The formation of hexagonal silicon at twin intersections

Journal Article · Wed Feb 01 04:00:00 EST 1989 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(89)90424-9· OSTI ID:6108572

Dahmen, U; Hetherington, C J; Westmacott, K H; Pirouz, P

The geometric configuration of intersecting twin bands has been considered in the past in the context of dislocation mechanisms and deformation behavior. It is generally found that a twin band is an effective barrier to the propagation of another, noncoplanar, twin band. However, under conditions of sufficiently high local stress twin intersections are possible, subject to conditions of continuity. The problem of intersecting twins has gained renewed interest with the recent hot-indention experiments in silicon. The deformation microstructure consists of twin bands and planar ribbons of hexagonal Si radiating from the area of the indent. Although at high pressures silicon forms in several different crystal structures, only the diamond-cubic structure is stable at atmospheric pressure. Thus the diamond-hexagonal structure that forms during hot indentation of single crystals is a metastable modification. Recent research established its crystallography by means of high-resolution electron microscopy. In particular, it was shown that the transformation from the diamond-cubic to the diamond-hexagonal structure was of a martensitic nature. It has been postulated that the formation of hexagonal Si in the deformation zone is related to multiple twinning, and a detailed crystallographic model for this transformation has been proposed. The present note reports such an observation by high resolution electron microscopy.

• Research Organization: Materials and Chemical Sciences Div., Lawrence Berkeley Lab., Berkeley, CA (US); Dept. of Materials Science and Engineering, Case Western Reserve Univ., Cleveland, OH (US)
• OSTI ID: 6108572
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 23:2; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
360602* -- Other Materials-- Structure & Phase Studies
ACTIVATION ENERGY
ALLOYS
AUSTENITIC STEELS
CARBON ADDITIONS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
DATA ANALYSIS
DEFORMATION
DIFFRACTION
ELECTRON MICROSCOPY
ELEMENTS
ENERGY
GEOMETRY
HEXAGONAL LATTICES
HYDROGEN
IRON ALLOYS
IRON BASE ALLOYS
MARTENSITE
MATHEMATICS
MICROSCOPY
MICROSTRUCTURE
NONMETALS
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
SCATTERING
SEMIMETALS
SILICON
STEELS
TEMPERATURE DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION