TY - GEN A1 - Lewerenz, Hans-Joachim A1 - Aggour, Mohammed A1 - Murrell, Chris A1 - Kanis, M. A1 - Jungblut, H. A1 - Jakubowicz, J. A1 - Cox, P. A. A1 - Campbell, S. A. A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter T1 - Initial stages of structure formation on silicon electrodes investigated by photoelectron spectroscopy using synchrotron radiation and in-situ atomic force microscopy T2 - Journal of the Electrochemical Society N2 - The surface condition of electrochemically H-terminated Si is compared with the situation at the first photocurrent maximum in dilute acidic ammonium fluoride solution where the divalent dissolution converts into the four-valence process. The first high spectral-resolution photoelectron spectroscopy data using synchrotron radiation of electrochemically hydrogenated Si are presented. A combined electrochemistry/ultrahigh vacuum surface analysis system, attached to the U 49/2 beamline at the synchrotron Bessy II, is used for photoelectron spectroscopy (PES) of the electrochemically conditioned samples. We analyze the Si 2p, O 1s, and F 1s core levels. A comparison of a density functional theory calculation of the reaction sequence, proposed in the dissolution model of Gerischer and co-workers, with the PES results supports this model. The anodized sample is characterized by a residual H coverage of 0.35 monolayers evidenced by a surface core level shift, Si-OH and Si-Fx species, F-, and a higher oxidized Si species. SiO2 is not found. Even on very well H-terminated surfaces, we find residual Si-OH complexes, fluoride and water. In situ atomic force microscopy shows a roughening with a root mean square roughness parameter of 2.6 nm. %A92003 The Electrochemical Society. All rights reserved. Y1 - 2003 SN - 1945-7111 VL - 150 IS - 3 SP - E185 EP - E189 ER - TY - GEN A1 - Lewerenz, Hans-Joachim A1 - Murrell, Chris A1 - Jakubowicz, J. A1 - Aggour, Mohammed A1 - Kanis, M. A1 - Campbell, S. A. A1 - Cox, P. A. A1 - Hoffmann, Patrick A1 - Jungblut, H. A1 - Schmeißer, Dieter T1 - High Resolution Surface analysis of Si Roughenning in Dilute Ammonium Fluoride Solution T2 - Journal of Electroanalytical Chemistry N2 - The initial stages of porous Si formation on Si(111) in dilute ammonium fluoride solution are analysed by photoelectron spectroscopy using synchrotron radiation (SRPES). The PES results in the por-Si formation regime partly support a recent dissolution model. The contribution from the Si 2p surface core level shift shows that 0.35 ML of the surface is still H-terminated after interruption of the conditioning process at the first photocurrent maximum. Two signals shifted in binding energy by 0.8 and 1 eV, respectively, are attributed to reaction intermediates expected from the proposed reaction mechanism and from theoretical calculations using density functional theory (DFT). A distinct roughening is found in in-situ AFM measurements, with a calculated RMS roughness parameter of 2.6 nm. KW - Porous Si KW - transistors KW - Electropolishing KW - Photoelectron spectroscopy KW - AFM KW - Synchrotron radiation Y1 - 2003 SN - 1873-2569 VL - 540 SP - 3 EP - 6 ER - TY - GEN A1 - Lewerenz, Hans-Joachim A1 - Aggour, Mohammed A1 - Murrell, Chris A1 - Kanis, M. A1 - Hoffmann, Patrick A1 - Jungblut, H. A1 - Schmeißer, Dieter T1 - Interface engineering of photoelectrochemically prepared Si surfaces N2 - The oxide of Si(111) formed by electropolishing in dilute ammonium fluoride solution is analysed by photoelectron spectroscopy using synchrotron radiation. The oxidiclayer is about 3.1 nm thick and contains Si-F-x species as well as oxyfluorides. The oxyfluorides are found preferentially at the electropolishing layer surface. SiOHspecies are concentrated at the oxidic film/substrate interface. The full width half maximum of the Si 2p line indicates that the Si/electropolishing oxide interface issmoother than the Si/natural oxide interface. KW - Mean Free Paths KW - Silicon KW - Range Y1 - 2002 ER - 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 -