Growth of high material quality InAs/GaSb type-II superlattice for long-wavelength infrared range by molecular beam epitaxy

By optimizing the V/III beam-equivalent pressure ratio, a high-quality InAs/GaSb type-II superlattice material for the long-wavelength infrared (LWIR) range is achieved by molecular beam epitaxy (MBE). High-resolution x-ray diffraction (HRXRD), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectrometer are used to characterize the material growth quality. The results show that the full width at half maximum (FWHM) of the superlattice zero-order diffraction peak, the mismatching of the superlattice zero-order diffraction peak between the substrate diffraction peaks, and the surface roughness get the best results when the beam-equivalent pressure (BEP) ratio reaches the optimal value, which are 28 arcsec, 13 arcsec, and 1.63 Å, respectively. The intensity of the zero-order diffraction peak is strongest at the optimal value. The relative spectral response of the LWIR detector shows that it exhibits a 100% cut-off wavelength of 12.6 μm at 77 K. High-quality epitaxial materials have laid a good foundation for preparing high-performance LWIR detector.     

Different temperature dependence of carrier transport properties between AlxGa1-xN/InyGa1-yN/GaN and AlxGa1-xN/GaN heterostructures

The temperature dependence of carrier transport properties of AlxGa1-xN/InyGa1-yN/GaN and AlxGa1-xN/GaN heterostructures has been investigated.It is shown that the Hall mobility in Al0.25Ga0.75N/In0.03Ga0.97N/GaN heterostructures is higher than that in Al0.25Ga0.75N/GaN heterostructures at temperatures above 500 K,even the mobility in the former is much lower than that in the latter at 300 K.More importantly,the electron sheet density in Al0.25Ga0.75N/In0.03Ga0.97N/GaN heterostructures decreases slightly,whereas the electron sheet density in Al0.25Ga0.75N/GaN heterostructures gradually increases with increasing temperature above 500 K.It is believed that an electron depletion layer is formed due to the negative polarization charges at the InyGa1-yN/GaN heterointerface induced by the compressive strain in the InyGa1-yN channel,which e-ectively suppresses the parallel conductivity originating from the thermal excitation in the underlying GaN layer at high temperatures.     

六元瓜环修饰的花团状铜的催化活性

采用水热法,将六元瓜环(Q[6])分散的五水硫酸铜用抗坏血酸还原后获得了六元瓜环修饰的超微花团状铜(Q[6]-Cu花团).利用X射线粉末衍射(XRD)和扫描电子显微镜(SEM)对产物进行了结构和形貌表征,通过催化氧化染料罗丹明B(Rh B)、结晶紫(CV)、茜素红(AR)和次甲基蓝(MB)考察了产物的催化性能.结果表明,Q[6]-Cu花团直径约为2.0μm.在Q[6]-Cu/H_2O_2体系中,0.08 g/L的Q[6]-Cu在300 min内对染料脱色效率均超过87%.     

1-氮杂环[2.2.2]辛烷的高效合成

将4-（2-羟乙基）哌啶蒸汽在425 ℃下通过CNM-3型固体酸催化剂进行分子内脱水反应,一步合成了目的产物1-氮杂环[2.2.2]辛烷（奎宁环）,4 h内25 g 4-（2-羟乙基）哌啶蒸汽单程收率可达76.8%,最高收率84.3%。 该方法原料易得,适合于奎宁环的工业化制备。     

高质量硼掺杂单晶金刚石同质外延及电学性质研究

突破高质量、高效金刚石掺杂技术是实现高性能金刚石功率电子器件的前提。本文利用微波等离子体化学气相沉积(MPCVD)法,以三甲基硼为掺杂源,制备出表面粗糙度0.35 nm,XRD(004)摇摆曲线半峰全宽28.4 arcsec,拉曼光谱半峰全宽3.05 cm^-1的高质量硼掺杂单晶金刚石。通过改变气体组分中硼元素的含量,实现了10¹⁶~10²⁰ cm^-3的p型金刚石可控掺杂工艺。随后,研究了硼碳比、生长温度、甲烷浓度等工艺条件对p型金刚石电学特性的影响,结果表明:在硼碳比20×10^-6、生长温度1 100 ℃、甲烷浓度8%、腔压160 mbar(1 mbar=100 Pa)时p型金刚石迁移率达到207 cm²/(V·s)。通过加氧生长可以提升硼掺杂金刚石结晶质量,降低杂质散射。当氧气浓度为0.8%时,样品空穴迁移率提升至 614 cm²/(V·s)。     

利用复式晶胞实现二维正方形布拉菲格子光子晶体的完全带隙

利用较为简单的正方形布拉菲格子，采用复式晶胞实现了简单晶胞所不能实现的二维光子晶体的完全带隙，并用优化算法对复式晶胞的结构参数进行了讨论，得到了具有完全的、带隙宽度尽量大的二维光子带隙材料结构- 关键词： 光子晶体 正方形布拉菲格子 复式晶胞 二维完全光子带隙     

Leakage current reduction by thermal oxidation in Ni/Au Schottky contacts on lattice-matched In0.18Al0.82N/GaN heterostructures

By using temperature-dependent current–voltage, variable-frequency capacitance–voltage, and Hall measurements,the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-matched In0.18Al0.82N/GaN heterostructures are investigated. Decrease of the reverse leakage current down to six orders of magnitude is observed after the thermal oxidation of the In0.18Al0.82N/GaN heterostructures at 700oC. It is confirmed that the reverse leakage current is dominated by the Frenkel–Poole emission, and the main origin of the leakage current is the emission of electrons from a trap state near the metal/semiconductor interface into a continuum of electronic states associated with the conductive dislocations in the InxAl1-xN barrier. It is believed that the thermal oxidation results in the formation of a thin oxide layer on the InxAl1-xN surface, which increases the electron emission barrier height.     

GC–MS法快速测定食品接触材料油墨中16种多环芳烃

以正己烷超声提取,弗罗里硅土固相萃取柱净化,以正己烷–二氯甲烷溶液(体积比1∶1)洗脱,用GC–MS联用仪SIM模式外标法定量测定食品接触材料油墨中16种多环芳烃。在优化条件下,16种多环芳烃的浓度在0.1～4.0μg/mL范围内与色谱峰面积呈良好的线性关系,线性相关系数大于0.995,检出限为0.12～3.24 ng/L。加标回收率为77.24%～104.76%,测定结果的相对标准偏差为1.05%～1.69%(n=6)。该方法适用于食品接触材料油墨中PAHs的日常检测。     

海量遥感影像管理与可视化系统的研究与实现

随着遥感技术的飞速发展,产生了海量的遥感影像数据.为了有效管理和利用这些数据,研究设计了海量遥感影像管理与可视化系统.利用基于扩展的对象关系型数据库,对遥感影像进行组织和管理,并针对海量数据的显示效率问题,提出了优化方法,最后给出了系统运行的实例.实践表明,该系统能够较好地满足海量遥感影像数据的高效管理与可视化要求.     

Scattering behaviours to the two-dimensional electron gasinduced by the Al composition fluctuation in AlxGa1-xNbarrier in AlxGa1-xN/GaN heterostructures

<正>This paper reports that cathodoluminescence（CL） measurements have been done to study the alloy fluctuation of the Al_0.3Ga_0.7N layer in Al_0.3Ga_0.7N/GaN heterostructures.The CL images and linescanning results demonstrate the existence of compositional fluctuation of Al in the Al_0.3Ga_0.7N barrier.A model using aδ-shape perturbation Hamilton function has been proposed to simulate the scattering probability of the two dimensional electron gases （2DEG） induced by Al composition fluctuation.Two factors,including conduction band fluctuation and polarization electric field variation,induced by the Al composition fluctuation have been taken into account.The scattering relaxation time induced by both factors has been estimated to be 0.31 ns and 0.0078 ns,respectively,indicating that the variation of the piezoelectric field is dominant in the scattering of the 2DEG induced by Al fluctuation.