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The interplay of surface morphology and strain relief in surfactant mediated growth of Ge on Si(111)
A278 Surface Science 284 (1993) 53-66 North-Holland
The interplay of surface morphology and strain relief in surfactant mediated growth of Ge on S i ( l l l ) M. Horn-von Hoegen, M. Pook, A. AI Falou, B.H. Miiller and M. Henzler lnstitut fiir Festki~rperphysik, Universitiit Hannover, Appetstrasse 2, 3000 Hannover 1, Germany Received 26 August 1992; accepted for publication 5 November 1992 The growth of Ge on Si is strongly modified by surface active species called surfactants. While the effectiveness of Sb as a surfactant in forcing layer-by-layer growth of Ge on Si(lll) and in creating a misfit adjusting dislocation network confined to the Si/Ge-interface has been demonstrated in previous studies, the dynamic growth process on an atomic scale leadingto this result is still unknown. The relevance of the stress on surface morphology and the growth mode of Ge on Si(111) is presented in a detailed in situ study by spot profile analysing low energy electron diffraction during the deposition. The change from islanding to layer-by-layer growth is seen in the oscillatory intensity variation of the (00)-spot. To relieve the strain the Ge-film forms a microscopically rough surface of small triangular and defect free pyramids in the pseudomorphic growth regime up to 8 monolayers. As soon as the pyramids are completed and start to coalesce, strain relieving defects are created at their base, finally arranging to the dislocation network. After the overgrowth of the dislocations the surface smoothes again showing a much larger terrace length. The periodic dislocation network at the interface gives rise to an elastic deformation of the surface, which results in a spot splitting in LEED. Thus, for the first time the dynamics of the formation of a dislocation network has been observed in situ during the growth process. Surprisingly, the dislocation network is already completed to 70% immediately after 8 monolayers of coverage, which is attributed to the micro-rough surface morphology, providing innumerous nucleation sites for dislocation.
Surface Science 284 (1993) 67-76 North-Holland
Medium energy ion scattering study of Ni on ultrathin films of SiO 2 on Si(111) J.B. Zhou, T. Gustafsson Department of Physics and Astronomy & Laboratory for Surface Modification, P.O. Box 849, Rutgers - The State University of New Jersey, Piscataway, NJ 08855-0849, USA
R.F. Lin and E. Garfunkel Department of Chemistry & Laboratory for Surface Modification, P.O. Box 939, Rutgers - The State University of New Jersey, Piscataway, NJ 08855-0939, USA Received 26 May 1992; accepted for publication 8 October 1992 The structure of thin Ni films ( ~ 7 ,~) deposited at room temperature on ultrathin SiO 2 layers on Si(lll) has been studied using medium energy ion scattering. Our results indicate that the Ni films deposited at room temperature are not uniform, The data have been fitted with two model approximations, In one, the overlaycr structures are characterized by spherical:caps with a radius of 39 and height of 22 A, while in the second they are characterized by a thickness distribution function with an average thickness of 14 and deviation of 7 .~. Above 750 K, Ni atoms start to diffuse through the SiO 2 layer and subsequently into the near-surface region of the crystalline Si substrate. After annealing to 1075 K, some of the Ni has diffused into the substrate to a depth of at least 800 ~k. In this final state, the SiO 2 is completely desorbed and nickel silicides are formed.
The interplay of surface morphology and strain relief in surfactant mediated growth of Ge on S i ( l l l ) M. Horn-von Hoegen, M. Pook, A. AI Falou, B.H. Miiller and M. Henzler lnstitut fiir Festki~rperphysik, Universitiit Hannover, Appetstrasse 2, 3000 Hannover 1, Germany Received 26 August 1992; accepted for publication 5 November 1992 The growth of Ge on Si is strongly modified by surface active species called surfactants. While the effectiveness of Sb as a surfactant in forcing layer-by-layer growth of Ge on Si(lll) and in creating a misfit adjusting dislocation network confined to the Si/Ge-interface has been demonstrated in previous studies, the dynamic growth process on an atomic scale leadingto this result is still unknown. The relevance of the stress on surface morphology and the growth mode of Ge on Si(111) is presented in a detailed in situ study by spot profile analysing low energy electron diffraction during the deposition. The change from islanding to layer-by-layer growth is seen in the oscillatory intensity variation of the (00)-spot. To relieve the strain the Ge-film forms a microscopically rough surface of small triangular and defect free pyramids in the pseudomorphic growth regime up to 8 monolayers. As soon as the pyramids are completed and start to coalesce, strain relieving defects are created at their base, finally arranging to the dislocation network. After the overgrowth of the dislocations the surface smoothes again showing a much larger terrace length. The periodic dislocation network at the interface gives rise to an elastic deformation of the surface, which results in a spot splitting in LEED. Thus, for the first time the dynamics of the formation of a dislocation network has been observed in situ during the growth process. Surprisingly, the dislocation network is already completed to 70% immediately after 8 monolayers of coverage, which is attributed to the micro-rough surface morphology, providing innumerous nucleation sites for dislocation.
Surface Science 284 (1993) 67-76 North-Holland
Medium energy ion scattering study of Ni on ultrathin films of SiO 2 on Si(111) J.B. Zhou, T. Gustafsson Department of Physics and Astronomy & Laboratory for Surface Modification, P.O. Box 849, Rutgers - The State University of New Jersey, Piscataway, NJ 08855-0849, USA
R.F. Lin and E. Garfunkel Department of Chemistry & Laboratory for Surface Modification, P.O. Box 939, Rutgers - The State University of New Jersey, Piscataway, NJ 08855-0939, USA Received 26 May 1992; accepted for publication 8 October 1992 The structure of thin Ni films ( ~ 7 ,~) deposited at room temperature on ultrathin SiO 2 layers on Si(lll) has been studied using medium energy ion scattering. Our results indicate that the Ni films deposited at room temperature are not uniform, The data have been fitted with two model approximations, In one, the overlaycr structures are characterized by spherical:caps with a radius of 39 and height of 22 A, while in the second they are characterized by a thickness distribution function with an average thickness of 14 and deviation of 7 .~. Above 750 K, Ni atoms start to diffuse through the SiO 2 layer and subsequently into the near-surface region of the crystalline Si substrate. After annealing to 1075 K, some of the Ni has diffused into the substrate to a depth of at least 800 ~k. In this final state, the SiO 2 is completely desorbed and nickel silicides are formed.