@article{MuellerHoffmannMilkoetal., author = {M{\"u}ller, Klaus and Hoffmann, Patrick and Milko, S. and Burkov, Yevgen and Schmeißer, Dieter}, title = {PEEM and µ-NEXAFS of Cu-In-S-Surfaces}, abstract = {The composition of CuInS2-films tends to differ from the ideal ratio of 1:1:2. A molecularlyvariation of dm=[Cu]/[In]-1 not equal 0 occurs due to the formation of binary phases as segregation's at the surface, as crystallites in the bulk of the film or at the surface of grains [1]. Furthermore, the range of homogeneity of the phase CuInS2 is relatively large caused by a low enthalpy of formation of defects like Cu-vacancies [2]. Segregation's at surfaces can be removed by KCN etching or by an electrochemical process [3, 4] We investigated the effect of an in-situ-heat-treatment of samples, prepared in the Cu-rich regime with additional amounts of copper, deposited on the surface of the Cu-In-S-films.We used Cu-In-S-films on molybdenum, prepared from precursors of Cu/In and a following reactive annealing-process in a sulphur-atmosphere. The experiments were performed as follows: The surface of the films was cleaned in situ to remove CuS-Phases by Argon-bombardment. The thin layers of additional Copper were prepared by evaporation of copper metal in Knudsen-cells. The thickness of this copper-films is in the range of monolayers, revealed by a calibration with copper on iron-substrates. After this deposition the samples were heated up to several temperatures (up to 550 ºC) for ten minutes, respectively. Here the molybdenum back-contact was used as electrical heater.}, language = {en} } @misc{MuellerBurkovSchmeisser, author = {M{\"u}ller, Klaus and Burkov, Yevgen and Schmeißer, Dieter}, title = {PEEM and my-NEXAFS of Cu-In-S2-surfaces}, series = {Thin Solid Films}, volume = {431-432}, journal = {Thin Solid Films}, issn = {0040-6090}, pages = {307 -- 311}, abstract = {Polycrystalline CuInS2 samples are an ideal system for photoemission electron microscope studies. The polycrystalline grains have a diameter of approximately 5 small mu, Greekm and the system is expected to be highly inhomogeneous because of the existence of many sub-phases. We used a recently established procedure to reproducibly obtain stoichiometric CuInS2-surfaces and follow the changes in the morphology, the elemental inhomogeneous distribution, and the development of the electronic structure upon its preparation. We find that the individual grains trend to coagulate, the surface composition becomes more homogeneous, and identify characteristic features of the unoccupied DOS.}, language = {en} } @misc{MuellerGoryachkoBurkovetal., author = {M{\"u}ller, Klaus and Goryachko, Andriy and Burkov, Yevgen and Schwiertz, Carola and Ratzke, Markus and K{\"o}ble, J. and Reif, J{\"u}rgen and Schmeißer, Dieter}, title = {Scanning Kelvin Probe Microscopy and Photoemission electron microscopy of organic source-drain structures}, series = {Synthetic Metals}, volume = {146}, journal = {Synthetic Metals}, number = {3}, issn = {0379-6779}, pages = {377 -- 382}, abstract = {n order to optimize organic field effect transistors (OFETs), the characterisation of active-layer surfaces in terms of their roughness, chemical composition and distribution of surface potentials is important. We report on high-resolution microscopic mapping of organic source-drain structures with P3HT as the semiconductor by scanning Kelvin probe microscopy (SKPM) and photoemission electron microscopy (PEEM). It was shown that PEEM is able to characterise the surface morphology (roughness), the chemical homogeneity and the composition of organic structures. The two-dimensional mapping of surface potentials by SKPM with applied source-drain voltages is shown to be an important ingredient of OFETs failure mode analysis.}, language = {en} } @article{MuellerScheerSchmeisseretal., author = {M{\"u}ller, Klaus and Scheer, R. and Schmeißer, Dieter and Burkov, Yevgen}, title = {Preparation of stoichiometric CuInS2-Surfaces}, series = {Thin Solid Films}, volume = {451-452}, journal = {Thin Solid Films}, issn = {0040-6090}, pages = {120 -- 123}, language = {en} } @article{MuellerBurkovSchmeisser, author = {M{\"u}ller, Klaus and Burkov, Yevgen and Schmeißer, Dieter}, title = {Photo-Emission-Electron-Microscopy for Characterization of an Operating Organic Electronic Device}, language = {en} } @incollection{MuellerBurkovMandaletal., author = {M{\"u}ller, Klaus and Burkov, Yevgen and Mandal, Dipankar and Henkel, Karsten and Paloumpa, Ioanna and Goryachko, Andriy and Schmeißer, Dieter}, title = {Microscopic and spectroscopic characterization of interfaces and dielectric layers for OFET devices}, series = {Organic Electronics : structural and Electronic Properties of OFETs}, booktitle = {Organic Electronics : structural and Electronic Properties of OFETs}, editor = {W{\"o}ll, Christof}, publisher = {Wiley-VCH}, address = {Weinheim}, isbn = {978-3-527-40810-8}, pages = {445 -- 468}, language = {en} } @inproceedings{MuellerMilkoBurkovetal., author = {M{\"u}ller, Klaus and Milko, Sergey and Burkov, Yevgen and Schmeißer, Dieter}, title = {Mischkristalle des Systems ZnS-CuInS2 f{\"u}r multispektrale Solarzellen}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Wir haben CuInS2 (CIS) unterschiedlicher Herstellung (Koverdampfung, Sputtern, Pulsed Laser Deposition, CIS auf Kupferband aufgebracht) untersucht. Neben Tiefenprofilen (durch Sputtern) der Elementverteilung dieser Proben wurden der Einfluss der Temperatur, von aufgedampftem Kupfer und Indium, ebenfalls bei verschiedenen Temperaturen, auf das Verhalten der St{\"o}chiometrie mit spektroskopischen Methoden (XPS, UPS) studiert. Parallel dazu wurde das Verhalten von im Vakuum aufgedampften ZnS und die entsprechenden Oberfl{\"a}chenreaktionen in Abh{\"a}ngigkeit von der Temperatur untersucht und charakterisiert, so dass Aussagen {\"u}ber die Optimierung und Anpassung von Pr{\"a}parationsbedingungen und Parametern zur Herstellung von erstens reinem CIS und zweitens von Mischkristallen des Typs Zn2-xCuxInxS2 m{\"o}glich werden. Zwischen den beiden Endgliedern ZnS und CuInS2 besteht bis auf einen Phasen{\"u}bergang bei etwa 80\% CIS l{\"u}ckenlose Mischbarkeit gem{\"a}ss Zn2-xCuxInxS2 (Bente: Chem.Erde (1991)). Die elektronische Bandl{\"u}cke dieser Mischkristalle l{\"a}sst sich im Vergleich zu reinem CuInS2 in einem Bereich von 3,67 eV (ZnS) bis 1,55 eV (CuInS2) variieren. Damit besteht die M{\"o}glichkeit, durch kontrollierte {\"A}nderung der Zusammensetzung der Schichten die Effizienz von Solarzellen aus diesem Material zu optimieren.}, language = {de} } @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{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} }