Early stages of deposition of nitrides on cubic silicon carbide: A theoretical study

We report on the early stages of deposition of nitrides on the silicon term inated surface of cubic SiC(001), investigated by means of first principles total-energy-and-force calculations. We present results for both atomic N adsorption and thin AIN film formation. For many configurations containing N adatoms with coverages less than 1/2 monolayer, nitrogen can be adsorbed on the surface in zincblende sites. For higher coverages, zincblende adsorp tion sites for N atoms are metastable: nitrogen preferentially forms N-2 di mers, each N atom being threefold coordinated and bonded to two surface Si atoms. This leads to an N-coated SIC surface free of dangling bonds. which inhibits growth. Our results for the stability of two-dimensional AIN films confirm that nitridation of the cubic Si-terminated SiC(001) surface shoul d be avoided in order to grow thick wetting layers. The formation of a char ge neutral interface, with species intermixing, is conducive to the deposit ion of two-dimensional films. Such a mixing is achievable by starting growt h in an Al-rich ambient.