Research On The Zno Films Grown On High Thermal Conductivity Graphite Substrate By Ultrasonic Spray Pyrolysis

ZnO is a Ⅱ-Ⅵ semiconductor material with direct gap. At room temperature, the band gap is3.37eV, and the exciton binding energy is so large of60meV relatively. At the same time ZnO has excellent ptical and electrical properties. It has been regarded as a promising candidate for the next generation of short-wavelength light emitting diode(LED) and lasing devices. The methods to fabricate ZnO are numerous, such as chemical vapor deposition (CVD), molecular beam epitaxy(MBE), sputtering, pulsed laser deposition (PLD), vapor phase transport (VPT), thermal evaporation and ultrasonic spray pyrolysis. Among these methods, ultrasonic spray pyrolysis has got a lot of attention, due to its outstanding advantages sush as low cost, easy operation, and the experiment condition in the atmospheric.Although great progress has been made in the control of background conductivity of ZnO and demonstrations of p-type doping, some difficulties remain challenging and unresolved. For example, one particular issue for application as high-power devices is the severe heat dissipation problem, and how to select the substrate is the key to solve the problem. In addition, for some special applications such as large area foldable and high-power devices, it is necessary to transfer crystalline ZnO films onto foreign substrates, such as flexible plastic or metal substrates, And how to separate the ZnO thin film from the substrate is a other problem. Considering the multilayer structure of the graphite and low thermal resistance characteristics, can choose graphite as the growth of ZnO thin film substrate. Considering that graphite is a multi-layer system with nearly decoupled2D graphene planes and has the property of low thermal resistance, we choose the graphite as the substrate.ZnO thin films were deposited on graphite substrates by ultrasonic spray pyrolysis method with Zn(CH3COO)2·2H2O aqueous solution as precursor. The crystalline structure, morphology, and optical properties of the as-grown ZnO films were investigated systemically as a function of deposition temperature and growth time. In room temperature photoluminescence spectra we observed near-band edge ultraviolet (UV) emission for the optimized samples, yet nearly did not detected the usually observed defect related deep level emissions. It indicated that high optical quality ZnO thin films could be achieved via this ultrasonic spray pyrolysis method. Considering the features of transferable and low thermal resistance of the graphite substrates, the achievement will be of special interest for the development of high-power semiconductor devices with sufficient power durability.