Electrical and optical properties of zinc oxide thin films prepared by rf magnetron sputtering for transparent electrode applications

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Abstract
Zinc oxide films were prepared on unheated glass substrates by rf magnetron sputtering under an applied external dc magnetic field in pure argon gas, and electrical and optical properties of the deposited films were investigated. Highly transparent films with resistivity as low as 10−4 Ω cm, which were weakly oriented perpendicular to the substrate surface(c-axis orientation), could be produced with a relatively high deposition rate on the substrate suspended perpendicular to the target surface by controlling the sputtering gas pressure and the external dc magnetic field, without any postdeposition preparative treatment. The Hall mobility of the film with the highest conductivity was about 120 cm2/V sec, which was the highest yet reported for thin films on ZnO. The increase in the conductivity was related to the increase in Hall mobility which was caused by the decrease of carrier scattering from grain boundaries due to the grain growth resulting from the improvement of crystallization. The improvement of crystallization is resulted from particles with a momentum component parallel to the substrate surface. The sputtered ZnO films should be useful as a less expensive window material.