Synthesis of Nanostructured Diamond via Controlled Surface Pretreatment in Hexane Medium

Abstract
The grain density of chemical vapor deposition (CVD) diamond film is greatly enhanced via controlled surface pretreatment in hexane medium under ultrasonic irradiation. Surface treatment of the substrate prior to the deposition is essential for continuous diamond film formation by CVD processing. Generally the pretreatment is carried out using diamond powder dispersed in alcohol or acetone medium under ultrasonic irradiation. In this study we used hexane as a dispersion medium, and synthesized diamond on a silicon wafer by conventional microwave plasma-enhanced CVD (MPCVD). The grain size of a continuous film whose substrate is treated in hexane is successfully reduced to ∼100 nm. The corresponding grain density is enhanced to ∼1010/cm2. The diamond film is homogeneously blue in color. When the substrate is treated in acetone, the density is in the range of 108/cm2 under the same synthesis conditions.