Deposition and boron doping of nano-crystalline diamond thin films on poly-crystalline diamond thick films

摘要

Boron-doped nano-crystalline diamond (NCD) thin films have been successfully deposited on well-polished poly-crystalline diamond (PCD) thick films in a microwave plasma enhanced chemical vapor deposition (MPCVD) reactor for the first time. Different surface pretreatment techniques are carried out under different gas conditions (CH 4, H 2, Ar, and CH 4/H 2) to eliminate the effect of grain boundaries on the growth of a smooth NCD intrinsic layer. Well doped NCD films have been fabricated in CH 4/H 2/B 2H 6 plasma by varying the atomic ratio of B/C and the substrate temperature. Atomic force microscopy (AFM) results show that pretreatment in pure CH 4 plasma at 1000°C is most effective for NCD growth, while hydrogen containing plasma is harmful to the surface smoothness of NCD thin films. Doping research indicates that the optimum parameters for the boron-doping of high-quality NCD thin films are B/C=300 ppm (10 -6) and 800°C.