Microcleavage, bonding character and surface structure in materials with tetrahedral coordination

Abstract

The investigation of mierocleavage, defined as the separation of crystals parallel to certain crystallographic directions, proves useful for detecting atomic arrays held together by strong bonds (PBC vectors). Estimates of ionic and covalent bonding character can be made and surface properties can be investigated.A structural collapse of the crystal surface layers in some materials with a low coordination

Fracture strength of micro- and nano-scale silicon components

“…Experimental evidence in support of this view of the formation of fracture surfaces in Si and the associated fracture energy calculation comes from a diversity of physical sources and includes direct transmission electron microscopy (TEM) observations of cracks by Lawn et al, showing sharp tips and negligible deformation of the body material and crack faces; 18 electron paramagnetic resonance signals associated with localized electron states (the dangling bonds) that increase in proportion to crack area for fractured Si; 19 electrical measurements showing that resistivity across cracks can reduce to zero as crack faces heal, in strong support of negligible fracture surface reconstruction; 20 mechanical grinding 16 and chemical etching 21 of Si spheres showing distinct tendencies to form surfaces in the order (111), (110), and (100), consistent with the above surface energy calculations; and a clear linear variation of (111) surface energies calculated as above with (brittle) semiconductor band gaps. 22 Supporting evidence from fracture modeling studies includes molecular statics calculations of (111) fracture in Si showing the dominance of the linear elastic continuum description for the crack-tip displacement field except for a very small (three atom) zone adjacent to the tip 23 and more recent molecular dynamics calculations 24,25 for fracture surfaces in [100], [110], and [111] zones showing excellent qualitative agreement with the variations of surface energy as in Fig.…”

InP Layer Transfer with Masked Implantation

“…The appearance of the clamshell lines has previously been observed in semiconductor materials, including InP, and is indicative of plastic deformation. 9 The surfaces corresponding to brittle fracture are steeper compared to conchoidal fracture surface and would be composed of various cleavage planes in InP. Figure 3a shows a histogram of the angles measured from the flat ͑100͒ surface to the angled pyramidal planes.…”

Electron microscopic observations of microcracking about indentations in aluminum oxide and silicone carbide

“…In this respect the materials studied in the present work provide an interesting contrast in that a-silicon carbide has a distinct tendency to basal cleavage while sapphire does not, the reason being that although (0001) may represent the plane intersecting the least number of bonds in the hexagonal structure a relatively large component of polarity in the bonding in the case of sapphire renders this plane unfavourable on the grounds of electrostatic attraction effects [22] . One would therefore anticipate a greater incidence of lateral venting nearly parallel to (0001) foils in the fon.j^x material; this trend was in fact apparent in the micrographs (note extensive crack plane in Figs.…”