KxWO3有序孪晶纳米线的合成和TEM表征

通过简单的实验方法在玻璃衬底上得到了钾钨青铜(KxWO3)纳米线。利用透射电镜选区电子衍射方法结合明场像及高分辨电子显微像分析确定了KxWO3纳米线的结构及生长方向,发现KxWO3纳米线具有有序的单斜超结构,该单斜KxWO3相以[001]m为孪晶轴的120°三次旋转孪晶的形式存在,纳米线的生长方向为[001]m。通过暗场像分析,确定了纳米线是由更小尺度的纳米单元构成的。根据透射电子显微分析结果并结合实验过程,对KxWO3纳米线可能的形成机制进行了讨论。     

氨化Si基Ga2O3/Co薄膜合成GaN纳米线及其表征

采用磁控溅射技术先在Si衬底上制备Ga2O3/Co薄膜,然后在950"C下流动的氨气中进行氨化反应制备GaN纳米棒.应用X射线衍射、扫描电镜、傅里叶红外吸收光谱、选区电子衍射和高分辨透射电子显微镜对样品进行表征.结果表明,采用此方法得到了六方纤锌矿结构的GaN单晶纳米棒.观察发现纳米棒表面光滑.并讨论了GaN纳米棒的生长机制.     

InGaN/GaN多量子阱纳米线发光二极管制备及研究

用SiO2纳米图形层作为模板在以蓝宝石为衬底的n-GaN单晶层上制备了InGaN/GaN多量子阱纳米线,并成功实现了其发光二极管器件(LED).场发射扫描电子显微镜(FESEM)的测量结果表明,InGaN/GaN多量子阱纳米线具有光滑的表面形貌和三角形的剖面结构.室温下阴极射线荧光谱(CL)的测试发现了位于461 nm...     

氨化Si基Ga2O3/Co薄膜合成GaN纳米线及其表征

采用磁控溅射技术先在Si衬底上制备Ga2O3/Co薄膜,然后在950"C下流动的氨气中进行氨化反应制备GaN纳米棒.应用X射线衍射、扫描电镜、傅里叶红外吸收光谱、选区电子衍射和高分辨透射电子显微镜对样品进行表征.结果表明,采用此方法得到了六方纤锌矿结构的GaN单晶纳米棒.观察发现纳米棒表面光滑.并讨论了GaN纳米棒的生长机制.     

Ga-N共掺氧化锌纳米线阵列制备及发光性能研究

采用化学气相沉积法（CVD）以一氧化氮（NO）和氧化镓（Ga2O3）为掺杂源,在c轴取向单晶蓝宝石衬底上外延生长镓氮（Ga-N）共掺氧化锌（ZnO）纳米线阵列。利用SEM, XRD, HRTEM, XPS, PL等测试手段对掺杂后的ZnO纳米线阵列进行结构、成分和光学性能表征。结果表明,Ga-N共掺ZnO纳米线阵列保持六方纤锌矿结构,沿（002）方向择优生长;掺杂元素在样品中均匀分布。随着掺杂浓度增加,纳米线由六棱柱结构转变为尖锥层状结构,长度由2 μm减小到1 μm,锥度增加至0.95;N 1s/Ga 2p/Zn 2p峰结合能向低能态方向移动。PL光谱分析表明,所有样品均出现紫外发光峰和绿光发光峰,不同掺杂浓度的缺陷发光强度不同。     

原位环境透射电镜研究SnO2纳米线作为K-O2电池空气正极的放电行为

本文使用先进的球差校正环境透射电子显微镜(AC-ETEM)与原位电化学测试平台,在环境透射电镜中以SnO₂纳米线作为空气正极,构建起一纳米K-O₂金属空气电池,原位观测该电池在氧还原反应(ORR)过程中的微观变化行为。实验结果表明:在ORR过程中,SnO₂纳米线首先转化为Sn单质颗粒与K₂O;因纳米尺度的Sn单质颗粒具有优异的催化活性,在O₂氛围中纳米线的表面生成了大量的KO₂。但由于KO₂不能稳定存在,会迅速分解成K₂O₂并释放O₂,导致材料发生巨大的体积膨胀。相关实验结果为宏观K-O₂电池的设计与改性提供了直观的实验证据。     

砷化镓纳米线在非晶玻璃衬底生长和特性研究

The growth of GaAs nanowires directly on fused quartz substrates using molecular beam epitaxy via a vapor-liquid-solid mechanism with gold as catalyst is reported. Unlike conventional Au-catalyst MBE growth of nanowires （NWs） on GaAs substrates, zinc blende is found to be the dominant crystal structure for NWs grown on fused-quartz substrates by MBE. Further transmission electron microscopy measurements show that the prepared ZB NWs have the growth direction of [112] and lamellar { 111 } twins extend through the length of NWs. Although there are longitudinal planar defects that extend through NWs, the narrow full width at half maximum of PL implies high crystal quality of NWs grown on fused-quartz substrates.     

HVPE生长GaN厚膜的结构和光学性能

采用自制的立式HVPE设备,在GaN/蓝宝石复合衬底上生长了GaN厚外延膜,利用AFM,SEM,XRD,RBS/Channeling,CL,PL以及XPS等技术分析了厚膜的结构和光学性能.结果表明,外延层表面具有台阶结构,接近以层流生长方式二维生长,一些六角形的坑出现在膜表面,坑区具有很强的发光.腐蚀试验显示EPD仅8×106 cm-2;XRD和RBS/channeling表明GaN膜具有较好的晶体质量;PL结果也证明外延层具有高的质量,出现了尖锐的带边峰,半高宽仅67meV,同时出现了黄带和红外带,这些带的出现可能是由本征缺陷和C,O等杂质引起的.     

HVPE生长GaN厚膜的结构和光学性能

采用自制的立式HVPE设备,在GaN/蓝宝石复合衬底上生长了GaN厚外延膜,利用AFM,SEM,XRD,RBS/Channeling,CL,PL以及XPS等技术分析了厚膜的结构和光学性能.结果表明,外延层表面具有台阶结构,接近以层流生长方式二维生长,一些六角形的坑出现在膜表面,坑区具有很强的发光.腐蚀试验显示EPD仅8×106 cm-2;XRD和RBS/channeling表明GaN膜具有较好的晶体质量;PL结果也证明外延层具有高的质量,出现了尖锐的带边峰,半高宽仅67meV,同时出现了黄带和红外带,这些带的出现可能是由本征缺陷和C,O等杂质引起的.     

Sn@MnOX核壳结构微/纳米线的合成和结构表征

本文合成了一种新型结构的微/纳米线。利用光学显微镜、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和能量色散X射线谱(EDS)对所合成微/纳米线的形态、组成和微观结构进行研究。结果显示β-Sn微/纳米线作为"核",超薄非晶态MnO_X纳米片作为"壳"层,完全把β-Sn包裹住,形成Sn@MnO_X微/纳米线异质结构。     

Si衬底GaN基多量子阱外延材料的TEM研究

本文采用高分辨透射电子显微技术对在Si衬底生长的GaN基多量子阱外延材料的位错特征、外延层与衬底的晶体取向关系及界面的结晶形态等微观结构进行了分析和研究.结果表明:Si衬底生长的GaN与衬底有一定的取向关系;材料在MQW附近的穿透位错密度达108 cm-2量级,且多数为刃型位错;样品A的多量子阱下方可见平行于界面方向的...     

Iron and manganese doped zinc-blende GaN

The electronic structure of Mn and Fe doping impurities in zinc-blende gallium nitride (c-GaN) crystal lattice have been investigated by the LMTO-TB method. The calculations used the 128 site supercells (64 atoms and 64 empty spheres with an impurity at the origin) with Mn and Fe atoms replacing ions in cation and anion sublattices. It is shown that Mn and Fe ions stay magnetic for all types of substitutions in c-GaN crystal lattice. Fe magnetic moment was found to be 3.5μ_B and 1.0μ_B for cation and anion substitutions, respectively. Similar data for Mn, magnetic moments are 3.3μ_B and 1.9μ_B. The moments are highly localized, though some weak polarization is seen at the closest atoms to the impurity. The total energies for supercells with and without magnetic impurities are used to determine the most probable single substitutional sites for Fe and Mn in c-GaN. The energies of magnetic electrons levels relative to the valence and conduction bands of the host crystal are analyzed by making use of the total and partial densities of states. The results show that combination of optoelectronic and magnetic properties may well be possible for c-GaN iron and Mn doped systems.     

Exciton states in wurtzite and zinc-blende InGaN/GaN coupled quantum dots

Based on the effective-mass approximation, exciton states in wurtzite (WZ) and zinc-blende (ZB) InGaN/GaN coupled quantum dots (QDs) are studied by means of a variational method. Numerical results show clearly that both the sizes and In content of QDs have a significant influence on exciton states in WZ and ZB InGaN/GaN coupled QDs. Moreover, the ground-state exciton binding energy decreases when the interdot barrier layer thickness increases in the WZ InGaN/GaN coupled QDs. However, the ground-state exciton binding energy has a minimum if the interdot barrier layer thickness increases in the ZB InGaN/GaN coupled QDs.     

Property comparison of polarons in zinc-blende and wurtzite GaN/AlN quantum wells

The properties of polarons in zinc-blende and wurtzite GaN/AlN quantum wells with Fr(o|¨)hlich interaction Hamiltonians are compared in detail.The energy shifts of polarons at ground state due to the interface(IF), confined(CO) and half-space phonon modes are calculated by a finite-difference computation combined with a modified LLP variational method.It is found that the two Fr(o|¨)hlich interaction Hamiltonians are consistent with each other when the anisotropic effect from the z-direction and the x-y plane is neglected.The influence of the anisotropy on the polaron energy shifts due to the IF phonon modes for a smaller well width or due to the CO phonon modes for a moderate well width is obvious.In addition,the built-in electric field has a remarkable effect on the polaron energy shifts contributed by the various phonon modes.     

Property comparison of polarons in zinc-blende and wurtzite GaN/AlN quantum wells

本文详细比较闪锌矿和纤锌矿GaN/AlN量子阱中Fr?hlich电声子相互作用哈密顿量及极化子性质。采用LLP变分方法计算由界面、局域和半空间声子模导致的基态极化子能移。结果表明,若忽略z方向和x-y平面之间异性的影响,闪锌矿和纤锌矿哈密顿量是一致的。各向异性在窄阱情形对界面声子能移的影响较为明显,而在略宽阱时对局域声子能移影响明显。此外,内建电场对各支光学声子引起的能移的影响较大。     

Property comparison of polarons in zinc-blende and wurtzite GaN/AIN quantum wells

The properties ofpolarons in zinc-blende and wurtzite GaN/AlN quantum wells with Fr(o)hlich interaction Hamiltonians are compared in detail.The energy shifts of polarons at ground state due to the interface (IF),confined (CO) and half-space phonon modes are calculated by a finite-difference computation combined with a modified LLP variational method.It is found that the two Fr(o)hlich interaction Hamiltonians are consistent with each other when the anisotropic effect from the z-direction and the x-y plane is neglected.The influence of the anisotropy on the polaron energy shifts due to the IF phonon modes for a smaller well width or due to the CO phonon modes for a moderate well width is obvious.In addition,the built-in electric field has a remarkable effect on the polaron energy shifts contributed by the various phonon modes.     

氨化Ga2O3/Mg薄膜制备簇状GaN纳米线

通过在1050°C时氨化Ga2O3/Mg薄膜制备出簇状GaN纳米线。用X射线衍射(XRD),傅里叶红外吸收光谱(FTIR)扫描电子显微镜(SEM)和高分辨电子显微镜(HRTEM)对样品进行测试分析。结果表明,GaN纳米线为六万纤锌矿结构单晶相并且成族生长,直径在200～500nm米左右,其长度可达5～10μm。几乎所有纳米线的直径均有逐渐缩小的趋势。对Mg膜的作用进行了初步的分析。     

硫化铅超细纳米带和纳米线的TEM表征

本文报道了碳化铅越细纳米带和纳米线的电镜研究结果。纳米带宽小于20nm，纳米线直径约30nm，轴向生长方向均为[110]方向。纳米带晶格完整，少有缺陷，而在纳米线中观察到∑17、∑5的[001]领侧晶界和∑17[001]对称倾转晶界，倾侧晶界由一晶粒的[410]或[210]晶面族与另一晶粒的[200]晶面族相互碰撞而形成；对称倾转晶界由两晶粒的[410]晶面族相互碰撞而形成。