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The structure, metal-insulator transition (MIT), and related Terahertz (THz) transmission characteristics of VO 2 thin films obtained by sputtering deposition on c-, r-, and m-plane sapphire substrates were investigated by different techniques. On c-sapphire, monoclinic VO 2 films were characterized to be epitaxial films with triple domain structure caused by β-angle mismatch. Monoclinic VO 2 β angle of 122.2 and the two angles of V 4+–V 4+ chain deviating from the a m axis of 4.4 and 4.3 are determined. On r-sapphire, tetragonal VO 2 was determined to be epitaxially deposited with VO 2 (011) T perpendicular to the growth direction, while the structural phase transformation into lower symmetric monoclinic phase results in (2 11) and (200) orientations forming a twinned structure. VO 2 on m-sapphire has several growth orientations, related with the uneven substrate surface and possible inter-diffusion between film …