ZnO epitaxial films were grown on sapphire substrates by molecular beam epitaxy. The diffraction pattern shows an extremely strong ZnO (0002) peak at 34.43 degrees with a full width half-maximum of 0.19 degrees. Low resistivity and highly transparent indium tin oxide (ITO), RuOx(1 <= x <= 2), and TiW ohmic contact were achieved by radio frequency sputtering and annealing treatment. The transmittance of 450 degrees C-annealed ITO, 650 degrees C-annealed Ru, and 200 degrees C-annealed TiW were measured to be 94, 68, and 61%, respectively, with a wavelength of 400 nm. Moreover, the resistivities of 450 degrees C-annealed ITO, 650 degrees C-annealed Ru, and 200 degrees C-annealed TiW were measured to be 9.2 X 10(-5), 4.1 X 10(-5), and 4.7 X 10(-3) Omega cm, respectively. Finally, the specific contact resistance of 450 degrees C-annealed ITO, 650 degrees C-annealed Ru, and 200 degrees C-annealed TiW on ZnO films was estimated to be 2.15 X 10(-4), 2.72 X 10(-4), and 2.56 X 10(-4) Omega cm(2), respectively, by circular transmission line model method. (c) 2005 The Electrochemical Society.