Electron microscopic study of precipitates and defects in germanium and silicon

Abstract

The precipitate particles and defects formed during precipitation of lithium from solid solution in germanium and silicon have been studied by transmission electron microscopy. Kinetic studies on the same systems have been reported previously. From the microscopic investigation, it has been determined that the precipitate particles in germanium are spherical, maintain a coherent interface with the parent phase, and are randomly distributed. The experimental evidence obtained from microscopy has been interpreted through the application of the theoretical work of Ashby and Brown on diffraction contrast of coherent, spherical precipitate particles. Various contrast effects in silicon have been noted. The number density of precipitate particles in germanium has been determined from electron micrographs. This number density has been compared to the number density obtained from precipitation experiments on the same sample, the precipitation number density determined using the theory of Ham on diffusion limited precipitation for spherical precipitate particles. The agreement is found to be quite good, covering a range of number densities 8 × 10 11 cm −3 to approximately 10 14 cm −3.