TY - CHAP A1 - Tallarida, Massimo A1 - Karavaev, Konstantin A1 - Kolanek, Krzysztof A1 - Schmeißer, Dieter T1 - In-situ experimental approach to the study of atomic layer deposition with atomic force microscope, X-ray photoelectron and X-ray absorption spectroscopy T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 44 N2 - We describe our experimental approach to the investigation of atomic layer deposition (ALD). ALD is a powerful deposition technique for growing conformal thin films of composite materials with atomically accurate thickness on large area [1]. Despite the enormous industrial interest growing around ALD, its fundamental properties were not yet properly studied. We developed an ALD reactor for the in-situ investigations using XPS, XAS and AFM as experimental techniques. We studied the chemical-physical properties of the growing thin films after each deposition cycle. Here, we illustrate the recent results concerning the ALD of HfO2 obtained using different Hf-precursors on various substrates [2]. We show how the in-situ investigations could deliver an important insight into the fundamental characteristics of ALD and how these information could be used to modify and optimize the deposition parameters. [1] M. Leskelä, M. Ritala, Thin Solid Films, 409, 138, 2002; [2] M. Tallarida, K. Karavaev, and D. Schmeisser, J. Appl. Phys. 104, 064116 (2008). Y1 - 2009 UR - http://www.dpg-verhandlungen.de/year/2009/conference/dresden/part/ds/session/26/contribution/15 SN - 0420-0195 SP - S.176 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Seifarth, Olaf A1 - Walczyk, Christian A1 - Lupina, Grzegorz A1 - Zaumseil, Peter A1 - Schmeißer, Dieter A1 - Müssig, Hans-Joachim A1 - Schroeder, Thomas T1 - The electronic band diagram of thin PrO2(111) / Pr-silicate buffers on Si(111) and its relevance to dielectric properties T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 44 N2 - Thin dielectric buffers of cubic PrO2(111) on Si(111) are ideally suited to integrate Ge onto Si by moderating the lattice mismatch between the materials. The leakage current across this dielectric buffer is strongly influenced by the electronic band diagram and defects inside the band gap. Therefore, we measured the band offsets, band gaps and defect positions by means of synchrotron radiation based photoemission spectroscopy techniques (XPS and XAS) with special emphasis on the Pr-silicate interface. In a next step we compare the spectroscopic data with information from dielectric studies, based on temperature dependent leakage current studies. We observe a close relation between dielectric properties and the electronic structure. Y1 - 2009 UR - http://www.dpg-verhandlungen.de/year/2009/conference/dresden/part/df/session/6/contribution/5 SN - 0420-0195 SP - S. 136 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Friedrich, Daniel A1 - Michling, Marcel A1 - Schmeißer, Dieter A1 - Koval, Yuri A1 - Müller, Paul T1 - Characterization of ion beam modified polyimide layers T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45 N2 - Ion beam modified polyimide show high conductivity. In our investigation we focus on the electronic structure and the element composition, in order to understand the mechanism of conductivity. In our experiments we use the methods NEXAFS and PES. The measurements were done at the U49/2-PGM2 beam line of BESSY II, Berlin. We find an increase of the sp2 hybridized graphite contribution, after low Ar+ ion doses bombardment while the temperature of the samples is varied from 300 K to 650 K. In addition we follow the He+ bombardment induced changes by in-situ monitoring of the O1s, N1s content in the polyimide films. Y1 - 2010 UR - http://www.dpg-verhandlungen.de/year/2010/conference/regensburg/part/ds/session/38/contribution/10 SN - 0420-0195 SP - S. 247 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Dudek, Peter A1 - Lupina, Grzegorz A1 - Kozłowski, Grzegorz A1 - Dabrowski, Jarek Marek A1 - Lippert, Gunther A1 - Müssig, Hans-Joachim A1 - Schmeißer, Dieter A1 - Schroeder, Thomas T1 - Band structure and electrical properties of MBE grown HfO2 - based alkaline earth perovskites T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45 N2 - Ultra thin dielectric films (<20 nm) deposited on TiN electrodes are interesting for MIM capacitor application. High capacitance density and dielectric permittivity must be accompanied by extremely low leakage currents (10−8 A/cm2) at bias 0.5 V. To achieve such low leakage currents, high band gap and proper band alignment is required. Occupied electronic states can be probed with standard laboratory photoemission methods. Probing of unoccupied states is more challenging. Synchrotron based PES in combination with XAS forms a powerful method to study the band alignment. ASAM end station located at the U 49/2 PGM 2 beamline of BESSY II (Berlin) offers excellent conditions for performing such measurements. We investigated HfO2 - based alkaline earth perovskite - BaHfO3 with subsequent admixture of TiO2, resulting in formation of BaHf0.5Ti0.5O3 compound. The analysis of data indicates that band gap for HfO2 is similar to BaHfO3 and amounts 5.8 eV; for BaHf0.5Ti0.5O3 it decreases to 3.8 eV. We conclude that the addition of TiO2 to BaHfO3 increases significantly the dielectric permittivity but also impacts the band gap alignment. The conduction band offset shrinks, influencing the leakage current behavior. Y1 - 2010 UR - http://www.dpg-verhandlungen.de/year/2010/conference/regensburg/part/ds/session/24/contribution/4 SN - 0420-0195 SP - S. 232 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Friedrich, Daniel A1 - Koval, Yuri A1 - Müller, Paul A1 - Schmeißer, Dieter T1 - Electronic structure of thin spin-coated polyimide layers T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 46 N2 - The conductivity of polyimide layers can be modified by several orders of magnitude by ion beam radiation. In order to understand the electronic structure of the pure polyimide before ion beam modification we focus in our preliminary experiments on spectroscopic investigations of thin as prepared polyimide films. The films were made by spin coating from a PMDA/ODA solution with subsequent vacuum annealing at 350°C. The layer thickness can be controlled by changing the concentration of PMDA/ODA in the solution realizing a thickness down to 3.5nm. For the characterization of the as prepared thin polyimide films the techniques NEXAFS, ResPES, XPS and CIS were applied at the U49/2-PGM2 beam line of Bessy II, Berlin. Our data including the valence band, core levels and absorption spectrum were compared with theoretical LCAO calculations. Based on these results we are able to attribute all spectral features to the specific atomic bonds in the molecule. Y1 - 2011 UR - http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/ds/session/63/contribution/3 SN - 0420-0195 SP - S. 311 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Hoffmannbeck, David A1 - Richter, Matthias A1 - Städter, Matthias A1 - Paloumpa, Ioanna A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Spectroscopic and microscopic characterization of potential catalysts for the hydrogenation of CO2 T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 46 N2 - The reduction of CO2 emissions is a general demand of the society in order to avoid irreversible climate changes. We are investigating potential catalysts for the hydrogenation of CO2 in particular for its application in the so called oxyfuel combustion process. In order to understand the catalytic behavior of the investigated materials we use the techniques X-Ray Photoemission (XPS) and -absorption (XAS) Spectroscopy as well as X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The prospective of our work is to figure out the electronic and structural properties of the material and to optimize proper catalysts or design new ones for best catalytic activity. Beside the spectro-microscopic investigations the catalysts are tested under Sabatier reaction conditions in terms of activity, stability and sensitivity against poisoning. In our preliminary work we constructed a Sabatier reactor system with analytical parts based on infrared absorption and mass spectroscopy modules. First spectroscopic and catalytic results achieved on a commercially available Ru/Al2O3 catalyst will be presented. Y1 - 2011 UR - http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/o/session/60/contribution/123 SN - 0420-0195 SP - S. 483 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Kraatz, Matthias A1 - Zhang, Lijuan A1 - Schmeißer, Dieter A1 - Zschech, Ehrenfried A1 - Ho, Paul S. T1 - Statistical Analysis of Computer-simulated On-Chip Interconnect Electromigration Lifetimes under the Influence of Microstructure and Strengthened Top Interface T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 46 N2 - We are investigating the statistics of computer-simulated interconnect electromigration (EM) lifetimes with regard to the effects of microstructure and a strengthened top interface. The degradation process of EM once threatened the entire existence of integrated circuit industry in the 1960s and has remained a major reliability concern. Ongoing miniaturization and the introduction of new materials further complicate the task of EM-resistant chip manufacturing. We have developed a simple two-dimensional finite difference simulation that models the mass transport by electromigration along the grain boundaries and the top interface of interconnect segments that allows us to do calculations of void nucleation and growth. A parallel computer simulates hundreds of interconnects simultaneously and statistical analysis becomes feasible. A Monte Carlo grain growth algorithm (a modified Potts version) is applied to model the grain structure of the interconnect segments. We will show that the simulation can be used to compare simulation and experiment qualitatively. Four cases have been studied: interconnect segments with small/large grains and weak/strong top interface. Y1 - 2011 UR - http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/ds/session/7/contribution/2 SN - 0420-0195 SP - S. 292 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Mbua, Roy A1 - Müller, Klaus A1 - Richter, Matthias A1 - Henkel, Karsten A1 - Paloumpa, Ioanna A1 - Schmeißer, Dieter A1 - Kramm, Ulricke T1 - Investigation of new Catalysts for PEM Fuel Cells T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 46 N2 - Increasing green house emissions amplify global warming concerns worldwide. Fuel cells, based on polymer electrolyte membranes (PEM) are part of the solution to this issue. We aim at developing and testing new catalysts for fuel cells. Platinum catalysts perform best in PEM fuel cells to date but they are very expensive. For fuel cells to be perfectly applicable and economically affordable, an alternative catalyst with similar or even greater efficiency should be developed. Metal phthalocyanines are known to be good oxygen reduction catalysts and are associated with high electron transfer properties. We investigated Cobalt Phthalocyanine in its pure state mixed with Carbon Black (CoPc:Carbon Black=1:9) untreated and also after a treatment in N2 at several temperatures, up to 1000°C for 30 minutes. Results of XPS and EDX analyses reveal that the treatment at higher temperatures causes a rearrangement in the chemical states of Co, N and C atoms. Furthermore, results of cycling voltammetry (CV) analysis reveal that CoPc treated in N2 at 800°C exhibited a higher current density, in conclusion, a higher catalytic activity than the untreated CoPc. Y1 - 2011 UR - http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/o/session/60/contribution/119 SN - 0420-0195 SP - S. 483 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Michling, Marcel A1 - Kolanek, Krzysztof A1 - Schmeißer, Dieter A1 - Tallarida, Massimo T1 - A growth model for the HfO2 ALD process T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 46 N2 - In this contribution we report on our in-situ2 cycle-by-cycle (up to the 25 cycles) investigation of the HfO2 atomic layer deposition (ALD) process using the method of x-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). We used Tetrakis-Dimethyl-Amino-Hafnium (TDMA-Hf) and H2O as precursors and p-type Si wafer with native oxide as a substrate. The XPS measurements were carried out at BESSY II in Berlin with primary energies of 150 eV and 640 eV and the EELS measurements were done with a primary energy of 50 eV. We measured the O1s, Si2p core level and the valence band including the Hf 4f core level. From the Hf4f to Si2p ratios taken at each energy we developed a growth model for the first monolayer and for the following layers too. From our data we conclude, that in the first monolayer up to the fourth ALD cycle an island growth occurs. The height of these islands is about 0,5nm. After the first monolayer is completed, a layer- by-layer growth can be expected. In order to proof this observation we have simulated the Hf/Si ratio for different excitation energies and found a very good agreement with our measurement data. The EELS data especially the evaluation of the loss function onset confirm our growth model. Y1 - 2011 UR - http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/ds/session/12/contribution/1 SN - 0420-0195 SP - S. 294 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Philip, Shine A1 - Martinez, Elias A1 - Müller, Klaus A1 - Kunst, Marinus A1 - Schmeißer, Dieter T1 - Time resolved microwave conductivity measurements of Bulk Heterojunction solar cells T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 46 N2 - The time resolved microwave conductivity (TRMC) method was used in order to study the generation and decay kinetics of charge carriers in the Bulk Heterojunction (BHJ) solar cells. The charge carriers were generated with 532nm laser pulses of 10ns FWHM (Full Width at Half Maximum) induced in the cells. The BHJ solar cells used for the measurements had a photoactive layer consisting of a mixture of Poly (3-Hexylthiophene) P3HT and Phenyl-C61-butyric acid methyl ester (PCBM) which was spin coated onto Indium tin oxide (ITO)/glass substrates. In the field of Organic photovoltaic blends, TRMC method is introduced as a new method of direct investigation of the charge carrier lifetime as well as the charge carrier mobility and we were successful in studying the charge carrier lifetime of the reference BHJ solar cells. We also studied the influence of aligned ferroelectric fields on the charge separation in BHJ solar cells. As ferroelectric material, we used the copolymer Poly (vinylidene fluoride - trifluoroethylene) P(VDF-TrFE). Y1 - 2011 UR - http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/ds/session/42/contribution/31 SN - 0420-0195 SP - S. 301 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Richter, Matthias A1 - Schmeißer, Dieter T1 - Electronic structure and optical properties of P3HT - Evidence of 2D-polarons in P3HT T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 46 N2 - In this contribution we report on investigations of the electronic structure and optical characteristics of poly(3-hexylthiophene) (P3HT) based films. Various techniques like NEXAFS, SRXPS, UPS, UV-VIS and FTIR were used. X-Ray based measurements were done at the U49/2-PGM2 beam line at BESSYII. The samples were produced by spin casting P3HT dissolved in chloroform and other suitable solvents on ITO (indium tin oxide) coated glass slides and silicon substrates. Regioregular-P3HT is known to form thin films with nanocrystalline lamellae. This 2D structure give rise to additional electronic excitations in photoinduced absorption measurements, which are attributed to 2D-polarons [1]. In the Total Electron Yield (surface sensitive) and Total Fluorescence Yield (bulk sensitive) NEXAFS spectra of regioregular-P3HT three additional features can be found prior to the first typical π* excitation. The nature of these features was further investigated by means of SRXPS and UPS measurements. Energy differences relative to π*-peak maximum (0.54eV, 0.87eV and 2.24eV) suggest that these features are due to 2D-polarons. This presence of polarons is further confirmed by our FTIR and UV-VIS results. [1] Osterbacka et al., Synth. Met. 116 (2001) 317 Y1 - 2011 UR - http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/ds/session/64/contribution/3 SN - 0420-0195 SP - S. 311 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Schmidt, Stefan A1 - Schmeißer, Dieter T1 - Localized gap states in cobalt/nickel mixed oxides T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 46 N2 - Replacing Co by large amounts of Ni is considered to reduce costs in Li-Ion-Batteries while maintaining their performance. We investigate the electronic structure of Co/Ni compounds because of their direct impact on battery operation. Thin Co/Ni oxide films on metal substrates were prepared by dropping/spin-coating from nitrate solutions followed by subsequent annealing in air and UHV. The following Co to Ni ratios have been investigated: 50/50, 40/60, 30/70, and 20/80. The results are compared with the pure Co-oxide and magnetron sputtered LiCoO2 reference samples. Spectroscopic measurements on these samples were carried out at the U49/2 beamline at BESSYII, Berlin. XPS of the transition metal (TM) 2p states reveals the existence of charge transfer ground states and different oxidation states. NEXAFS at the Co L3, Ni L3 and O K edges reflects the density of unoccupied states while resonant PES at these edges provides the related partial density of states (pDOS). Therefore, these techniques can be used in order to distinguish between the different contributions of TM3d and O2p states in the valence band region. We find sharp localized features at the valence band edge and at the O K and Co L3 absorption edges that are discussed to originate from the strong hybridization between metal and oxygen states in that region. Y1 - 2011 UR - http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/o/session/69/contribution/2 SN - 0420-0195 SP - S. 486 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER -