Preparation of boron doped diamond-like carbon films in a low-pressure high-density plasma in RF ICP-CVD

The main objective of this work is to prepare electrically conducting boron doped diamond-like carbon (DLC) films with good crystalline qualities and high optical band gap in a low pressure and high-density plasma in an RF ICP CVD system. The main precursor gas used was CH4, with Ar being the diluent gas. B2H6 in He was used as the main source of boron, as the dopant, in the system. Planar inductively coupled technique enables the plasma to be ignited at a very low deposition pressure of 30 mTorr. A substrate temperature of 450 °C, a 900 W of RF power and a dc substrate bias of −40 V were used during the sample growth. By varying the B2H6/CH4 (=R) ratio, the optimized condition for preparing boron doped DLC thin films was obtained at R = 1. Raman analysis showed that this sample has the minimum ID/IG ratio ∼0.83, a maximum IDia/ID (∼1.18) and a maximum IDia/IG (∼0.98). The sp3 C-C content of 48.05% was calculated from XPS. A high optical band gap of ∼3.8 eV was obtained from the UV–Vis spectra. Boron doping was confirmed from the Raman, XPS and electrical conductivity measurements.