Effects of direct current bias on nucleation density of superhard boron-rich boron carbide films made by microwave plasma chemical vapor deposition

Abstract We report bias enhanced nucleation and growth of boron-rich deposits through systematic study the effect a negative direct current substrate during microwave plasma chemical vapor deposition. The flowing silicon with an applied −250 V was investigated for feedgas containing fixed hydrogen (H 2 ) flow rate but varying argon (Ar) rates 1330, 2670, 4000 Pa chamber pressure. For 1330 2670 Pa, goes maximum increasing Ar rate. This also corresponds to peak in temperature. However, at no or temperature is observed range tested. Using these results, pre-treatment experiments were performed Ar/H plasma, yielding current. Nucleation density boron measured after subsequent exposure B H 6 found be factor 200 times higher than when used. Experiments repeated (fixed voltage rate) order test pressure on density. Compared we find nearly 7 densities both negatively biased plasma. Results are explained by incorporating measurements optical emission use heterogeneous theory. optimal conditions used grow amorphous films hardness as high 58 GPa, well above 40 GPa threshold superhardness.