Activation of Mg-doped P-GaN by using two-step annealing

One- and two-step rapid thermal annealing (RTA) for activating Mg-doped p-type GaN films had been performed to compare with conventional furnace annealing (CFA). The two-step annealing process consists of two annealing steps: the first step is performed at 750 °C for 1 min and the second step is performed at 600 °C for 5 min in pure O₂ or air ambient. It is found that the samples annealed in air ambient exhibit poor electrical properties as compared to those annealed in pure O₂. Compared to one-step RTA annealing and CFA annealing, the samples with two-step annealing exhibit higher hole concentration and lower resistivity. This means that the two-step annealing is a powerful method to enhance the electrical performance of Mg-doped p-type GaN films. Similar results were also evidenced by photoluminescence (PL) measurement. Possible mechanism was confirmed by secondary ion mass spectrometry analysis.     

ZnO电子结构和p型传导特性的第一性原理研究

基于密度泛函理论(DFT)框架下的第一性原理平面波超软赝势方法(USPP)，对不同掺杂情况的ZnO晶体几何结构分别进行了优化计算，从理论上给出了ZnO的晶胞参数，得到了ZnO的总体态密度(TDOS)和氮原子2p态的分波态密度(PDOS).计算结果表明：原胞体积随着掺杂比例的提高而逐渐减小；将氮铝按照2∶1的原子比例共掺可以使氮的掺杂浓度比只掺杂氮时明显提高，且随着铝在锌靶中掺入比例的增加，载流子迁移率提高，浓度增大，使得p型ZnO电导率提高，传导特性增强. 关键词： 共掺 p型传导 态密度 第一性原理     

p型ZnO薄膜的制备及特性

采用射频磁控溅射在Si片上制备ZnO薄膜，通过离子注入对样品进行N掺杂，在不同温度下进行退火并实现了p型转变.用扫描电子显微镜、X射线衍射和Hall测量对薄膜进行了表征，结果表明薄膜具有良好的表面形貌和高度c轴择优取向，退火后p型ZnO薄膜的最高载流子浓度和最低电阻率分别为1.68×10¹⁶cm^-3和41.5Ω·cm.讨论并分析了退火温度和时间对ZnO薄膜p型转变的影响.     

Characterization of nitrogen-doped ZnO thin films grown by plasma-assisted pulsed laser deposition on sapphire substrates

The crystalline, optical and electrical properties of N-doped ZnO thin films were measured using X-ray diffraction, photoluminescence and Hall effect apparatus, respectively. The samples were grown using pulsed laser deposition on sapphire substrates coated priorly with ZnO buffer layers. For the purpose of acceptor doping, an electron cyclotron resonance (ECR) plasma source operated as a low-energy ion source was used for nitrogen incorporation in the samples. The X-ray diffraction analyses indicated some deterioration of the ZnO thin film with nitrogen incorporation. Temperature-dependent Van der Pauw measurements showed consistent p-type behavior over the measured temperature range of 200–450 K, with typical room temperature hole concentrations and mobilities of 5×10¹⁵ cm⁻³ and 7 cm²/V s, respectively. Low temperature photoluminescence spectra consisted of a broad emission band centered around 3.2 eV. This emission is characterized by the absence of the green deep-defect band and the presence of a band around 3.32 eV.     

化学气相沉积法中SnO2一维纳米结构的控制生长

以Sn和SnO为源材料，化学气相沉积法中通过控制反应物配比及载气中的氧含量等宏观实验条件，实现了SnO₂一维纳米结构的控制生长，成功获得各种不同横向尺度的SnO₂纳米线、纳米带以及直径连续变化的针状纳米结构. 通过扫描电子显微镜、X射线衍射仪对不同实验条件下所制备的样品进行形貌和晶格结构表征，认为高温生长点附近锡与氧的相对含量是控制SnO₂一维纳米结构生长的关键因素；并在此基础上对SnO₂一维纳米结构的生长机理进行了深入的讨论.     

NH3气氛处理制备p型ZnO薄膜及性能表征

采用NH₃气氛处理直流/射频共溅射方法制得的ZnO：Al薄膜，从而获得Al+N共掺p型ZnO薄膜.XRD，场发射扫描电子显微镜测试及Hall效应测试发现，处理温度对ZnO薄膜的结构和电学性能具有较大的影响，其中处理温度为700℃时，薄膜具有较好的c轴择优取向，并且薄膜表面平整，结构紧密，晶粒大小均匀，无明显空洞和裂缝，具有良好的表面质量，晶粒尺寸约为40—60nm，薄膜的导电类型由n型转变为p型.     

Structures and Properties of Supported Polyimide/SnO2 Hybrid Membranes

A series of polyimide/SnO2 hybrid membranes supported on TiO2/kieselguhr-mullite were prepared from polyimide with a large amount of carboxyl and SnO2 sol via a sol-gel process. The SnO2 phase chemically linked with the polyimide through the pendant carboxyl along the polyimide. The hybrid membranes were highly homogeneous, and when the SnO2 contents reached 15wt% the SnO2 phase was observed as particles with a diameter of 5 nm dispersed in the hybrid membranes . The cross-linking between the SnO2 phase and polyimide effectively enhanced the glass temperature of the hybrid films. With the increasing of the SnO2 contents, the pore sizes of the membranes decreased, and their pore sizes were mainly focused on 3.8, 3.1, 2.8 and 2.4 nm. The hybrid membranes showed higher permeability for H2, CO2, CO and H2O when compared to the pure polyimide. The separation factors of the polyimide/SnO2 hybrid membranes with 15wt% SnO2 content for H2/N2, CO2/N2, CO/N2 and H2O/N2 were 54.1, 30.2, 35.9 and 40.1, respectively.     

不同形态SnO2纳米晶的制备

In this paper, we report our research on morphologically selective synthesis of nanocrystalline SnO2 by the combination of hydrothermal preparation and calcinated process. We firstly prepared SnO2 nanocrystals by the hydrothermal method at 140 ℃ for 3 h, using SnCI4 as the reactant. With the initial pH of 1.8 or 1.34, we prepared uniform and well-dispersed SnO2(tetragonal) nanocrystals, with similar size of about 3 nm, as determined by TEM. However, after being calcinated at 500 ℃ for 2 h, specimen 1 prepared at pH＝1.8 showed the rod-like shape with an average size of 5 nm×20 nm, while the other one(specimen 2)prepaed at pH＝1.34 showed a granular shape with an average size of 10 nm. XRD experiments showed that specimen 1 had a new diffraction peak after calcination, which was contributed by the (023) face of orthorhombic SnO2. The experiment results indicated that the morpholgy of SnO2 nanocrystals after calcination was closely related to the initial acidity of the reaction solution, possibly due to the difference in surface properties, e.g. the difference in crystalline faces exposed to the surface of particals, under different hydrothermal conditions.     

Electrical and Raman properties of p-type and n-type modified graphene by inorganic quantum dot and organic molecule modification

We obtained n-type and p-type modified graphene by mixing quantum dots and depositing electron-acceptor molecules on the surface of graphene, respectively. The electrical and optical properties of these two types of samples were measured. For n-type modified graphene, the electrons were transferred from quantum dots to graphene. The resistance of these quantum dots in modified n-type graphene is significantly smaller than that of pristine graphene. For p-type graphene, modified by electron-acceptor organic ...     

Carbon‐Coated Hierarchical SnO2 Hollow Spheres for Lithium Ion Batteries

Hierarchical SnO₂ hollow spheres self‐assembled from nanosheets were prepared with and without carbon coating. The combination of nanosized architecture, hollow structure, and a conductive carbon layer endows the SnO₂‐based anode with improved specific capacity and cycling stability, making it more promising for use in lithium ion batteries.