Ge-rich Si_(1-x)Ge_x Nanocrystal Formation by the Oxidation of As-Deposited Thin Amorphous Si_0.7Ge_0.3 Layer

摘要

Ge-rich Si_(1-x)Ge_x nanocrystals are formed by the selective oxidation of Si during the dry oxidation of an amorphous Si_(0.7)Ge_(0.3) layer. The oxidation kinetics of the alloy film shows the activation energies of linear and parabolic rate constants are about 1.35 and 1.02 eV, respectively, based on the model proposed by Deal and Grove. In addition, as a result of the selective oxidation of Si and Ge pile-up during the oxidation process, Ge-rich Si_(1-x)Ge_x nanocrystals are formed with the size of 5.6+- 1.7 nm and the spatial density of 3.6x10~(11) /cm~2 at 600 ℃. At higher temperature of 700 and 800℃, the size of nanocrystal is increased to about 20 nm. The nanocrystals formation by oxidation is thought to be due to higher oxidation rate at grain boundary than at bulk grain. Therefore, the dependence of size on temperature is explained with the grain size determined by solid phase crystallization of amorphous film, oxidation rate, and grain growth.