Diamond growth by injecting thermally decomposed chlorine atoms into methane/hydrogen mixture

Abstract

Crystalline diamond has been successfully deposited by injecting thermally decomposed Cl atoms into CH4/H2 in a hot-tube system at an extremely high flow velocity (in the convection-dominant mass transport region). Diamond growth rate increased with increasing the total flow rate, suggesting the increase of [Cl]/[H] ratio near the growth surface. Film quality also improved with increasing the total flow rate as well as reducing the reactor pressure. Both the quality and film growth rate were enhanced as the inlet [Cl2] increased, due to the increase of total radical concentration. Two distinct growth activation energies were measured ranging from 3.6 kcal/mol in the substrate temperature range of 600–750 °C to 7.9 kcal/mol in the temperature range of 400–600 °C. Owing to the extremely short residence time and low gas temperature, carbon species near the growth surface remained almost the same as the input carbon source. By employing almost pure CH4 or C2H2 near the substrate surface, the CH3 radical was shown to be a more efficient diamond growth precursor than C2H2. With almost pure C2H2 near the surface, diamond deposition was negligible in a wide range of conditions on either silicon or diamond surfaces.