Atomic structure and chemistry of Si/Ge interfaces determined by Z-contrast stem
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.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5147184
- Report Number(s):
- CONF-891119-81; ON: DE90006150
- Resource Relation:
- Conference: Materials Research Society fall meeting, Boston, MA (USA), 27 Nov - 2 Dec 1989
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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