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Title: Atomic structure and chemistry of Si/Ge interfaces determined by Z-contrast stem

Abstract

The technique of Z-contrast STEM provides a fundamentally new and powerful approach to determining the atomic scale structure and chemistry of interfaces. The images produced do not show contrast reversals with defocus or sample thickness, there are no Fresnel fringe effects at interfaces, and no contrast from within an amorphous phase. Such images are unambiguous and intuitively interpretable. In this paper, the technique has been used to directly image subnanometer interdiffusion in ultrathin (Si{sub m}Ge{sub n}){sub p} superlattices. The Z-contrast image of a (Si{sub 8}Ge{sub 2}){sub p} superlattice grown by MBE at 400{degree}C clearly shows significant broadening of the Ge-rich layer. Also, film formation and misfit accommodation in epitaxial Ge films on (001)Si produced by implantation and oxidation of Si wafers was studied. It was found that the Ge films, which are constrained to grow layer-by-layer, remain completely coherent with the Si substrate to thickness of 5--6 nm. This is 3 to 6 times thicker than the observed critical thickness for Ge films grown on Si by MBE. It is observed that misfit accommodating dislocations nucleate at the film surface as Shockley partials. The Z-contrast images show these partials can combine to form perfect dislocations whose cores are found tomore » lie entirely in the elastically softer Ge film. 8 refs., 5 figs.« less

Authors:
; ;
Publication Date:
Research Org.:
Oak Ridge National Lab., TN (USA)
Sponsoring Org.:
DOE/ER
OSTI Identifier:
5147184
Report Number(s):
CONF-891119-81
ON: DE90006150
DOE Contract Number:  
AC05-84OR21400
Resource Type:
Conference
Resource Relation:
Conference: Materials Research Society fall meeting, Boston, MA (USA), 27 Nov - 2 Dec 1989
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; INTERFACES; ELECTRON MICROSCOPY; SEMICONDUCTOR MATERIALS; CRYSTAL LATTICES; DISLOCATIONS; ELECTRONIC STRUCTURE; GERMANIUM; ION IMPLANTATION; OXIDATION; SILICON; THIN FILMS; CHEMICAL REACTIONS; CRYSTAL DEFECTS; CRYSTAL STRUCTURE; ELEMENTS; FILMS; LINE DEFECTS; MATERIALS; METALS; MICROSCOPY; SEMIMETALS; 360602* - Other Materials- Structure & Phase Studies; 400102 - Chemical & Spectral Procedures

Citation Formats

Chisholm, M F, Pennycook, S J, and Jesson, D E. Atomic structure and chemistry of Si/Ge interfaces determined by Z-contrast stem. United States: N. p., 1989. Web.
Chisholm, M F, Pennycook, S J, & Jesson, D E. Atomic structure and chemistry of Si/Ge interfaces determined by Z-contrast stem. United States.
Chisholm, M F, Pennycook, S J, and Jesson, D E. 1989. "Atomic structure and chemistry of Si/Ge interfaces determined by Z-contrast stem". United States.
@article{osti_5147184,
title = {Atomic structure and chemistry of Si/Ge interfaces determined by Z-contrast stem},
author = {Chisholm, M F and Pennycook, S J and Jesson, D E},
abstractNote = {The technique of Z-contrast STEM provides a fundamentally new and powerful approach to determining the atomic scale structure and chemistry of interfaces. The images produced do not show contrast reversals with defocus or sample thickness, there are no Fresnel fringe effects at interfaces, and no contrast from within an amorphous phase. Such images are unambiguous and intuitively interpretable. In this paper, the technique has been used to directly image subnanometer interdiffusion in ultrathin (Si{sub m}Ge{sub n}){sub p} superlattices. The Z-contrast image of a (Si{sub 8}Ge{sub 2}){sub p} superlattice grown by MBE at 400{degree}C clearly shows significant broadening of the Ge-rich layer. Also, film formation and misfit accommodation in epitaxial Ge films on (001)Si produced by implantation and oxidation of Si wafers was studied. It was found that the Ge films, which are constrained to grow layer-by-layer, remain completely coherent with the Si substrate to thickness of 5--6 nm. This is 3 to 6 times thicker than the observed critical thickness for Ge films grown on Si by MBE. It is observed that misfit accommodating dislocations nucleate at the film surface as Shockley partials. The Z-contrast images show these partials can combine to form perfect dislocations whose cores are found to lie entirely in the elastically softer Ge film. 8 refs., 5 figs.},
doi = {},
url = {https://www.osti.gov/biblio/5147184}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Dec 01 00:00:00 EST 1989},
month = {Fri Dec 01 00:00:00 EST 1989}
}

Conference:
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