Fabrication of epitaxial ZnO films by atomic-layer deposition with interrupted flow

We formed epitaxial ZnO thin films on a (0001) c-plane sapphire substrate through deposition of atomic layers (ALD) at 25–160 °C using diethylzinc (DEZn) and deionized water as precursors in combination with interrupted flow. High-resolution X-ray diffraction measurements were employed to characterize the microstructure of these films. With interrupted flow, we obtained ZnO thin films with an optimal growth window in a range of 40–160 °C, effectively decreasing the growth temperature by about 120 °C relative to a conventional method involving continuous flow. X-ray reflectivity measurements showed that the rate of growth increased also between 20 °C and 120 °C. The XRD results indicate that the stock time might extend the reaction of DEZn and water through an increased duration. All results show that a low temperature for growth improves the crystalline quality and is consistent with thermodynamically blocked self-compensation.