Strain relaxation of Si/Ge multilayers: Coherent islands formation and their evolution as a function of the strain
作者:
E. Carlino,
C. Giannini,
C. Gerardi,
L. Tapfer,
K. A. Ma¨der,
H. von Ka¨nel,
期刊:
Journal of Applied Physics
(AIP Available online 1996)
卷期:
Volume 79,
issue 3
页码: 1441-1447
ISSN:0021-8979
年代: 1996
DOI:10.1063/1.360982
出版商: AIP
数据来源: AIP
摘要:
We report on a structural study of Si/Ge multilayers grown by molecular‐beam epitaxy on (100)‐Si substrates. The analyses have been performed by using transmission electron microscopy, high‐resolution x‐ray diffraction, and secondary‐ion‐mass spectrometry. The investigated specimens differ in number of periods, period thickness, and in the Si/Ge periods thickness ratio. In particular, we investigate the interdiffusion of the Ge atoms in each superlattice period of the epilayer and in the epilayer as whole. The interdiffusion causes a broadening of the nominal thickness of the Ge layer producing a SixGe1−xalloy. Furthermore, the Ge content in the multilayer periods increases as a function of the growth time, i.e., the superlattice periods close to the sample surface contain more Ge atoms if compared to the periods close to the substrate/superlattice interface. We find two steps in the strain relaxation: (i) In each period the strain energy density is partially reduced by the formation of coherent islands; (ii) at a certain value of the strain energy density the shape of the islands changes and the structures relax partially or completely the accumulated strain energy by nucleation of extended defects. ©1996 American Institute of Physics.
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