Bian Jiming

Preparation and Characteristics of GaN Films on Freestanding CVD Thick Diamond Films

Prefer-oriented and fine grained polycrystalline GaN films are prepared by plasma enhanced metal organic chemical vapour deposition on nucleation surfaces of freestanding thick diamond films. The characteristics of the GaN films are characterized by x-ray diffraction, reflection high energy electron diffraction and atomic force microscopy. The results indicate that the structure and morphology of the films are strongly dependent on the deposition temperature. The most significant improvements in morphological and structural properties of GaN films are obtained under the proper deposition temperature of 400?C.

Enhanced p-Type ZnO Films through Nitrogen and Argentum Codoping Grown by Ultrasonic Spray Pyrolysis

The N–Ag codoped ZnO films are deposited on quartz glass substrates by ultrasonic spray pyrolysis technology. The results indicate that the p-type conductivity in ZnO films is greatly enhanced by the double acceptor codoping of N and Ag compared with that of Ag- and N-monodoped ZnO films, and the N–Ag codoped low-resistivity p-type ZnO films with the resistivity of 1.05 Q-cm, relatively high carrier concentration of 5.43 × 1017 cm-3, and Hall mobility of 10.09 cm2 V-1s-1 are obtained under optimized conditions. This achievement confirms that p-type ZnO with acceptable properties for optoelectronic applications could be realized by simultaneous codoping with two potential acceptors.

The Preparation and Characteristics of InxGa1?xN (0.06 ? x ? 0.58) Films Deposited by ECR-PEMOCVD

We investigate the structural property and surface morphology of InxGa1−xN films for In compositions ranging from 0.06 to 0.58, which are deposited by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The results of x-ray diffraction (XRD) in InGaN films confirm that they have excellent c-axis orientation. The In content in the InGaN epilayers is checked by electron probe microanalysis (EPMA), which reveals that In fractions determined by XRD are in good agreement with the EPMA results. Atomic force microscopy measurements reveal that the grown films have a surface roughness that varies between 4.16 and 8.14nm. The results suggest that it is possible to deposit high-c-axis-orientation InGaN films with different In contents.

Effect of Different Substrate Temperature on Sb-Doped ZnO Thin Films Prepared by Pulsed Laser Deposition on Sapphire Substrates

Sb-doped ZnO thin films are deposited on c-plane sapphire substrates by pulsed laser deposition. Hall results indicate that the conductivity of the Sb-doped ZnO thin films is strongly dependent on the substrate temperature. The sample deposited at the temperature of 550°C exhibits p-type conductivity. It gives a resistivity of 15.25 Ω cm, with a Hall mobility of 1.79cm2V−1s−1 and a carrier concentration of 2.290 × 1017 cm−3 at room temperature. The x-ray diffraction indicates that the Sb-doped ZnO thin films deposited in the range of 450–650°C are high c-axis oriented. Low-temperature photoluminescence spectra indicate that the sample deposited at 550°C shows the strong acceptor-bound exciton (A0X) emission.

Realization of Ultraviolet Electroluminescence from ZnO Homojunction Fabricated on Silicon Substrate with p-Type ZnO:N Layer Formed by Radical N2O Doping

ZnO homojunction light-emitting diodes are fabricated on Si(100) substrates by plasma assisted metal organic chemical vapour deposition. A p-type layer of nitrogen-doped ZnO film is formed using radical N2O as the acceptor precursor. The n-type ZnO layer is composed of un-doped ZnO film. The device exhibits desirable rectifying behaviour with a turn-on voltage of 3.3V and a reverse breakdown voltage higher than 6V. Distinct electroluminescence emissions centred at 395 nm and 490 nm are detected from this device at forward current higher than 20 mA at room temperature.

Effect of Different Substrate Temperature on Phosphorus-Doped ZnO Thin Films Prepared by PLD on Sapphire Substrates

Phosphorus-doped ZnO (ZnO:P) thin films are deposited on a c-plane sapphire in oxygen at 350°C, 450°C, 550°C and 650°C, respectively, by pulsed laser deposition (PLD), then all the ZnO:P samples are annealed at 650°C in oxygen with a pressure of 1 × 105 Pa. X-ray diffraction measurements indicate that the crystalline quality of the ZnO:P thin films is improved with the increasing substrate temperature from 350°C to 550°C. With a further increase of the deposition temperature, the crystalline quality of the ZnO:P sample is degraded. The measurements of low-temperature photoluminescence spectra demonstrate that the samples deposited at the substrate temperatures of 350°C and 450°C show a strong acceptor-bound exciton (A°X) emission. The electrical properties of ZnO:P films strongly depend on the deposition temperature. The ZnO:P samples deposited at 350°C and 450°C exhibit p-type conductivity. The p-type ZnO:P film deposited at 450°C shows a resistivity of 1.846 Ωcm and a relatively high hole concentration of 5.100 × 1017 cm−3 at room temperature.

MBE技术蓝宝石衬底上生长VO 2 薄膜及其太赫兹和金属–绝缘体相变特性研究

采用分子束外延(MBE)技术在单晶蓝宝石衬底上生长了高质量化学计量比二氧化钒(VO 2 )薄膜, 通过该技术实现薄膜厚度15~60 nm精确控制。对于优化条件下VO 2 薄膜, 实现了电阻率变化超过4个数量级的优异金属–绝缘体相变, 近似于之前报道高质量单晶VO 2 相变特性。特别是通过太赫兹时域光谱分析了不同厚度的VO 2 薄膜在太赫兹波段的光学特性。结果表明: VO 2 薄膜的厚度对其在太赫兹波段的光学特性有很大影响。因此, 为了获得更优的可靠性和重复性能, VO 2 薄膜的厚度必须得到精确控制。本研究结果对于下一步VO 2 基太赫兹器件研究具有重要意义。采用分子束外延(MBE)技术在单晶蓝宝石衬底上生长了高质量化学计量比二氧化钒(VO 2 )薄膜, 通过该技术实现薄膜厚度15~60 nm精确控制。对于优化条件下VO 2 薄膜, 实现了电阻率变化超过4个数量级的优异金属–绝缘体相变, 近似于之前报道高质量单晶VO 2 相变特性。特别是通过太赫兹时域光谱分析了不同厚度的VO 2 薄膜在太赫兹波段的光学特性。结果表明: VO 2 薄膜的厚度对其在太赫兹波段的光学特性有很大影响。因此, 为了获得更优的可靠性和重复性能, VO 2 薄膜的厚度必须得到精确控制。本研究结果对于下一步VO 2 基太赫兹器件研究具有重要意义。

Terahertz and Metal-insulator Transition Properties of VO

采用分子束外延(MBE)技术在单晶蓝宝石衬底上生长了高质量化学计量比二氧化钒(VO 2 )薄膜, 通过该技术实现薄膜厚度15~60 nm精确控制。对于优化条件下VO 2 薄膜, 实现了电阻率变化超过4个数量级的优异金属–绝缘体相变, 近似于之前报道高质量单晶VO 2 相变特性。特别是通过太赫兹时域光谱分析了不同厚度的VO 2 薄膜在太赫兹波段的光学特性。结果表明: VO 2 薄膜的厚度对其在太赫兹波段的光学特性有很大影响。因此, 为了获得更优的可靠性和重复性能, VO 2 薄膜的厚度必须得到精确控制。本研究结果对于下一步VO 2 基太赫兹器件研究具有重要意义。采用分子束外延(MBE)技术在单晶蓝宝石衬底上生长了高质量化学计量比二氧化钒(VO 2 )薄膜, 通过该技术实现薄膜厚度15~60 nm精确控制。对于优化条件下VO 2 薄膜, 实现了电阻率变化超过4个数量级的优异金属–绝缘体相变, 近似于之前报道高质量单晶VO 2 相变特性。特别是通过太赫兹时域光谱分析了不同厚度的VO 2 薄膜在太赫兹波段的光学特性。结果表明: VO 2 薄膜的厚度对其在太赫兹波段的光学特性有很大影响。因此, 为了获得更优的可靠性和重复性能, VO 2 薄膜的厚度必须得到精确控制。本研究结果对于下一步VO 2 基太赫兹器件研究具有重要意义。

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本研究采用平面硅与纳米硅分别与旋涂法生长的[6,6]-苯基C61-丁酸甲酯(PCBM)形成有机–无机杂化异质结,对比研究了两种异质结界面电学特性的差异。结果显示, 平面Si/PCBM和纳米Si/PCBM两种异质结都表现出明显的整流特性, 但相对于平面Si/PCBM异质结, 纳米Si/PCBM异质结有较大的导通电压和较小的电流密度。为了深入研究导致这种差异的相关物理机制, 通过阻抗谱(IS)表征技术进一步研究了两种异质结因界面变化而产生的电阻、电容的变化趋势。阻抗测试分析表明, Si/PCBM异质结界面存在的大量缺陷致使寄生效应进一步增大, 影响了器件中电荷的输运

gt;2

Gallium nitride (GaN) films were deposited on stainless steel substrates by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition system (ECR-PEMOCVD), with trimethyl gallium (TMGa) and N2 applied as the precursors of Ga and N, respectively. The effect of growth temperature on the characteristics of GaN films is systematically investigated by reflection high energy electron diffraction (RHEED), X-ray diffraction analysis (XRD), room temperature photoluminescence (PL), and scanning electron microscope (SEM). The results show that the dense and uniformed GaN films with highly c-axis preferred orientation are successfully achieved on stainless substrates under optimized deposition temperature of 400°C. In addition, the approximate Ohmic contact behavior between GaN film and stainless steel substrate was clearly demonstrated by the current-voltage (I–V) dependence.