Electron Momentum Distribution in Silicon and Germanium by Positron Annihilation

Abstract

The angular correlation of positron-annihilation radiation from single crystals of silicon and germanium has been measured for three different orientations of each crystal. The distributions for the three orientations differ greatly from one another, but each germanium distribution differs from the corresponding silicon distribution only by a scale factor which arises from the difference in the lattice constant. Data are compared with curves calculated using the nearly free-electron approximation for the electron's momentum. It is assumed that the occupied electron states in the crystal fill the Jones zone, a regular dodecahedron bounded by the set of {220} planes in momentum space, and the energy gap is taken to be an adjustable parameter. The fit is extremely good for the radiation emitted in the (110) plane but not so good for the (111) and (100) orientations. Possible reasons for the discrepancies are discussed.

Pressure-induced transitions in solid nitrogen: Role of dispersive interactions

“…The positron-annihilation results 38 were qualitatively reproduced in a pioneering model-potential study by Stroud and Ehrenreich. 43 The results obtained by Seth and Ellis 44 with a Hartree-Fock-Slater variational method appear to be in reasonable agreement with the results of Reed and Eisenberger, 39 except for an overestimation by about 1.5% in the region of small p values.…”

“…1,37 The history of experimental determinations of silicon CPs has been long and fruitful. Since the first experimental work, based on positron-annihilation measurements, 38 through the γ -ray study by Reed and Eisenberger, 39 which, for many years, was the benchmark in this field, through the work of Pattison et al, 40 Shiotani et al, 41 and Kubo et al, 42 up to the present data, the experimental resolution has progressively improved, resulting in enhancement of the CP anisotropies.…”

Correlation Effects in the Compton Profile of Silicon

“…Silicon momentum densities and Compton profiles have been studied experimentally with various techniques such as synchrotron radiation x-ray scattering [10,11], g-ray scattering [12][13][14][15][16], and angular correlation of positron annihilation [17][18][19]. There have also been many theoretical computations of these quantities, ranging in complexity from tight-binding [20], empirical pseudopotential [21] to ab initio pseudopotential [22] and allelectron methods [23,24].…”

Effects of stoichiometries on the positron distribution in Si1–x–yGexCy alloys

“…In recent years several investigations have been reported in which the positron was used as a probe for studying the electronic properties of solids [19][20][21][22]. It has been shown that the positron charge density can yield considerable information about the bonding properties of simple, binary, and semiconductor alloys [23][24][25][26][27].…”