Influence of Positive Bias on Electrical Properties of Undoped Nanocrystalline Diamond Films

By means of electron assisted hot filament chemical vapour deposition technology, nanocrystalline diamond films are deposited on polished n-(100)Si wafer surface at 1kPa gas pressure. The deposited films are characterized with a Raman spectrometer, atomic force microscope, semiconductor characterization system and Hall effect measurement system. The results show that, when bias current is larger than 2A, sheet hole concentration can increase to a value greater than 10¹³cm^-2 and undoped nanocrystalline diamond films with a p-type semiconducting characteristic form. Heterojunction between n-Si substrate and the nanocrystalline diamond films deposited with 2A and 6A bias current has an evident junction effect. Hole formation mechanisms in the films are discussed.