Influence of nitrogen additions on hot-filament chemical vapor deposition of diamond

The influence of N-2 additions (5%-40% N-2/CH4) on various features of hot-filament chemical vapor deposition (CVD) of diamond layers is presented and discussed using experimental results and calculations of the thermodynamic equilibrium. Small N-2 additions (5%-10% N-2/CH4) improved the diamond phase purity but led surprisingly either to an increase or decrease of the growth rate depending upon the filament temperature. The effects are attributed to a reduction of carbon supersaturation due to an abstraction of adsorbed hydrogen atoms caused by CN and HCN. Higher N-2 additions (20%-40% N-2/CH4) revealed a deterioration of the diamond phase purity and reversal growth rates. These results are probably caused by a beginning reconstruction of the diamond surface which is originated from enhanced abstraction of adsorbed hydrogen and the inefficiency of CN or nitrogen species to stabilize the diamond surface structure. (C) 1996 American Institute of Physics.