 101}, abstract = {The ferroelectric polymer poly(vinylidene fluoride trifluoroethylene)(P(VDF-TrFE)) is used as insulating material for organic field effect tran-sistors (OFET) and metal-insulator-semiconductor (MIS)-structures. For the MIS-structures, we find the typical hysteresis in the CV charac-teristic upon increasing the voltage scan window. Based on these results, we fabricate OFET with regioregular poly(3-hexlythiophene)(P3HT) as organic semiconductor. The transistors are constructed in bottom gate architecture with thin layers of spincoated P(VDF-TrFE) as gate insulation (100nm). The drain-source current of the OFET is reversible affected by the polarized gate, which gives opportunities for organic nonvolatile memory elements. We present characteristic features like the hysteretic drain current response or the data retention. Furthermore, we present measurements with Kelvin probe force microscopy, a method which gives informations on the lateral distributions of the surface potential.}, language = {en} } @inproceedings{HoffmannSchmeisserHimpseletal., author = {Hoffmann, Patrick and Schmeißer, Dieter and Himpsel, Franz J. and Engelmann, Hans-J{\"u}rgen and Zschech, Ehrenfried and Stegmann, Heiko and Denlinger, Jonathan D.}, title = {Characterization of Chemical Bonding in Low-K Dielectric Materials for Interconnect Isolation: XAS and EELS Study}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 41}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 41}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 156}, abstract = {The use of low dielectric constant materials in the on-chip interconnect process reduces interconnect delay, power dissipation and crosstalk noise. In CVD deposited organo-silicate glass (OSG) the substitution of oxygen in SiO2 by methyl groups (-CH3) reduces the permittivity significantly (from 4.0 in SiO2 to 2.6-3.3 in the OSG). However, plasma processing removes C and H containing molecular groups. Therefore, compositional analysis and chemical bonding characterization of structured films with nanometer resolution is necessary. OSG thin films as-deposited and after plasma treatment are studied using XAS and EELS. In both techniques, the fine structure near the C1s edge allows to identify C-H, C-C, and C-O bonds. XAS spectra have been recorded for non-patterned films and EELS spectra for patterned structures. The chemical bonding is compared for as-deposited and plasma-treated low-k materials. The flu-orescence and the electron yield recorded while XAS measurement are compared. Examination of the C 1s near-edge structures reveal a mod-ified bonding of the remaining C atoms in the plasma-treated sample regions.}, language = {en} } @inproceedings{MuellerChowdhuryDremovetal., author = {M{\"u}ller, P. and Chowdhury, F. and Dremov, V. and Koval, Yuri and Lichtenberg, F. and M{\"u}ller, S. and Schmeißer, Dieter and Pentcheva, R.}, title = {Resistive memory switching in perovskite-derivative single crystals}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 818}, abstract = {We investigated several layered perovskite derivatives of the family AnBnO3n+2, such as LaTiO3.41, CaNbO3.41 and SrNbO3.41, which can be considered as a stacking of blocks consisting of 5 perovskite layers. Electric transport across these layers takes place via intrinsic tunnelling. Mesa devices with a cross-sectional area of 50 to 200 µm2 and a height between 30 and 500 nm were fabricated by electron-beam lithography and ion-beam etching. Both dc I-V characteristics and pulsed current injection have shown switching between different resistive states in these materials. The resistive states have long-term stability, which makes them interesting for memory applications. The transport experiments suggest that switching and resistive memory are controlled by trapping and release of charge carriers. Furthermore, photoelectron and NEXAFS spectroscopy of cleaved LaTiO3.41 surfaces have been performed. The results are compared to recent correlated band theory (LDA+U) calculations.}, language = {en} } @inproceedings{SeifarthWalczykLupinaetal., author = {Seifarth, Olaf and Walczyk, Christian and Lupina, Grzegorz and Dabrowski, Jaroslaw and Weidner, G{\"u}nter and Zaumseil, Peter and Schmeißer, Dieter and Storck, Peter and M{\"u}ssig, Hans-Joachim and Schroeder, Thomas}, title = {On the electronic and dielectric characterisation of thin cubic PrO2 layers on Silicon}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 196}, abstract = {For the integration of 100 \% Ge onto the Si platform, a buffer oxide approach has been developed recently, using rare earth oxides to tune the lattice constant between the Si and the Ge. Among these buffer oxides, PrO2 is a prospective candidate with high quality crystalline growth on Si, moderated by an interfacial Pr-silicate between. In order to specify electronic properties of thin PrO2 and its interface on Si(111), especially the width of the band gap, we performed synchrotron radiation based XPS, UPS and XAS measurements at the U49/2 PGM 2 beamline at BESSY II and correlate the results with our structural characterisation performed by TEM and XRD. In order to evaluate the dielectric properties of thin PrO2 layers on Si(111), we performed temperature-, time-, voltage-, and layer thickness-dependent leakage current measurements (J-V). Here, we identified relaxation behaviour in the leakage current, successfully addressed to defect like states inside the Pr-silicate interface layer, corroborated by frequency dependent capacitance versus voltage (C-V) measurements.}, language = {en} } @inproceedings{FriedrichMichlingKloceketal., author = {Friedrich, Daniel and Michling, Marcel and Klocek, Jolanta and Schmeißer, Dieter and Avdoshenko, Stas and Chumakov, Dmytro and Zschech, Ehrenfried}, title = {Study of C60 based films formation by NEXAFS}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 145}, abstract = {The C60 fullerenes and some of its -OH, -CF3 and -Cl derivates are candidates for application as ultra-low-k insulators in the semiconductor industry. Future preparation of thin films based on these materials requires the stability of the substituted fullerenes against chemical handling and processing steps. The latter issue was addressed by our NEXAFS studies that were done by synchrotron radiation at the beam line U49/2-PGM2 at BESSY II. Performed were the C K-edge NEXAFS studies in total fluorescence and total electron yield modes. The C60 based films were deposited on silicon by spraying from solutions. The influence of the different substitutional groups with C60 molecules was studied. The data were compared to the reference spectra of a pure C60 film. For C60(OH)24, C60-Cl2 and C60(CF3)12 a variance of the intensity of the π*-resonance as well as shift to higher energies of 0.5 eV (-OH), 0.6 eV (-F), 0.7 eV (-Cl) were observed. The results confirm the necessary stability of the used C60 derivatives and shall be used for optimization of the film deposition chemistry and conditions.}, language = {en} } @inproceedings{KaravaevTallaridaSchmeisser, author = {Karavaev, Konstantin and Tallarida, Massimo and Schmeißer, Dieter}, title = {Evolution of the interfacial layer during the atomic layer deposition of HfO2 on Si/SiO2 substrates}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 160}, abstract = {We studied the formation of the interfacial layer in the Si/SiO2/HfO2 system using the in-situ Atomic Layer Deposition (ALD) reactor developed in our group [1,2]. We measured the X-ray photoelectron and X-ray absorption spectra with synchrotron radiation at the beamline U49-2/PGM2-BESSY II. The ALD growth was obtained using different Hf-precursors (HfCl4,TEMAHf and TDMAHf) on various prepared substrates at different temperatures. The investigation was carried out in-situ giving the possibility to determine the properties of the grown film after every ALD cycle without breaking the vacuum. We observed the evolution of the Si/SiO2/HfO2 system during the formation of first three Hf-oxide layers, detecting the interfacial growth of SiO2 during the initial ALD cycles from the XPS spectra of Si2p. We discuss how the interfacial layer growth depends on the various ALD parameters. [1] M. Tallarida, K. Karavaev, and D. Schmeisser, J. Appl. Phys. 104, 064116 (2008); [2] M. Tallarida, K. Karavaev, and D. Schmeisser, J. Vac. Sci. Technol. B, accepted for publication.}, language = {en} } @inproceedings{KolanekKaravaevTallaridaetal., author = {Kolanek, Krzysztof and Karavaev, Konstantin and Tallarida, Massimo and Schmeißer, Dieter}, title = {In-situ investigations of the atomic layer deposition of HfO2 with UHV/AFM}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 160}, abstract = {We studied in-situ the atomic layer deposition (ALD) of HfO2 with ultra high vacuum (UHV) atomic force microscope (AFM), using the ALD reactor developed by our group [1, 2]. The reactor was attached to the Omicron Large Sample-UHV/AFM system in the AFM-Lab of the Angewandte Physik-Sensorik chair at the BTU-Cottbus. We investigated different Si(001)/SiO2 substrates and surface preparation techniques performed before the ALD process. After each ALD cycle (using TDMAHf and H2O as precursors), we studied the influence of the HfO2 growth on the root mean square (RMS) roughness; the surface fractal dimension and the height histogram: the surface skewness and kurtosis. We focused on the influence of the substrate temperature on the surface topography during the ALD. The in-situ studies of the ALD process with the UHV/AFM system correlated with the experiments performed with photoelectron spectroscopy can be used for understanding the fundamental properties of the ALD of HfO2 on Si(001). [1] M. Tallarida, K. Karavaev, and D. Schmeisser, J. Appl. Phys. 104, 064116 (2008); [2] M. Tallarida, K. Karavaev, and D. Schmeisser, J. Vac. Sci. Technol. B, accepted for publication.}, language = {en} } @inproceedings{KraatzSchmeisserZschechetal., author = {Kraatz, Matthias and Schmeißer, Dieter and Zschech, Ehrenfried and Ho, Paul S.}, title = {Electromigration simulation for on-chip Cu interconnects}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 161}, abstract = {We are investigating the influence of copper microstructure on electromigration degradation effects and interconnect lifetimes using computer simulation. The simulation is carried out in three dimensions. For the copper microstructure, a Monte Carlo technique was used to model the Cu grain growth. Different diffusivities where applied to grain boundaries and top interface of the interconnect model according to the qualitative crystallographic orientation of adjacent grains. The grain boundary network and the top interface form the diffusion paths for the electromigration mass transport. Along the diffusion paths, the fluxes of vacancies where calculated including mechanical stress and electromigration driving forces using a finite difference method. Positive flux divergent sites of the FDM lattice are treated as void nucleation sites after a critical vacancy concentration is reached. The resistance increase due to void growth was calculated using a cellular automaton, masking current free regions as quasi voids and adding the resistance of the slices of the lattice normal to the electron flow direction in series. A parallel computing environment was used to generate large numbers of interconnect models in order to obtain a pool of data for statistical analysis of interconnect lifetimes. The results of this analysis will be shown}, language = {en} } @inproceedings{MichlingFriedrichSchmeisseretal., author = {Michling, Marcel and Friedrich, Daniel and Schmeißer, Dieter and Koval, Yuri and M{\"u}ller, Paul}, title = {Study of polyimide after graphitization with low-energy Ar+ Ion irradiation by NEXAFS}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 147}, abstract = {In this contribution we report on investigations of the electronic structure of Ar+ irradiated polyimide samples by using NEXAFS. The NEXAFS measurements were done at the U49/2-PGM2 beam line of BESSY II, Berlin using TEY and TFY detection. Polyimide samples are prepared using low Ar+ dose while the temperature of the samples is varied between 300K and 700K. In the NEXAFS data at the Carbon K-edge we see substantial changes between different samples. The differences appear in particular in the more surface sensitive TEY-Signal. The NEXFS data are consistent with the graphitization of the surface upon Ar+ bombardment as we identify the characteristic absorption bands of graphitic carbon. Its relative content increases with increasing sample temperature. In contrast, in the more bulk sensitive TFY data, the emission characteristic of polyimide is maintained. The possibility to cover insulating polymers with a conducting layer is a great demand for many applications. Because of the relative low price of the basic materials, the irradiation with low-energy Ions will play an important roll in the microelectronic of the future.}, language = {en} } @inproceedings{MuellerSchmeisser, author = {M{\"u}ller, Sebastian and Schmeißer, Dieter}, title = {Investigation of ultra-thin Chromium layers on Titanium Dioxide by resonant photoemission}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 453}, abstract = {Oxide supported metal films and clusters offer interesting properties with a wide range of possible applications. In this context, Titanium Dioxide is chosen as a model substrate due to its simple electronic structure with a d0 configuration. We study the interaction of ultrathin Chromium films deposited on TiO2 film with focus on the modifications of the valence band and band gap region. Normal photoemission in bulk and surface sensitive modes as well as resonant photoemission at the Cr 2p and Ti 2p edges are used to distinguish the different Cr 3d and Ti 3d contributions to the valence band. In the initial step we find to gap states of distinct character with a sharp resonance of the Cr 3d related state at the Cr 2p edge. With increasing layer thickness we observe that this resonance extends to about 20 eV below the Fermi-Energy. Datasets of valence band spectra measured around the Cr 2p edge show 2 resonant mechanisms in this case i.e. a participator channel for the 3d state accompanied by a spectator channel at fixed kinetic energy.}, language = {en} }