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Monte Carlo simulations of Ge segregation in strained Si and SiGe alloys
A565 Surface Science 291 (1993) 110-116 North-Holland
The Ge Stranski-Krastanov growth mode on Si(001)(2 × 1) tested by X-ray photoelectron and Auger electron diffraction M. Diani, D. Aubel, J.L. Bischoff, L. Kubler and D. Bolmont Facult~ des Sciences et Techniques, Universit~ de Haute Alsace, LPSE, URA-CNRS 1435, 4, rue des Fr~res Lumi~re, 68093 Mulhouse Cedex, France Received 19 October 1992; accepted for publication 3 March 1993 X-ray photoelectron and Auger electron diffractions have been used here for the first time to identify growth morphology in the earliest stages (0-10 monolayers) of Ge epitaxy on Si(001)(2 × 1) surfaces held at room temperature (RT) and at 400°C. The Ge atomic arrangement in the (110) plane is examined by performing polar angle distribution of the Ge LMM intensities and by comparison with the corresponding Si2p substrate pattern. A detailed plot as a function of the Ge coverage of the forward scattering peak contrasts in the [111] and [001] directions, which correspond to the 1st and 3rd atomic neighbour rows, respectively, yields informations about the layer number distribution and the growth mode. Contrarily to the nearly two-dimensional (2D) growth taking place at RT, we obtain a 3D island formation at 400°C for a critical thickness exceeding 5 ML. Nevertheless, in the coverage domain between 2 and 5 ML for which layer-by-layer growth is normally expected, the observation of a significant up to 4 ML roughness across the surface prefigurates the islanding process and confirms very recent STM reports. Photoelectron scattering results are only consistent with pure 2D formation during the first 2 ML growth.
Surface Science 291 (1993) 117-128 North-Holland
Monte Carlo simulations of Ge segregation in strained Si and SiGe alloys Mats I. Larsson * and G6ran V. Hansson Department of Physics, Link6ping Institute of Technology, S-581 83 Link6ping, Sweden Received 19 October 1992; accepted for publication 26 February 1993 A simple Monte Carlo simulation model has been developed to study the segregation of Ge in strained Si and Sil_xGe x structures. The model is fitted to experimental SIMS data on the low concentration exponential surface segregation and the high concentration self-limited surface segregation at 450 and 560°C. The model treats the surface segregation as due to a thermally activated exchange process either during the adatom diffusion or after the capture of the adatom at a step. The simulated build-up of the Ge surface concentration at the growth of Si0.9Ge0.1 agrees well with experimental data. The simulations show that the surface segregation is negligible at 350°C and has a maximum at ~ 470"C. Growth simulations of ultrathin superlattices at 450"C show strongly broadened interfaces in the Ge bulk concentration profiles.
Surface Science 291 (1993) 129-138 North-Holland
Surface segregation of Pd-Ag membranes upon hydrogen permeation J. Shu, B.E.W. Bongondo, B.P.A. Grandjean, A. Adnot and S. Kaliaguine Department of Chemical Engineering and CERPIC, Laval University, Ste-Foy, Quebec, Canada G1K 7P4 Received 25 November 1992; accepted for publication 11 February 1993. Pd-Ag membranes are permeable to hydrogen. Hydrogen treatment results in a small chemical shift ( + 0.1-0.2 eV) of Pd 3d core level but no change in the Ag3d level. A new valence band in the binding energy region of 7-9 eV corresponding to the interaction between H ls and Pd 4d appears on a hydrogen permeated membrane surface. Quantitative XPS analysis reveals that Pd segregates at the membrane surface toward the high hydrogen pressure side while Ag segregation occurs at the surface on the low hydrogen pressure side after hydrogen permeation. Both surface segregations are explained based on an MTCIP-1A (modern thermodynamic calculation of interface properties - first approximation) approach. It is concluded that hydrogen chemisorption induces palladium segregation on the P d - A g membrane surface.
The Ge Stranski-Krastanov growth mode on Si(001)(2 × 1) tested by X-ray photoelectron and Auger electron diffraction M. Diani, D. Aubel, J.L. Bischoff, L. Kubler and D. Bolmont Facult~ des Sciences et Techniques, Universit~ de Haute Alsace, LPSE, URA-CNRS 1435, 4, rue des Fr~res Lumi~re, 68093 Mulhouse Cedex, France Received 19 October 1992; accepted for publication 3 March 1993 X-ray photoelectron and Auger electron diffractions have been used here for the first time to identify growth morphology in the earliest stages (0-10 monolayers) of Ge epitaxy on Si(001)(2 × 1) surfaces held at room temperature (RT) and at 400°C. The Ge atomic arrangement in the (110) plane is examined by performing polar angle distribution of the Ge LMM intensities and by comparison with the corresponding Si2p substrate pattern. A detailed plot as a function of the Ge coverage of the forward scattering peak contrasts in the [111] and [001] directions, which correspond to the 1st and 3rd atomic neighbour rows, respectively, yields informations about the layer number distribution and the growth mode. Contrarily to the nearly two-dimensional (2D) growth taking place at RT, we obtain a 3D island formation at 400°C for a critical thickness exceeding 5 ML. Nevertheless, in the coverage domain between 2 and 5 ML for which layer-by-layer growth is normally expected, the observation of a significant up to 4 ML roughness across the surface prefigurates the islanding process and confirms very recent STM reports. Photoelectron scattering results are only consistent with pure 2D formation during the first 2 ML growth.
Surface Science 291 (1993) 117-128 North-Holland
Monte Carlo simulations of Ge segregation in strained Si and SiGe alloys Mats I. Larsson * and G6ran V. Hansson Department of Physics, Link6ping Institute of Technology, S-581 83 Link6ping, Sweden Received 19 October 1992; accepted for publication 26 February 1993 A simple Monte Carlo simulation model has been developed to study the segregation of Ge in strained Si and Sil_xGe x structures. The model is fitted to experimental SIMS data on the low concentration exponential surface segregation and the high concentration self-limited surface segregation at 450 and 560°C. The model treats the surface segregation as due to a thermally activated exchange process either during the adatom diffusion or after the capture of the adatom at a step. The simulated build-up of the Ge surface concentration at the growth of Si0.9Ge0.1 agrees well with experimental data. The simulations show that the surface segregation is negligible at 350°C and has a maximum at ~ 470"C. Growth simulations of ultrathin superlattices at 450"C show strongly broadened interfaces in the Ge bulk concentration profiles.
Surface Science 291 (1993) 129-138 North-Holland
Surface segregation of Pd-Ag membranes upon hydrogen permeation J. Shu, B.E.W. Bongondo, B.P.A. Grandjean, A. Adnot and S. Kaliaguine Department of Chemical Engineering and CERPIC, Laval University, Ste-Foy, Quebec, Canada G1K 7P4 Received 25 November 1992; accepted for publication 11 February 1993. Pd-Ag membranes are permeable to hydrogen. Hydrogen treatment results in a small chemical shift ( + 0.1-0.2 eV) of Pd 3d core level but no change in the Ag3d level. A new valence band in the binding energy region of 7-9 eV corresponding to the interaction between H ls and Pd 4d appears on a hydrogen permeated membrane surface. Quantitative XPS analysis reveals that Pd segregates at the membrane surface toward the high hydrogen pressure side while Ag segregation occurs at the surface on the low hydrogen pressure side after hydrogen permeation. Both surface segregations are explained based on an MTCIP-1A (modern thermodynamic calculation of interface properties - first approximation) approach. It is concluded that hydrogen chemisorption induces palladium segregation on the P d - A g membrane surface.