X-RAY STUDIES OF THE BOND CHARGE PRESSURE DEPENDENCE IN SILICON AND INDIUM-ANTIMONIDE

DALE RICHARD YODER-SHORT, Purdue University

Abstract

The pressure dependence of the valence charge densities in silicon and indium antimonide were studied using X-ray diffraction methods. This was done by measuring the integrated intensity of the "forbidden" (222)-reflection as a function of pressure up to the metallic transition point for each of these materials. These measurements were performed using a single crystal mounted in a high pressure diamond anvil cell of the type developed at the National Bureau of Standards. We found that the bond charge density increases slightly with pressure (silicon) or remains about constant (indium antimonide) up to pressures approaching the metallic transition. Near the transition point (130 kbars for silicon and 30 kbars for indium antimonide) the bond electron wavefunction begins to diffuse into the crystal while the material still retains its low pressure crystalline phase. This is evidenced by a large measured decrease in the (222) integrated intensity near the transition point with no significant change in the (111) integrated intensity until the transition point is reached. Until the present very little theoretical or experimental work has been done on the problem of the bond charge density dependence on pressure or on the lattice parameter of these materials.

Degree

Ph.D.

Subject Area

Condensation

COinS