Hao Lanzhong

Rectifying the Current-Voltage Characteristics of a LiNbO3 Film/GaN Heterojunction

Epitaxial LiNbO3 (LNO) films are grown on n-type GaN semiconductor substrates, forming LNO/GaN p-n junctions. The current-voltage (I—V) and capacitance-voltage (C—V) characteristics of the junctions are studied. The I—V curve shows a clear rectifying property with a turn-on voltage of 2.4 V. For the forward voltages, the conduction mechanism transits from Schottky thermionic emission for low voltages to space-charge-limited current for large voltages. Reverse C—V characteristics exhibit a linear 1/C2 versus V plot, from which a built-in potential of 0.34 V is deduced. These results are explained using the energy-band structure of the LNO/GaN junction.

Effect of thickness on the microstructure of GaN films on Al2O3 (0001) by laser molecular beam epitaxy

Heteroepitaxial GaN films are grown on sapphire (0001) substrates using laser molecular beam epitaxy. The growth processes are in-situ monitored by reflection high energy electron diffraction. It is revealed that the growth mode of GaN transformed from three-dimensional (3D) island mode to two-dimensional (2D) layer-by-layer mode with the increase of thickness. This paper investigates the interfacial strain relaxation of GaN films by analysing their diffraction patterns. Calculation shows that the strain is completely relaxed when the thickness reaches 15 nm. The surface morphology evolution indicates that island merging and reduction of the island-edge barrier provide an effective way to make GaN films follow a 2D layer-by-layer growth mode. The 110-nm GaN films with a 2D growth mode have smooth regular hexagonal shapes. The X-ray diffraction indicates that thickness has a significant effect on the crystallized quality of GaN thin films.

MoS 2 修饰TiO 2 纳米管阵列光电化学性能研究

通过阳极氧化法在乙二醇电解液中制备TiO 2 纳米管阵列, 以钼酸钠和硫脲作为钼源和硫源, 并添加半胱氨酸为辅助剂, 水热法制备纳米花状二硫化钼修饰的TiO 2 纳米管阵列。用X射线衍射仪、扫描电子显微镜、能谱仪和拉曼光谱对复合材料的晶型、形貌、物相等进行分析, 通过电化学工作站测试复合材料的线性扫描伏安曲线、电化学阻抗谱和莫特–肖特基曲线。结果表明: MoS 2 /TiO 2 复合材料形貌比较规整均匀, MoS 2 纳米花尺寸约为200 nm; MoS 2 与TiO 2 复合有利于形成异质结, 促进光生电子和空穴的分离; 当钼酸钠浓度为0.8 mmol/L时制备的复合材料光化学能转化率为纯氧化钛的2.89倍, 达到了1.65%, 而且复合材料的电荷转移电阻降低了约50%, 光生载流子浓度提高了24倍, 达到了3.38×10 23 cm -3 , 具有非常优异的光电化学性能。通过阳极氧化法在乙二醇电解液中制备TiO 2 纳米管阵列, 以钼酸钠和硫脲作为钼源和硫源, 并添加半胱氨酸为辅助剂, 水热法制备纳米花状二硫化钼修饰的TiO 2 纳米管阵列。用X射线衍射仪、扫描电子显微镜、能谱仪和拉曼光谱对复合材料的晶型、形貌、物相等进行分析, 通过电化学工作站测试复合材料的线性扫描伏安曲线、电化学阻抗谱和莫特–肖特基曲线。结果表明: MoS 2 /TiO 2 复合材料形貌比较规整均匀, MoS 2 纳米花尺寸约为200 nm; MoS 2 与TiO 2 复合有利于形成异质结, 促进光生电子和空穴的分离; 当钼酸钠浓度为0.8 mmol/L时制备的复合材料光化学能转化率为纯氧化钛的2.89倍, 达到了1.65%, 而且复合材料的电荷转移电阻降低了约50%, 光生载流子浓度提高了24倍, 达到了3.38×10 23 cm -3 , 具有非常优异的光电化学性能。