Effect of oxygen on the optical, electrical and structural properties of mixed-phase boron doped nanocrystalline silicon oxide thin films

Abstract Systematic investigation on the optoelectronic and structural changes occurring in the p–nc-Si network due to the inclusion of oxygen into the initial crystalline-like matrix has been done. The incorporation of O into the Si network occurs via the Si–O–Si bond which is effectively responsible for the widening of optical band gap. B incorporation takes place via the B–Si bonds as well as the B–O bonds which increases at enhanced CO2 dilution to the plasma. The continuously increased intensity of (SiH2)n wagging and Si-H2 bending mode in p–nc-SiOx films indicates poly-hydrogenation as inherent to the increasing oxygen alloying of the network. Two stage activation energies across around 340 K in the temperature dependent dark conductivity identify prominent two phase structure of the p–nc-SiOx material, the Si-ncs being embedded within amorphous p–SiOx matrix. The p–nc-SiOx film grown by typical 13.56 MHz PE-CVD at a low growth temperature ∼170 °C and optimized with a convincingly good combination of the electrical conductivity (σD ∼6.8 × 10−2 S cm−1), optical band gap (Eg ∼1.91 eV) and volume fraction (XC ∼54%) of the Si crystallinity containing CH