Atomic Structure and Diffusion in Amorphous Si-B-C-N by Molecular Dynamics Simulation

Abstract

We carried out molecular dynamics simulation of amorphous silicon nitride containing boron and carbon, in order to investigate the short-range atomic arrangement and diffusion behavior. In amorphous Si–B–N, boron atoms are in a nearly threefold coordinated state with nitrogen atoms, while boron atoms in amorphous Si–B–C–N have bonding with both carbon and nitrogen atoms. Carbon atoms in Si–B–C–N are also bonded to silicon atoms. The self-diffusion constant of nitrogen in Si–B–N becomes much smaller than that in amorphous Si3N4. Also, amorphous Si–B–C–N exhibits smaller self-diffusion constants of constituent atoms, even compared to Si–B–N. Addition of boron and carbon is important in decreasing atomic mobility in amorphous Si–B–C–N. This may explain the increased thermal stability of the amorphous state observed experimentally.