Direct deposition of textured ZnO:Al TCO films by rf sputtering method for thin film solar cells

Textured thin films ZnO has been successfully grown by rf magnetron sputtering method using a special technique of introducing a small amount of water and methanol on the deposition chamber. The surface morphology of the films has pyramidal structure and the degree of texture is dependent on the Ar ambient pressure. The pressure in this experiment varied from 50 mTorr to 5 mTorr and the highest grain size of the film is obtained at 5 mTorr. The total transmittance of the films are more than 85% in the wavelength of 400 to 800nm, and haze ratio of about 14% is obtained at 400nm wavelength. Beside the textured surface, these films also have very low resistivity, lower than 1.4 /spl times/ 10/sup -3/ /spl Omega/cm. X-ray diffraction (XRD) analysis of the films showed the clear change of film growth from columnar to granular growth when the water or methanol was added during sputtering process. The granular growth of the films was closely related to the amount of OH molecules in the films.