Rapid thermal processing induced interfacial diffusion and solid reaction in the Al₂O₃/ZnO nano-laminates films

Al₂O₃/ZnO nanolaminates are promising for thin-film transistors and photoluminescence applications. In this work, the thermal induced interface changes of Al₂O₃/ZnO nanolaminates were studied as a function of the in site deposition temperature and rapid post-annealing temperature. The Al₂O₃/ZnO nanolaminates were grown by atomic layer deposition system at 80 °C, 120 °C, and 250 °C, and further post-annealed in a rapid thermal processing (RTP) furnace at 600 °C, 700 °C, and 800 °C for 10 min, separately. Then the microstructures, interfacial diffusion and solid-phase reactions of the Al₂O₃/ZnO nanolayers were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM). The results show that the in situ growth temperature directly affects the crystallinity and selective orientation of the ZnO interlayers, which further induce the ZnO interlayers to undergo completely different interfacial diffusion and solid-phase reactions during the rapid post-annealing processing. The films grown at 80 °C were close to amorphous, while those grown at 120 °C had a distinctly dominant orientation and exhibited better crystallization at 250 °C. The presence of the ZnAl₂O₄ grains indicates the solid-phase reactions have occurred on the ZnO/Al₂O₃ interface during the rapid post-annealing at 700 °C or above.