INVESTIGATION OF OPTICAL, STRUCTURAL, MORPHOLOGICAL And THERMOELECTRIC PROPERTIES OF Ge DOPED NiO THIN FILMS

Abstract

Nickel oxide thin films have been grown by reactive magnetron RF sputtering. The optical band gap has been estimated using Tauc equation and found to be decreased as the Ge dopant increase. The XRD results have suggested that the crystallinity of the NiO thin films has changed after doping with Ge, the (111) phase of NiO has disappeared after doping and another phase of NiO has exhibited (200) associated with Ge phase (220). This has suggested that the Ge dopants have sufficiently incorporated into the NiO lattice structure and changing the structure order and crystallinity. AFM and SEM have shown that surface morphology has changed after doping with Ge with rougher and grainier surface. EDX Analysis confirms the change in the lattice structure. The electrical conductivity has conducting a temperature dependency behavior. Seebeck coefficient has revealed that NiO thin film is a p-type semiconductor; while after doping it has changed to be n-type semiconductor as the Seebeck coefficient has become negative. Increasing the electrical conductivity without affecting the Seebeck coefficient has enhanced the power factor.