Synthesis of boron-doped diamond films by DC plasma CVD using a CH4+CO2+H2 gas mixture at lower substrate temperature and formation of an n-Si/p-diamond heterojunction

Diamond films were synthesized by direct current plasma chemical vapour deposition using a CH₄+CO₂+H₂ gas mixture on Si substrates. The optimum deposition conditions were determined. It was found that 0.4 A/cm² current density, at applied voltage of 1 kV, resulted in good-quality diamond films. The substrate temperature was 750 K which is considerably lower than the conventional requirement of ∼1100 K. Boron doping was achieved by passing a portion of the gas mixture through boric acid dissolved in methanol. The boron-doped p-type diamond films were deposited on an n-type single crystalline Si substrate and an n-Si/p-diamond heterojunction was fabricated. The p-n junction was characterized in terms of current-voltage (I-V) and capacitance-voltage (C-V) measurements.