Co-Doping of Diamond With Boron and Sulfur

Sulfur incorporation in diamond was performed by B-S co-doping method via microwave plasma chemical vapour deposition (MPCVD) technique on undoped Si as substrates. Dimethyl disulfide and boron oxide were the doping sources, which were diluted in acetone. Auger electron spectra (AES) confirmed the presence of sulfur in the films. Scanning electron microscopy (SEM), X-ray diffraction (XRD) as well as Raman scattering spectroscopy were employed to characterize the as-grown films. It was found that limit amounts of boron facilitated sulfur incorporation into diamond. The activation energy of B/S co-doped diamond films is 0.39 eV. SEM observations showed that the crystal quality of these films increases with increasing S incorporation. The observed Fourier transform infrared (FTIR) supported the existence of C, S and B bonding in the films. Even with S incorporation levels of 0.15%, measurements of films resistivity showed that the films had significant high resistance. This might reflect the defects in these polycrystalline films which could act as compensating acceptors, soaking up the donated electrons from the S.