The effect of negative bias on the preparation conditions and structural changes in boron-doped nanocrystalline silicon thin films prepared on PET

In this work, the fabrication of boron-doped nanocrystalline silicon (nc-Si) deposited on PET substrate at room temperature are reported. Negative substrate bias is applied during deposition for improving the crystallinity of samples. The effects of negative bias on the structural, electrical and optical properties of B-doped nc-Si thin films prepared on PET are systemically studied through various characterizations. XRD and Raman results show that a phase transition from amorphous phase to crystalline phase takes place at negative bias = 80 V. By using moderate negative bias, the crystalline volume fraction can be effectively improved. The electrical properties have been found related to the crystalline volume fraction. At negative bias = 120 V, the maximum values of dark conductivity (1.94 S/cm) and carrier concentration (7.4 × 1019 cm− 3) are obtained for the sample which has the largest crystalline volume fraction. Furthermore, the promotion mechanism on B-doping was illustrated in this paper.