Experimental and theoretical investigations of structural and thermoelectric properties of gallium doped ZnO thin films

We performed experimental and theoretical investigations of structural and thermoelectric properties of Ga-doped ZnO thin films. We prepared the thin films by a RF magnetron sputtering with various argon gas pressures, followed by thermal annealing at 500°C for 60 min in vacuum condition. We evaluated surface morphology and crystallographic properties as the structural properties of the ZnO thin films. To estimate the thermoelectric properties, we performed Hall measurement and the measurements of electrical conductivity, Seebeck coefficient and power factor. For theoretical analysis, we estimated an energy band structure of ZnO by first-principle calculation (ABINIT) based on density function theory with local density approximation, followed by the calculation of transport properties by BoltzTraP code. As a result, we found that the thin films at 2.0 Pa obtained the highest power factor of 0.73 μW/(cm・K2). Even though the transport properties were exhibited certain differences between the experimental results and the theoretical results, we observed the approximate trend of the transport propeties of ZnO.