Structural and thermoelectric properties of Al-doped ZnO thin films grown by chemical and physical methods

Aluminum doped zinc oxide (AZO) thin films have become technologically important materials due to their application potential for thermoelectric devices. In this paper, AZO thin films are deposited on the glass substrates using the solution derived by sol-gel route for dip-coating cycles and the radio-frequency sputtering process. The crystalline structure of two types of AZO films is characterized by X-ray diffraction exhibiting the typical hexagonal wurzite structure of ZnO. The rough surface of the heat treated films are observed by the SEM image. The average grain size of obtained films is evaluated based on these investigations showing they are consistent with each other. The sheet resistivity and Seebeck coefficient are measured between room temperature and 400 degrees C and used to determine the electrical conductivity and power factor of all films. The obtained results provide the advantages and disadvantages of the prepared films by each method for aiming at thermoelectrical applications.