Formation of β-SiC nanocrystals by the relaxation of Si _1-yC_y random alloy layers

Abstract

In this work we consider the relaxation behavior of Si1-yC y random alloys grown epitaxially on Si, with 0.005≳y≳0.05. The Si1-yCy layers are under tensile strain as grown and at annealing temperatures below 900°C the relaxation of strain is achieved by dislocation formation, in a fashion similar to SiGe relaxation. However, at temperatures in excess of 900°C the C, which at lower temperatures remained in substitutional sites, precipitates out of the lattice, this removes all of the tensile strain from the layer. The nature of this precipitation is to form single crystal, nanoparticles of β-SiC with the same lattice orientation as the Si lattice in which they are created. These nanoparticles are of uniform diameter (3±1 nm for y=0.005 Si1-yCy material) and randomly dispersed throughout the original Si1-yCy region. This ability to produce nanocrystals of wide band-gap material within the Si matrix should enable the exploration of mesoscopic phenomena. The nanoparticles once formed also block the movement of dislocations, thus locking in any strain fields associated with the dislocations.