@inproceedings{GoryachkoBeuckertZaumseiletal., author = {Goryachko, Andriy and Beuckert, Guido and Zaumseil, Peter and Wagner, Guenter and Schmeißer, Dieter}, title = {Investigations of Pr2O3 growth modes on 4H-SiC(0001) Surfaces}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, isbn = {ISSN 0420-0195}, abstract = {The SiC is suited especially well for high power and high voltage semiconductor devices. In order to increase the reliability against electrical breakdown of metal-insulator-semiconductor (MIS) structures, one needs to use the insulator with possibly higher dielectric constant. Pr2O3 is shown to posses a much higher dielectric constant (equals 30) than traditionally used SiO2. Therefore, Pr2O3/SiC is an excellent material combination for high voltage MIS devices. The 4H-SiC(0001) substrates are characterised with scanning tunneling microscopy, while the Pr2O3 surface - with atomic force microscopy technique. We show distinct growth modes of Pr2O3 film, such as 3D and layer by layer growth. The crystalline structure and film thickness are determined by X-ray diffraction and its chemical composition by X-ray photoelectron spectroscopy. The Pr2O3 film characteristics are optimised for high-quality MIS structures in terms of lateral uniformity, low interface states density and leakage current, as well as physical integrity.}, language = {en} } @inproceedings{HoffmannSchmeisser, author = {Hoffmann, Patrick and Schmeißer, Dieter}, title = {Growth of oxynitrides on Si-rich 4H-SiC(0001) surfaces}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {It will be reported on the growth of oxynitride thin layers (≤10nm) on (0001)-oriented 4H-SiC surfaces. The oxynitride layers were grown by a thermal treatment of the samples in low pressure N2O ambient. By varying the growth conditions (N2O pressure, sample temperature, growth time) different layers were made. The grown layers were investigated by photoelectron spectroscopy (XPS) for chemical analysis and by AFM/STM for analysis of the surface morphology. Concerning the chemical analysis it will be discussed the general nitrogen content of the samples, the composition of the films (e.g. content of silicon nitride Si3N4 and silicon oxynitride SiOxNy) and the sub-oxides which build the interface between SiC and the oxynitride layers. Concerning the surface morphology mainly the roughness will be discussed. The so obtained results for oxynitride thin films on 4H-SiC will be compared to similarly prepared oxynitride layers on Si(111) investigated in the past.}, language = {en} } @inproceedings{MuellerBurkovSchmeisser, author = {M{\"u}ller, Klaus and Burkov, Yevgen and Schmeißer, Dieter}, title = {Spectromicroscopic Characterisation of All Polymer Transistor Structures}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {In order to optimize organic field effect transistors, the characterization of surfaces in terms of their roughness or chemical composition is very important. We report on high resolution spectromicroscopic mapping of organic thin film transistors by photoemission electron microscopy (PEEM). It was shown that PEEM is a useful technique to characterize the surface morphology (roughness), the chemical homogeneity or the composition of structures in between the source and drain electrodes. Mapping of surface potentials, especially at the interface electrode/channel is possible. We compare different preparation methods and the characterization at applied voltages is also shown. The transistors itself were prepared by a new low cost method. The electrodes for source and drain have been prepared by a plotting method with colloidal graphite or carbon black as the conducting material. P3HT was used as active layer and has been prepared by spin coating.}, language = {en} } @inproceedings{MuellerPaloumpaSchwiertzetal., author = {M{\"u}ller, Klaus and Paloumpa, Ioanna and Schwiertz, Carola and Jahnke, Agnes and Schmeißer, Dieter}, title = {All Polymer Field-Effect-Transistors based on Low-Cost-Microstructuring}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Thin film transistors with P3HT as active layer have been prepared by spin coating. The electrodes for source and drain have been prepared by a low cost plotting method with colloidal graphite or carbon black as the conducting material. PEDOT or carbon black was used as gate electrode. The devices, prepared by different methods and materials have been characterized by electrical measurements, for example, their transfer and output characteristics. Furthermore, the influence of different materials on effects like hysteresis or reproducibility will be compared. In addition, we describe a project investigating new types of biosensors with functionalized gate electrodes. Exchanges of dipole moments or charges by immobilisation of biomolecules will change the electrical characteristic of the transistor, which leads to a sensing signal proportional to their amount.}, language = {en} } @inproceedings{TorcheMuellerHenkeletal., author = {Torche, Mohamed and M{\"u}ller, Klaus and Henkel, Karsten and Lupina, Grzegorz and Goryako, Andrey and Wollweber, J{\"u}rgen and Schmeißer, Dieter}, title = {Investigations of 3C-SiC growth on Si (001)}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Carbide was grown on Si (001) - substrates with supply of C2H2. Investigation of the interface Si/SiC (buffer layer) is essential for optimized preparation conditions, leading to a high quality of the growing SiC crystal. In addition to the lattice mismatch of 20 per cent between Si and SiC, which causes defects like dislocations or stacking faults, the chemical homogeneity of this layer is important. XPS was used to characterize the first state of SiC crystal growth on the Si substrate. Carbonizing with C2H2 leads to surface reactions which build up the buffer layer. By using electron spectroscopy, it was possible to characterize the SiC/Si (001) buffer layer, depending on the following reaction parameters: Tsubstrate , PC2H2 , PH2 , the ratio of pressures and the reaction time. The measurements were performed in terms of the content of carbide, oxide and roughness/etching-efficiency (Profilometer) for the reaction parameters above. We found, that the most critical parameter is the temperature of the substrate (Tsubstrate).}, language = {en} } @inproceedings{SchmeisserMuessig, author = {Schmeißer, Dieter and M{\"u}ssig, Hans-Joachim}, title = {Stability and electronic properties of silicates in the system SiO2 - Pr2O3 - Si(001)}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Hetero- oxides are the candidates to replace SiO2 as the gate dielectric material for sub-0.1µm CMOS technology. In particular, the basic interaction mechanisms at the interface are a key issue and a solid knowledge of these mechanisms is required to address reliability issues. The challenge in material science is to understand the chemical bonding of the hetero oxides and Si on a microscopic scale. This report focuses on the interaction of the high dielectric constant (DK) material Pr2O3 with SiO2 and the bare Si(001) surface. Photoelectron spectroscopy (PES) using tunable Synchrotron radiation (undulator U49/2 at BESSY II) is shown to provide spectroscopic information which is used for characterization of the electronic structure elements at the interface as well as for a non-destructive depth profiling. The chemical state of the Si atoms at the interface is identified and the chemical stability of the various oxide phases is discussed. We determine the variation of the elemental composition across the interface and follow the stability of the silicate phase.}, language = {en} } @inproceedings{HoffmannSchmeisser, author = {Hoffmann, Patrick and Schmeißer, Dieter}, title = {Depth Profiling of Ultrathin Oxynitride Layers Using Synchrotron Radiation}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {To determine the depth structure of samples various destructive (SIMS, depth profiling with sputtering and AES or XPS) and non-destructive techniques (RBS - Rutherford-Back-Scattering) are available. But all methods are less suitable for investigating especially ultrathin (<5nm) layers: While the destructive techniques suffer from Ion-mixing the RBS can not deliver chemical information. Due to the depth-dependent attenuation of photo-electrons XPS also contains depth information. As XPS gives only a sum signal across the layer one needs to modify the Inelastic Mean Free Path (IMFP) of the photo-electrons to vary the depth information in the photo-electron spectra. This can be done by changing the kinetic energy with the use of different excitation energies delivered from a Synchrotron. Using this method we were able to investigate the chemical depth structure of silicon oxynitride layers. The layers were grown on Si(111) by a N2O-treatment. The depth profile of that layer shows a silicon nitride layer forming the interface between the silicon substrate and the oxynitride.}, language = {en} } @inproceedings{MuellerSchmeisser, author = {M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Elektronenspektroskopie an Kupferindiumdisulfid Oberfl{\"a}chen}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {In diesem Beitrag wird eine Studie vorgestellt, welche die elektronenspektroskopische Untersuchung von CIS-Oberfl{\"a}chen f{\"u}r Solarzellen zum Thema hatte. XPS-UPS Analysen von Cu-reichen CuInS2-D{\"u}nnfilmen zeigten, daß die Variationen der Elementverh{\"a}ltnisse im Verlauf eines kontrollierten Heizprozesses entlang bin{\"a}rer Schnitte des tern{\"a}ren Phasendiagramms Cu-In-S verlaufen. Die Elementverh{\"a}ltnisse bei zus{\"a}tzlich aufgedampftem Kupfer und erh{\"o}hter Temperatur f{\"o}hrten in den Homgenit{\"a}tsbereich von CuInS2. PEEM-Untersuchungen zur Probenmorphologie zeigten, daß ein Sinterprozess w{\"a}hrend der Temperung der Proben bis 550 C und einer Belegung mit Kupfer erfolgt. Mit Differenz-PEEM-Aufnahmen konnten kupferreiche Fremdphasen wie CuS an der Oberfl{\"a}che sichtbar gemacht werden. Die in-situ Charakterisierung des Oberfl{\"a}chenchemismus im Verlauf der Temperung zeigte eine zunehmende Homgenit{\"a}t der Elementverteilung, was auf einen geringer werdenden Anteil von Fremdphasen hindeutet. NEXAFS-Aufnahmen ergaben erstmals Informationen {\"u}ber die Bandstruktur oberhalb der Fermienergie und ebenfalls Hinweise auf Fremdphasen sowie deren Reaktionen bei h{\"o}heren Temperaturen.}, language = {de} } @inproceedings{StyervoyedovPaloumpaSchmeisser, author = {Styervoyedov, Andriy and Paloumpa, Ioanna and Schmeißer, Dieter}, title = {Composition and thermal stability of thin functional oxidic (Pr, La, Y) and metallic (Ru, Ti) layers on Si and SiC substrates}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Thin Pr-, La- and Y- based oxide layers for applications as gate dielectric in metal-oxide-semiconductor (MOS) structures are investigated with x-ray photoelectron spectroscopy. The films with a thickness of around 2nm have been prepared on Si and SiC wafers by various chemical deposition methods based on nitrate solutions. In addition, we report on Ti- and Ru- based metal contacts prepared in the same way. The film composition is analysed and annealing steps in vacuum up to 900∘C have been applied to test their thermal stability. The interface characteristics, surface composition and thermal stability of MOS functional multilayers have been studied and will be presented.}, language = {en} } @inproceedings{Schmeisser, author = {Schmeißer, Dieter}, title = {The initial interaction of Pr2O3 to (001) and (111) oriented Si substrates}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {The high surface sensitivity of synchrotron based core level spectroscopy is employed to study the initial growth of Pr2O3 on Si(001) and Si(111) substrates. The Si2p core levels are different for the two substrates when the exposure is below 1nm. The core level shifts indicate a single bonding of the oxide on the terminal Si atom in Si(111) while on Si(001) the two dangling bonds are reactive. On both surfaces a significant broadening in the substrate emission is found and interpreted in terms of non bonding Si atoms located at the interface. Upon increasing the Pr2O3 exposure above 1nm the Si back bonds in the first Si layer are attacked to form Si - O - Pr bonds which cause a silicate like core level shift.}, language = {en} } @inproceedings{LupinaSchroederDabrowskietal., author = {Lupina, Grzegorz and Schroeder, Thomas and Dabrowski, Jarek Marek and Schmeißer, Dieter and M{\"u}ssig, Hans-Joachim}, title = {Ti-doping of Pr silicate layers for high-k dielectrics applications}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Near-term downscaling of the metal-oxide-semiconductor field-effect transistors (MOSFETs) requires the replacement of the SiO2 gate oxide with a material having a higher dielectric constant. Recent studies indicate that silicate materials are the most promising candidates; among them are Pr silicates. Applying a combination of x-ray photoelectron spectroscopy (XPS), electrical measurements (C-V), and ab initio calculations, we investigated the effect of thin Ti doping on the structural and electrical properties of the gate stacks composed of a Pr silicate film and a SiO2-based interfacial buffer layer. Metallic Ti was deposited at room temperature after the formation of the Pr silicate dielectric. The resulting layered structures were annealed under ultra-high vacuum (UHV) at various temperatures between 70∘C and 880∘C. XPS indicates that the evaporated layer preserves its metallic character over the whole range of UHV annealing temperatures. Synchrotron radiation XPS at BESSY II shows that large amounts of Ti atoms incorporated into the Pr silicate remain metallic even after air exposure at room temperature. Annealing in nitrogen ambient at 300∘C leads to the oxidation of these atoms so that a mixed Pr:Ti silicate is formed. We show that the so formed dielectrics exhibit an improved equivalent oxide thickness and a reduced density of interface states.}, language = {en} } @inproceedings{HenkelPaloumpaMuelleretal., author = {Henkel, Karsten and Paloumpa, Ioanna and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {P(VDF/TrFE) as a ferroelectric dielectric for Organic Field effect Transistors in MFIS structure}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {MFIS structures consisting of metal, ferroelectric poly[vinylidene fluoride trifluoroethylene](P[VDF/TrFE]), insulator, semiconductor (Si) are fabricated and the influence of the polarization of the P(VDF/TrFE) on the CV characteristics of these structures is investigated. We find a characteristic ferroelectric hysteresis in the CV curves upon increasing the voltage scan window (e.g.-U...U,U=6...30V, |UP(VDF/TrFE)|≤15V, dP(VDF/TrFE)=300 nm). A writing process with adequate electric fields causes large shifts in the flatband voltage ( Δ UFB>4V for the quoted example before) which are stable over days. We report on our investigations which focus on the switching behavior by varying the parameters like polymer thickness, writing field strength and time, long time stability, reversing voltage and insulating material (SiO2, PMMA (Polymethylmetacrylate)). This material combination is favorable for transfer into our full organic concept of field effect transistors for application as a nondestructive readout memory (NDRO) cell.}, language = {en} } @inproceedings{MuellerBurkovSchmeisser, author = {M{\"u}ller, Klaus and Burkov, Yevgen and Schmeißer, Dieter}, title = {Surface potential profiling on organic thin film transistors by photoemission-electron-microscopy (PEEM)}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Surface potential imaging with Photoemission-electron-microskopy (PEEM) in high lateral resolution is introduced as a new tool for the characterisation of organic transistor structures. We use source-drain- electrode structures of different organic materials like carbon-black or graphite plotted on a printing foil. Semiconducting regioregular Poly(3-Hexylthiophene-2,5-diyl) (P3HT) was deposited by spin coating. For our measurements we used radiation of a standard high pressure Hg-lamp (4,9 eV) and synchrotron radiation at the BESSYII-U49/2 beam line. In contrast to Kelvin-AFM measurements of the surface potential, PEEM enables a simultaneous analysis of chemical composition by photoelectron spectroscopy. UPS, for example, at zero potential gives information on chemical homogeneity of the organic semiconductor in lateral resolution. PEEM images at applied voltages, compared with UPS-spectra, gives informations on doping profiles in the semiconductor, for example. In conclusion, PEEM should be a complementary method for characterisation of the surface potential with Kelvin-AFM. In addition, PEEM gives opportunities for measurements of chemical composition in the working state of the transistor (applied voltages).}, language = {en} } @inproceedings{MuellerPaloumpaHenkeletal., author = {M{\"u}ller, Klaus and Paloumpa, Ioanna and Henkel, Karsten and Schmeißer, Dieter}, title = {Organic Field Effect Transistors with polymer high-k dielectric insulator}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Organic field effect transistors consisting of the copolymer poly(vinylidene fluoridetrifluoroethylene) (P(VDF-TrFE)) and P3HT (poly(3-hexlythiophene)) as active layer have been fabricated. The influence of P(VDF-TrFE) on the transconductance of organic field effect transistors was investigated and enhanced gate effects are observed compared to similar transistors with PMMA (Polymethylmetacrylate) as gate dielectric. Due to the high dielectric constant of P(VDF-TrFE) (DK=12) an operation voltage smaller than for a conventional organic dielectric like PMMA (DK=3.3) was observed. The thickness of the spincoated dielectric layers is in the range of 2microns and in consequence, no significant hysteresis was found, a prerequisite for transistor operation.}, language = {en} } @inproceedings{GeussMuellerPaloumpaetal., author = {Geuss, Markus and M{\"u}ller, Klaus and Paloumpa, Ioanna and Schmeißer, Dieter}, title = {Surface Potential profiling on operating full organic thin film transistors by Kelvin probe force microscopy}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Kelvin-AFM is employed to study all polymer organic thin film transistors which are promising candidates for low cost - low performance applications like active matrix displays, sensors or single-serving devices. We use bottom contact source-drain- electrode structures of different organic materials like carbon-black or graphite plotted on a printing foil. Semiconducting regioregular Poly(3-Hexylthiophene-2,5-diyl) (P3HT) was subsequently deposited by spin coating. Surface potential profiles across the transistor channel were measured by Kelvin-AFM for various source-drain potential differences and signs. We found that contact resistances cause characteristic steps in the surface potential near the channel edges which vary with the electrode material. Furthermore, nonlinearities appear in the potential gradient which possibly give evidence for lateral inhomogeneities of the carrier mobilities. In summary, surface potential imaging with high lateral resolution ( approx. 100 nm) is introduced as a powerful tool for the characterisation of the transistor performance and the selection of suitable low cost electrode materials.}, language = {en} } @inproceedings{TorcheSchmeisser, author = {Torche, Mohamed and Schmeißer, Dieter}, title = {The interaction of Al, Au, Ag, and Ti metal contacts with Pr2O3 thin films}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Pr2O3 is one of the promising high-k oxides desirable to replace SiO2 for the sub-100nm field-effect transistors (FETs) and dynamic random access memory (DRAM) capacitors. Here we focus on the metallic contacts used for the MOS and MIM based structures. With the thickness of Pr2O3 being around 3nm the metal interaction is crucial to avoid a reduction of the dielectric properties by metal percolation, crack filling or diffusion processes. We use XPS and SRPS to study the initial interaction as well as the thermal stability of metals (Al, Ag, Au, and Ti) on Pr2O3 films. We show that Al, Ag, Au form initial metallic layer which react already at temperatures around 300∘C. In contrast, Ti is found to be more stable than the other metals. We determine the formation of Ti-oxides at the Ti / Pr2O3 interface and its thermal stability. Ti is found to build a good diffusion barrier between the oxide and the metal.}, language = {en} } @inproceedings{SeifarthBurkovSchmeisseretal., author = {Seifarth, Olaf and Burkov, Yevgen and Schmeißer, Dieter and Sydorenko, Alexander and Krenek, Radim and Stamm, Manfred}, title = {Photoelectron spectroscopy and microscopy on magnetic nano particles embedded into block copolymers}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {The formation of metallic nano particles stored in thin films of block copolymers has been investigated by means of synchrotron radiation based photoemission spectroscopy (PES) and microscopy (PEEM). Empty channels in poly(styrene-block-4-vinylpyridine) copolymer with diameters of tens of nanometers filled with CrO2, Cr2O3 and Ni provide ideal bases for performing electron spectroscopy with energy and lateral resolution on magnetic nano particles. We present UPS, XPS, NEXAFS spectra and PEEM images on and off the C 1s, Cr 2p, Ni 2p resonances and discuss the geometric and electronic structure of such compounds. The synchrotron radiation was delivered from the U49/2 beamline at BESSY II.}, language = {en} } @inproceedings{MikaloAppelHoffmannetal., author = {Mikalo, Ricardo Pablo and Appel, G{\"u}nter and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Conducting Polypyrrole doped with Phthalocyaninesulfonates - new materials for chemical sensors}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Polypyrrole - a conducting polymer - is used as an active electrode of a quartz micro ballance and considered as a gate electrode in all-polymer field effect transistors used as chemical sensor. We use substituted phthalocyanines as dopants of polypyrrole as they offer the possibility to enhance the dopant concentration as well as to include functionalized groups. We studied these films by photoelectron spectroscopy, NEXAFS, PEEM, and TEM. These investigations revealed that the electronic structure as well as the morphology are highly dependent on the dopant's structure. We suggest a new charge transport model for 5-ring heterocycle conductive polymers. Whereas in the standard model only the carbon backbone is considered for the charge transport, we found by NEXAFS investigations that the heteroatom has a considerable high participation in the gap states, which are responsible for the charge transport. The dopants π-interactions force the nitrogen lone pair wave functions to contribute to the conducting polymer π-system. This is a novel approach concerning the application as chemical sensors since the reversible interaction of the analyte modifies the dopant and not the matrix.}, language = {en} } @inproceedings{BatchelorFollathSchmeisser, author = {Batchelor, David R. and Follath, Rolf and Schmeißer, Dieter}, title = {Design of a PGM for the U49/2 Undulator at BESSY II}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {This poster describes the beamline proposed for the BESSY II U49/2 Undulator by the Collaborating Research Group of BTU Cottbus, HMI Berlin and the TU Darmstadt. The beamline is designed with both high resolution electron spectroscopy, valence band measurements and PEEM in mind and utilises the wide energy range of the U49 Undulator 40-1500eV. The design chosen is based on a Petersen PGM [1] but with the grating illuminated with parallel light [2]. This modification allows variation of the monochromator higher order content or resolution, spot size without changing the focus. The performance of the beamline was investigated using various programs available at BESSY. The Undulator character- istics were evaluated using both SMUT and WAVE, and the optical performance of the monochromator was checked using REFLEC and RAY. The calculations show a resolving power of 2×104 with a flux of the order 1013 photons s-1 over the energy range covered by the mono- chromator. The maximum nominal second order contributions are ≈ 2\% at 300 eV for the first Undulator harmonic and ≈ 9\% for the third harmonic at 500 eV, both of which can be reduced by increasing the grating incidence angle and, or decreasing the Undulator Pinhole size.}, language = {en} } @inproceedings{HellerSchmeisser, author = {Heller, Thomas and Schmeißer, Dieter}, title = {Polaronen in SrTiO3(100)}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Vorgestellt werden Untersuchungen zur elektronischen Struktur von oxidischen Halbleitern wie SrTiO3(100)-Einkristallen und WO3-Filmen. Die Charakterisierung der Oberfl{\"a}chen erfolgt im Valenzbandbereich mittels Photoelektronenspektroskopie (TGM 7, Bessy I, hν=3D 15-100eV). Zust{\"a}nde entstehen in der Bandl{\"u}cke dieser=20 Materialien durch Dotierung (Heizen oder Natrium-Belegung). Wir untersuchen den Wirkungsquerschnitt speziell f{\"u}r diese Gapzust{\"a}nde. Ohne Dotierung ist der Verlauf des Wirkungsquerschnittes unstrukturiert. Bei Dotierung bilden sich molekulare Resonanzen. Deren Auftreten zeigt, daß diese Gapzust{\"a}nde lokalisiert sind. Weiterhin beobachten wir ausgepr{\"a}gte Feinstrukturen, die die charakteristische Anregung f=FCr Polaronen enthalten.}, language = {de} } @inproceedings{HoffmannBoehmeSchmeisseretal., author = {Hoffmann, Patrick and B{\"o}hme, Oliver and Schmeißer, Dieter and Lloyd Spetz, Anita and M{\aa}rtenson, Per}, title = {Einfluß von Nanopartikeln auf die Funktion von Hochtemperatursensoren}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Es werden Untersuchungen an als Hochtemperatur-Sensoren arbeitenden Schottky-Dioden mit dem Aufbau Metall-Oxidschicht-Siliziumkarbid vorgestellt. Dazu wurden Tiefenprofile mit XPS durch abwechselndes Abtragen durch Sputtern und Messen erstellt. Die Messungen erfolgten an thermisch unterschiedlich vorbehandelten Proben. Dabei konnten dipol-bedingte Verschiebungen der Bindungsenergie von Rumpfniveaus beobachtet werden. Das dazu notwendige Dipol-Moment wird durch das Entstehen von mit einer Oxidschicht {\"u}berzogenen Nanoteilchen erkl{\"a}rt. Die unterschiedlich ausgepr{\"a}gten Dipol-Verschiebungen auf den einzelnen Proben erlaubten eine Erkl{\"a}rung der thermischen Vorbehandlung, die bei Weglassen zu „frischen" und je nach Temperatur zu „aktivierten" oder „toten" Sensoren f{\"u}hrte.}, language = {de} } @inproceedings{MikaloAppelHoffmannetal., author = {Mikalo, Ricardo Pablo and Appel, G{\"u}nter and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Leitf{\"a}higes Polypyrrol als Elektrodenmaterial: Wechselwirkungen mit Silber}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Untersuchungen des metallischen Kontaktes von Silber auf tosylat- und phthalocyanindotiertem Polypyrrol wurden mittels XPS- und µ-NEXAFS vorgenommen. Es wurde festgestellt, daß Silber mit dem Polypyrrol keine Verbindung eingeht. Daraus kann geschlossen werden, daß sowohl das leitf{\"a}hige Polymer, als auch das Silber ihren Leitf{\"a}higkeitsmechanismus beibehalten. Es konnte gezeigt werden, daß bei steigender Silberbelegung die Intensit{\"a}t der Polaronenzust{\"a}nde des Polypyrrol in st{\"a}rkerem Maße abnimmt, als die Intensit{\"a}t der unbesetzten Zust{\"a}nde. Das l{\"a}ßt darauf schließen, daß Silber die Grenzfl{\"a}che stabilisiert.}, language = {de} } @inproceedings{OpreaSchmeisserGoldenblum, author = {Oprea, Alexandru and Schmeißer, Dieter and Goldenblum, A.}, title = {On the charge transfer process in ZnS based ac powder electroluminescent devices}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {The charge transfer process in ZnS based ac powder electroluminescent devices was experimentally and theoretically investigated. The time dependence of active currents and the voltage dependence of the brightness were measured in different operating conditions. This data allowed the hypothesis that each ZnS grain of the ac powder electroluminescent device (PWELD) behaves as a thin films electroluminescent device (TFELD) with metal-insulator-semiconductor-insulator-metal (MISIM) structure. The whole PWELD, itself, can be considered as a sum of many litle MISIM sandwiches electrically conected among them and having the quasi Fermi level of the semiconductor-insulator interface randomly distributed. On this basis, in the frame of a statistical Monte-Carlo like procedure, was developed a quantative semiclassical model, in good agreement with the experimental data.}, language = {en} } @inproceedings{HellerBoehmeSchmeisser, author = {Heller, Thomas and B{\"o}hme, Oliver and Schmeißer, Dieter}, title = {Gap - Zust{\"a}nde in Wolframoxid WO3 - relaxierten Oberfl{\"a}chen}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Vorgestellt werden Arbeiten an d{\"u}nnen WO3-Schichten, die durch Verdampfen aus einer Knudsenzelle im UHV pr{\"a}pariert wurden. Diese Filme sind im Rahmen der XPS-Analysen st{\"o}chiometrisch, ohne Gap-Zust{\"a}nde. Definierte Gap-Zust{\"a}nde bilden sich durch Relaxierung der Oberfl{\"a}che: nach einigen Stunden im UHV, nach Heizen in Argon-Atmosph{\"a}re und nach Belegung mit Natrium. Die Charakterisierung dieser definierten Wolframoxid-Schichten erfolgt durch: 1.)XPS-Intensit{\"a}ten 2.)detailierte Analyse der W4f-Rumpfniveaus durch Synchrotronstrahlung (Bessy, TGM 7) 3.)die Variation der Austrittsarbeit beim Heizen und bei Natrium-Belegung 4.)das Auftreten von Gap-Zust{\"a}nden in der Bandl{\"u}cke}, language = {de} } @inproceedings{HoffmannMikaloSchmeisser, author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Schmeißer, Dieter}, title = {PEEM-Untersuchung an Spaltfl{\"a}chen von MoTe2-(0001)}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Molybd{\"a}nditellurid (MoTe2) geh{\"o}rt zu den Schichtgitterverbindung und ist im allgemeinen durch den Herstellungsprozeß n-dotiert. Proben dieses MoTe2 wurden im Ultrahochvakuum gespalten und die so erhaltenen sauberen (0001)-Spaltfl{\"a}chen mit einem Photoemissions-Elektronenmikroskop (PEEM) untersucht. Diese Untersuchung erbrachte nebeneinander auf den Proben- oberfl{\"a}chen liegende stark kontrastierte helle und dunkle Bereiche. Da das PEEM Austrittsarbeitsunterschiede als Kontrast darstellt, k{\"o}nnen diese hellen und dunklen Bereiche auf lokale Unterschiede in der Austrittsarbeit zur{\"u}ckgef{\"u}hrt werden. Weiterhin wird {\"u}ber den Versuch berichtet, eine Zuordnung zwischen dem Kontrast und dem Unterschied in der Austrittsarbeit mit Hilfe eines Elektronenenergie-Analysators (micro-ESCA) zu treffen.}, language = {de} } @misc{SowinskaDasWojciechowskietal., author = {Sowinska, Małgorzata and Das, Chittaranjan and Wojciechowski, Konrad and Rouissi, Zied and Snaith, Henry J. and Schmeißer, Dieter}, title = {Atomic layer deposition of Al2O3 on CH3NH3PbI3 for enhancement of perovskite solar cells stability}, series = {Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society}, volume = {15}, journal = {Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society}, number = {1-2}, issn = {1644-7190}, pages = {S. 33}, language = {en} } @misc{SchmeisserJanowitz, author = {Schmeißer, Dieter and Janowitz, Christoph}, title = {The Cu2p-edge of superconducting BiSrCu-Oxides studed by resonant Photoelectron Spectroscopy}, series = {Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society}, volume = {15}, journal = {Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society}, number = {1-2}, issn = {1644-7190}, pages = {S. 35}, language = {en} } @inproceedings{DasTallaridaSchmeisser, author = {Das, Chittaranjan and Tallarida, Massimo and Schmeißer, Dieter}, title = {TiO2 laminated Silicon microstructures based stable photocathode for water splitting}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, pages = {S. 213}, abstract = {The photoelectrochemical (PEC) water splitting is one of the most efficient ways to obtain hydrogen from water using solar power which can be used as carbon free fuel. The PEC device can bedesigned using semiconducting material that will convert solar radiation to H2. Silicon can be one of the best choices for PEC due to its success in solar cells technology. There are certain issues with Si such as stability in electrochemical medium [1] and higher surface reflectance (25\%) which limits the Si as an ideal candidate for PEC technique [2]. In the present work we addressed these issues by surface structuring and laminating the surface with metal oxide. The microstructuring of Si was done by electrochemical method. The Si microstructure photocathode was stabilized by thin layer of ALD grown TiO2 film. The microstructuring and lamination of Si photocathode by ALD layer of TiO2 decreased the reflectance ofthe surface and shift the onset potential towards anodic direction by 350 mV with a prolonged stability over 60 hours[3]. [1] C. Levy-Clement, J. Electrochem. Soc 1991, 12, 69 [2] J. Oh, et al. Energy Environ. Sci., 2011, 4, 1690 [3] C. Das, et al. Nanoscale 2015,7, 7726}, language = {en} }