Abstract
A heteroepitaxial growth model of the ZnO film on sapphire(0001) is simulated using the plane wave ultrasoft pseudo-potential method based on density functional theory. It is found that interfacial atoms have different diffusivity at 400,600 and 800℃. The temperature has a decisive effect on the surface and interface structures of ZnO/α-Al2O3(0001) and on the growth mode of ZnO thin films. In the whole process of the adsorption and growth of ZnO, the diffusivity of O atoms is higher than that of Zn, and the interlayer diffusion has an important role in the homogeneous growth of the thin films. There exist two growth modes of ZnO on sapphire (0001), which is further demonstrated by theoretical calculation. The growth mode at about 400℃ has the character of mainly spiral-twisted growth with Zn hexagonal symmetry structure, and it is favorable for forming the Zn-terminated surface. In the case of 600℃, a regular in-plane growth is observed, which facilitates the O-terminated surface of the nO thin film. It can be concluded from the calculation that the number of Zn vacancies is greater than that of O in the atomic layer of ZnO film near the α-Al2O3(0001) substrate surface.
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