Properties of conductive zinc oxide films for transparent electrode applications prepared by rf magnetron sputtering

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Abstract
High-quality zinc oxide (ZnO) films have been deposited by rf magnetron sputtering from a zinc oxide target. The material has been obtained with resistivities ranging from about 1 Ω cm to 4.6×10−4 Ω cm, whereas the average transmission was always greater than 90% between 400 and 800 nm. A relatively high deposition rate usually leads to low resistivity of films. The films with the lowest resistivity differ from higher-resistivity films by their surface morphology, as observed by scanning electron microscopy and by their x-ray diffraction pattern. In particular, good quality films have a diffraction peak at 2Θ≂30.5°. The best films have also been characterized by Hall-effect measurements, Auger electron spectroscopy, and infrared transmission data. It is suggested that the film properties are dependent on the flux of energetic neutral oxygen atoms to the growing surface, which can be varied by changing the sputtering conditions, such as the target to substrate distance. These films have considerable potential in amorphous silicon solar cell technology as well as other photovoltaic and nonphotovoltaic applications.