Dependence of the physical properties of GaZnO/polyethersulfone on the Ar Gas flow rate during sputtering deposition process

The effects of Ar gas flow rate during the sputtering deposition of Ga-doped ZnO thin films, which were grown on polyethersulfone substrates, on their physical properties were investigated. For measurements of X-ray diffraction, samples deposited under higher Ar gas flux showed the relevant ZnO (002) peak while samples deposited under lower Ar gas flux revealed ZnGa ₂O₄ (311) secondary phase. The samples showed a quite strong dependency of the electrical resistivity on the Ar gas flux; i.e., samples deposited under higher Ar gas flux showed a lower resistivity, but samples deposited under lower Ar gas flux showed a quite high resistivity. This result was confirmed to originate from the insulating behavior of the unexpectedly formed ZnGa₂O₄ spinels. The formation of ZnGa₂O₄ spinels might result from the generation of metastable radicals during the sputtering process because supplying an unduly insufficient amount of Ar gas gives rise to a bombardment of metastable species from the target material.