Al2O3衬底无催化剂生长GaN纳米线及其光学性能

采用一种绿色的等离子增强化学气相沉积法,以Al2O3为衬底, Ga金属为镓源, N2为氮源,在不采用催化剂的情况下,成功制备获得了结晶质量良好的GaN纳米线.研究表明,生长温度可显著调控GaN纳米线的形貌,当反应温度为950℃时,生长出的GaN微米片为六边形;当反应温度为1000℃时,生长出了长度为10-20μm的超长GaN纳米线.随着反应时间增加, GaN纳米线的长度增加. GaN纳米线内部存在着压应力,应力大小为0.84 GPa.同时,也进一步讨论了GaN纳米线无催化剂生长机制. GaN纳米线光致发光结果显示, GaN纳米线缺陷较少,结晶质量良好,在360 nm处有一个较为尖锐的本征发光峰,可应用于紫外激光器等光电子器件.本研究结果将为新型光电器件低成本绿色制备提供一个可行的技术方案.

Preparing GaN nanowires on Al2O3 substrate without catalyst and its optical property

A green and low-cost method to prepare high-quality GaN(gallium nitride) nanowires is important for the applications of GaN-based devices on a large scale. In this work, high-quality GaN nanowires are successfully prepared by a green plasma enhanced chemical vapor deposition method without catalyst, with Al2 O3 used as a substrate, metal Ga as a gallium source and N2 as a nitrogen source. The obtained GaN nanomaterials are investigated by using X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), Raman spectroscopy, and photoluminescence(PL) spectroscopy. The XRD results demonstrate that hexagonal-wurtzite GaN is obtained and no other phases exist. The SEM results show that GaN nanowires and hexagonal GaN microsheets are obtained at different temperatures. When the growth temperature is at 950 ℃(reaction time for 2 h), the hexagonal GaN microsheets each with a size of 15 μm are obtained. When the growth temperature is at 1000 ℃(reaction time for 2 h), the GaN nanowires with the lengths in a range of 10–20 μm are obtained. With the reaction temperature increasing from 0.5 h to 2 h, the lengths of GaN nanowires increase. The TEM results suggest that the GaN nanowires are of high crystallinity and the growth direction of GaN nanowires is in the 0001] direction. The Raman results indicate that there exists a compressive stress in the GaN nanowires and its value is 0.84 GPa. Meanwhile, the growth mechanism of GaN nanowires is also proposed. The morphologies of GaN nanomaterials are tailed by the growth temperature, which may be caused by Ga atomic surface diffusion. Ga atoms have low diffusion energy and small diffusion length at 950 ℃. They gather in the non-polar m-plane. The(0001) plane with the lowest energy begins to grow. Then, hexagonal GaN microsheets are obtained. When reaction temperature is at 1000 ℃, the diffusion length of Ga atoms increases. Ga atoms can diffuse into(0001) plane. In order to maintain the lowest surface energy, the GaN nanowires grow along the 0001] direction. The PL results indicate that the obtained GaN nanowires have just an intrinsic and sharp luminescence peak at 360 nm, which possesses promising applications in photoelectric devices such as ultraviolet laser emitter. Our research will also provide a low-cost and green technical method of fabricating the new photoelectric devices.