TY - GEN A1 - Aggour, Mohammed A1 - Stoerkel, Ulrich A1 - Murrell, Chris A1 - Campbell, S. A. A1 - Jungblut, H. A1 - Hoffmann, Patrick A1 - Mikalo, Ricardo Pablo A1 - Schmeißer, Dieter A1 - Lewerenz, Hans-Joachim T1 - Electrochemical interface modification of CuInS2 thin films N2 - We studied two novel electrochemical treatments of CuInS2 solar-cell absorber films, introduced to remove the deleterious segregated CuS phase. Their influence onsurface topography, chemistry and electronic properties was investigated using in situ atomic force microscopy (AFM) and photoclectron spectroscopy, performed inpart at the U49/2 undulator beam line at BESSY II. The results are examined in order to develop an improved understanding of the chemical-electrochemical surfacetransformation processes. KW - thin-film solar cells KW - copper indium disulfide KW - atomic force microscopy (AFM) KW - photoelectron spectroscopy KW - synchrotron radiation KW - Solar-Cell Y1 - 2002 ER - TY - JOUR A1 - Hoffmann, Patrick A1 - Mikalo, Ricardo Pablo A1 - Schmeißer, Dieter T1 - PEEM - a spectromicroscopic tool for mc-Si surface evaluation N2 - The photo emission electron microscope (PEEM) with its direct imaging of the sample surface is a convenient tool for fast evaluation of large sample areas. It is possibleto handle samples with a size of 30 mm x 30 mm.With PEEM it is possible to visualise grain boundaries and crystal displacements without removing the native oxide. No special sample treatment is needed exceptchemical polishing of the sample surface and a HF-dip to obtain a thin (1 ... 2 nm) oxide layer.The quality of that oxide was proofed by high resolution photo electron spectroscopy (PES) at a synchrotron. The results were compared to native oxide onsingle-crystalline Si and no suboxides (e.g. SiO) were found. Our spectromicroscopic PEEM measurements show no difference in the oxide qualities of different grainsand on grain boundaries or crystal displacements. Furthermore no difference in the binding energy of Si2p core levels were found.In addition to grain boundaries other spot-like features were found on the sample surface. These could be identified in some cases as precipitation of Ca underneath thenative oxide. KW - multicrystalline silicon KW - photoelectron spectroscopy KW - PEEM Y1 - 2002 ER - TY - CHAP A1 - Schmeißer, Dieter A1 - Hoffmann, Patrick A1 - Müssig, Hans-Joachim T1 - The Pr2O3/Si(001) interface: a mixed Si-Proxide T2 - BESSY annual report 2001 Y1 - 2002 SP - 171 EP - 173 PB - Bessy CY - Berlin ER - TY - JOUR A1 - Müller, Klaus A1 - Hoffmann, Patrick A1 - Milko, S. A1 - Burkov, Yevgen A1 - Schmeißer, Dieter T1 - PEEM and µ-NEXAFS of Cu-In-S-Surfaces N2 - 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. Y1 - 2002 ER - TY - CHAP A1 - Henkel, Karsten A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter T1 - Backpropagation-Netzwerke für ein Zweisensorsystem zur Erfassung von Kohlendioxidkonzentrationen und relativer Luftfeuchte T2 - Sensoren im Fokus neuer Anwendungen : Verbraucherschutz und Lebensmittelkontrolle, Biosysteme und Nanobiotechnologie, Umweltmesstechnik, neue Sensormaterialien, Mess- und Eichwesen N2 - Zwei Schwingquarzsensoren mit gleicher sensitiver Beschichtung wurden zur Messung von CO2-Konzentrationen bei variierenden Luftfeuchten genutzt. Die Daten wurden neuronalen Netzen mit unterschiedlicher Architektur trainiert. Zwei Netze wurden auf ihre Generalisierungsfähigkeit getestet und miteinander verglichen. Für ein einstufiges Netz konnten Ergebnisse mit Fehlern kleiner 12% für die CO2-Konzentration und kleiner 5% für die Luftfeuchte erzielt werden. Ein zweistufiges Netz erkannte Kategorien der Luftfeuchte 100%-ig, für die CO2-Konzentration wurden Fehler kleiner 9% erreicht, wobei eine deutlich bessere Generalisierungsfähigkeit dieses Netzes im Vergleich zum einstufigen Netz zu verzeichnen ist. Y1 - 2002 SN - 3-935712-71-5 SN - 978-3-935712-71-2 SP - 104 EP - 107 PB - w.e.b. Universitätsverlag CY - Dresden ER - TY - JOUR A1 - Batchelor, David R. A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter T1 - Photoemission study of Aluminium Steel cold welded joints N2 - Aluminium and Stainless Steel bi-metal material is extremely versatile and is used in a wide range of products; from cooking utensils to high technology applications such as automobile manufacture and Synchrotron radiation instrumentation. As a consequence of this wide range of applications the study of the formation of Aluminium Steel junctions and the bonding mechanism is of considerable industrialimportance [1-3].In a previous publication [4] evidence for a chemical bond, alloying at the interface was found. As the monochromator focus and welded region are similar in size about 200 µm (the actual interface from SEM is an order of magnitude smaller) a simple photoemission experiment of translating the sample perpendicular (vertically, weld horizontal) to the weld and measuring spectra was performed. Y1 - 2002 ER - TY - JOUR A1 - Jäckel, B. A1 - Thißen, A. A1 - Hunger, Ralf A1 - Klein, A. A1 - Jaegermann, Wolfram A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter T1 - Focus IS-PEEM investigations at U49/II: experimental determination of a magnification function, the contrast mechanism and the spectral resolution Y1 - 2002 ER - TY - JOUR A1 - Hoffmann, Patrick A1 - Mikalo, Ricardo Pablo A1 - Schmeißer, Dieter T1 - A spectro-microscopic approach for spatially resolved characterisation of semiconductor structures in PEEM Y1 - 2000 ER - TY - JOUR A1 - Mikalo, Ricardo Pablo A1 - Appel, Günter A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter T1 - Determination of the Vacuum Level in NEXAFS-spectra by Selected-Yield-NEXAFS Y1 - 1999 ER - TY - JOUR A1 - Hoffmann, Patrick A1 - Mikalo, Ricardo Pablo A1 - Schmeißer, Dieter T1 - Photoemissionselektronenmikroskopie - ein Instrument für die Materialforschung Y1 - 1999 ER - TY - CHAP A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter A1 - Engelmann, Hans-Jürgen A1 - Zschech, Ehrenfried A1 - Stegmann, Heiko A1 - Himpsel, Franz J. A1 - Denlinger, Jonathan D. ED - Tsui, Ting Y. T1 - Characterization of chemical bonding in low-k dielectric materials for interconnect isolation: A XAS and EELS Study T2 - Materials, technology and reliability of low-k dielectrics and copper interconnects, symposium held April 18 - 21, 2006, San Francisco, California Y1 - 2006 SN - 978-1-55899-870-5 SP - 55 EP - 62 PB - Materials Research Society CY - Warrendale, Pa. ER - TY - CHAP A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter A1 - Himpsel, Franz J. A1 - Engelmann, Hans-Jürgen A1 - Zschech, Ehrenfried A1 - Stegmann, Heiko A1 - Denlinger, Jonathan D. T1 - Characterization of Chemical Bonding in Low-K Dielectric Materials for Interconnect Isolation: XAS and EELS Study T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft ; Reihe 6, Bd. 41 N2 - 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. Y1 - 2006 SN - 0420-0195 SP - S. 156 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Schmeißer, Dieter A1 - Hoffmann, Patrick A1 - Beuckert, Guido ED - Zschech, Ehrenfried ED - Whelan, Caroline T1 - Electronic Properties of the Interface Formed by Pr2o3 Growth on Si(001), Si(111)and SiC(0001) Surfaces Y1 - 2005 ER - TY - CHAP A1 - Zschech, Ehrenfried A1 - Stegmann, Heiko A1 - Schmeißer, Dieter A1 - Hoffmann, Patrick T1 - Chemical Bonding, Permittivity, and Elastic Properties in Locally Modified Organosilicate Glass Y1 - 2006 ER -