Fabrication and photoluminescence of GaN nanowires prepared by ammoniating GaeO3/BN films on Si substrate

GaN nanowires were successfully prepared on Si（111） substrate through ammoniating Ga203/BN films deposited by radio frequency magnetron sputtering system. The synthesized nanowires were confirmed as hexagonal wurtzite GaN by X-ray diffraction, selected-area electron diffraction and Fourier transform infrared spectra. Scanning electron microscopy and transmission electron microscopy revealed that the grown GaN nanowires have a smooth and clean surface with diameters ranging from 40 to 160 nm and lengths typically up to several tens of micrometers. The representative photoluminescence spectrum at room temperature exhibited a strong UV light emission band centered at 363 nm and a relative weak purple light emission peak at 422 nm. The growth mechanism is discussed briefly.     

Mn掺杂GaN纳米条的制备和性质的研究

通过在1000℃下氨化锰掺杂Ga2O3薄膜制备了大量GaMnN纳米条。采用此法得到的剑状Mn掺杂GaN纳米条是六方纤锌矿结构,Mn的原子百分比是5.43%,纳米条的厚度大约为100 nm,宽度为200~400nm。X射线衍射(XRD)、扫描电镜(SEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED)、X射线光电子能谱(XPS)和荧光分光光度计(PL)用于表征所制备纳米条形貌及光学性质。室温下以325 nm波长的光激发样品表面,发现由于Mn的掺杂使GaN的发光峰有较大的红移。最后,简单讨论了GaN纳米条的生长机制。     

In_2O_3纳米材料的制备及其光学特性研究

采用活性炭直接还原In2O3粉末的热蒸发法,制得大量直径约40～300 nm的In2O3纳米线.采用扫描电子显微镜(SEM)、X射线衍射(XRD)、EDS能谱仪和透射电子显微镜(TEM)对其表面形貌、结构和成分进行分析,结果表明所得纳米线为In2O3.用荧光光谱仪研究其发光特性,得知所得产物在室温下存在较强的蓝绿发光和紫外发光现象,同时结合实验条件对合成In2O3纳米线的生长机理和光致发光机制进行初步讨论.     

ZnS和C60纳米线阵列的构筑和表征

以多孔氧化铝为模板,通过水热反应制备出ZnS 和 C₆₀纳米线阵列,分别用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X射线衍射(XRD)、拉曼光谱以及选区电子衍射图谱(SAED)等,对纳米线阵列形貌和化学成分进行表征.结果表明,ZnS 和C₆₀纳米线均为有序阵列.ZnS纳米线为多晶结构,在波长332 nm紫外光激发下, 发射519 nm特征荧光.同时介绍了水热条件下,在多孔氧化铝模板中填充目的产物,以及制备纳米线有序阵列的相关过程.该方法具有一定的普适性.     

9,10-二(3,5-二氟苯乙烯基)蒽有机纳米线的制备与性质表征

利用再沉淀法制备9,10-二(3,5-二氟苯乙烯基)蒽(TFDSA)有机纳米线,并通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和光致发光光谱(PL)表征所制备的纳米线.结果表明:纳米线表面光滑,长度为20~30μm,宽度为400nm,具有较强的绿色荧光发射,发光峰位于538nm处;将单根TFDSA纳米线作为有源波导可在亚微米量级进行光传播.     

热蒸发法制备TeO_2纳米线的生长机理

以金属碲粉为原料,在450℃下采用热蒸发法在镀金玻璃基板上成功合成TeO_2纳米线,利用X射线衍射、扫描电子显微镜、透射电子显微镜对TeO_2纳米线的结构和形貌进行表征,并对其生长机理进行探讨.研究结果表明,具有四方相晶体结构的TeO_2纳米线直径在70~200 nm之间,长度在几百微米至2 mm.通过对不同生长时间所获得产物的形貌观察,对TeO_2纳米线的生长过程进行了分析,推断TeO_2纳米线是通过气-固机制进行生长,镀金薄膜可能只是起到诱导和加速TeO_2纳米线生长的作用.     

Synthesis and Optical Property Study on ZnO Nanostructures Via Vapor Phase Growth

Nanostructural zinc oxide films have been synthesized via vapor phase growth by heating pure zinc powder. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) results showed that four kinds of morphologies ZnO nanostructures namely nanowires, well-aligned nanorods, nanofeathers and hexagonal nanorods were formed and all of wurtzite structural crystals. The results indicated that the temperature and substrate play an important role in the formation of different morphologies of ZnO nanostructures. The photoluminescence (PL) measurement was carried out for the wellaligned nanorods ZnO sample and blue emission peaks at 420 and 444 nm have been observed at room temperature. And the blue emission mechanism is discussed.     

碳热还原制备碳化硅纳米线

以二氧化硅粉和竹炭粉为原料,在无催化剂的条件下,于1 400℃下用碳热还原制备了SiC纳米线.采用X射线衍射(XRD)、扫描电镜(SEM)和能谱(EDS)分析了该纳米线的形貌和化学组成,同时探讨了SiC纳米线的形成机理.结果表明,所制备的纳米线为β-SiC,纳米线直径为100～150 nm,长度可达数毫米.     

花棒状ZnO单晶体的生长与表征

采用表面活性剂协助自组装法合成了花棒状ZnO,利用X射线衍射、扫描电镜、红外光谱和荧光光谱对该化合物的晶体结构、样品形貌、振动光谱以及发射光谱进行了表征.结果表明:ZnO在表面活性剂的存在下,形成纤锌矿型的六方结构,晶体的生长是沿c轴[001]方向定向生长,并且聚集在某一中心的晶核向三维方向定向生长形成花状形貌.该ZnO晶体的晶胞参数为a=0.324 85(6)nm,c=0.520 43(8)nm,γ=120°.在测量波长范围内ZnO的发射光谱在315,400,473和560 nm左右出现荧光,这些发射光谱的波长位置不随激发光波长的增长而变化,而散射光谱峰的波长位置随激发光的波长增加而增加.     

Effect of TMGa flux on GaN films deposited on Ti coated on glass substrates at low temperature

Highly c-axis-oriented GaN films were deposited on Ti coated glass substrates using low temperature electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition system(ECR-PEMOCVD)with trimethyl gallium(TMGa)as gallium source.The influence of TMGa flux on the properties of GaN films were systematically investigated by reflection high energy electron diffraction(RHEED),X-ray diffraction analysis(XRD),atomic force microscopy(AFM)and Raman scattering.The GaN film with small surface roughness and high c-axis preferred orientation was successfully achieved at the optimized TMGa flux of 1.0 sccm.The ohmic contact characteristic between GaN and Ti layer was clearly demonstrated by the near-linear current-voltage(I-V)curve.The GaN/Ti/glass structure has great potential to dramatically improve the scalability and reduce the cost of solid-state lighting light emitting diodes.     

Hydrothermal synthesis and photoluminescence behavior of CeO<Subscript>2</Subscript> nanowires with the aid of surfactant PVP

Well-crystalline CeO₂ nanowires were prepared via a surfactant-assisted hydrothermal process. Reaction temperature and reaction time were changed for the determination of optimal synthesis parameters. The as-obtained products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The results show that single crystal CeO₂ nanowires with high yield and good uniformity can be obtained hydrothermally at 180°C for 12 h with the aid of 2.0 g surfactant (polyvinyl pyrrolidone, PVP). The role of PVP was then discussed and a possible growth mechanism was proposed. Moreover, room temperature photoluminescence (PL) spectra were obtained for these CeO₂ nanowires, which are believed to be related to the abundant defects in these nanostructures.     

钛酸钠纳米线的合成和结构

利用TiO₂粉末和NaOH水溶液在175℃～240℃水热反应得到了具有层状结构的钛酸钠纳米线。研究了原料比例和反应温度的影响。利用X射线粉末衍射、电子显微术和X射线能量色散谱等结构分析手段研究了纳米线的微观结构。观察到纳米线内部存在大量畴界和缺陷。发现上述钛酸钠纳米线的结构与任何已知结构都不相同,初步标定为单斜结构,单胞参数为a=2.15nm, b=0.377nm, c=1.28nm, β=103.5°。进一步用上述纳米线和KOH溶液水热反应合成了钛酸钾(K₂Ti₈O₁₇)纳米线。     

上转换材料复合介孔TiO2晶须的可见光催化性能

用溶胶凝胶法制备上转换发光材料Y3Al5O12:Er。反射光谱、发射光谱表明:Y3Al5O12:Er在480 nm光的激发下,产生2个<387 nm的紫外光发射峰。将上转换材料介孔TiO2晶须复合成可见光催化剂,采用X线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)以及低温N2吸附-脱附(BET)等对催化剂进行表征,通过光催化降解亚甲基蓝(MB),对催化剂的活性进行测试。结果表明:复合上转换材料的介孔TiO2晶须在可见光下能够有效降解MB,10%Y3Al5O12:Er的介孔TiO2晶须的MB降解率为73%。     

Effect of strain on space charge layer in GaN nanowires investigated by in-situ off-axis electron holography

Effect of strain on space charge (SC) layer in nanowires (NWs) has been examined by in situ off-axis electron holography, where GaN NWs attach to an Au electrode inside a transmission electron microscope (TEM). Based on the phase image reconstructed from the complex hologram, the width of SC layer in a strained GaN NW is significantly reduced to about 60 nm, comparing to the 85 nm of the unstrained NW. About 29% reduction of the SC layer in the strained GaN NW resulted from significant decrease of electrons flowed from the GaN into Au. First principle calculations show that the strain reduced bandgap of GaN, narrowing the difference between GaN NW and Au electrode in Fermi level.     

惰性盐辅助法合成氮化镓纳米棒及其场发射性能研究(英文)

以惰性盐为分散剂,通过直接氮化金属镓与氟化钙的混合物,在较低温度下(650℃)大量合成出角面截面型氮化镓纳米棒,大大低于以往文献报道的氮化温度(900℃以上)。通过X射线衍射和电子显微镜等设备表征,可知所制得的产物为六方相氮化镓纳米棒,且纳米线沿着c轴择优生长;每根氮化镓纳米棒都具有菱形或三角形截面。由于本方法的制备温度低,导致了氮化镓纳米棒与硅基片的良好接触。场发射实验表明,该复合系统具有很低的开启电压(5.4V/μm)和阈场(8.4V/μm)。     

在表面活性剂辅助下优质氢氧化钕纳米线的合成和表征

具有50～100nm平均直径和长约10μm的单晶氢氧化钕纳米线,已经在大量的CTAB（十六烷基三甲基溴化铵）阳离子表面活性剂的协助下通过水热法控制纳米结构的演化成功地合成,在表面活化剂CTAB的辅助下,可控制纳米结构的演化．测量方法包括X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）．借助这些手段,可表征产物的特性．     

三氟化钐纳米圆盘的超声合成及表征

室温条件下,采用温和的超声液相沉淀法制备得到了三氟化钐纳米圆盘.产物的晶相、形貌和尺寸分别用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(TEM)进行了表征.结果表明,所得三氟化钐为高纯、结晶度好的六方晶系,纳米圆盘厚度约为50nm,直径为300～500 nm.进一步检测了SmF3:Tb3+纳米圆盘的荧光性质.     

圆锥形图形化蓝宝石衬底对MOCVD生长GaN外延膜的位错密度和应力应变影响

通过金属氧化物化学气相沉积（MOCVD）方法在2．5μm×1．6μm×0．5μm圆锥形图形化蓝宝石衬底（CPSS）和没有图形化平面蓝宝石衬底（uss）上生长GaN外延膜．高分辨率X射线衍射仪（HRXRD）测试结果表明,生长在CPSS上GaN的刃位错的密度比生长在USS上GaN的刃位错密度低得多;从透射电子显微镜（TEM）观察,CPSS可有效地减小GaN外延膜中的线位错密度;拉曼散射谱显示通过CPSS可有效地减小GaN外延膜中的残余应力;比较两种外延膜中的光致发光谱（PL）,能从生长在CPSS上GaN外延膜中观察到强而尖的带边发射．以上结果表明：生长在CPSS上GaN外延膜的质量高于生长在USS上GaN外延膜的质量．     

氧对纳米ZnO薄膜晶体结构和光致发光的影响

ZnO是一种直接带半导体材料，在光电领域中和GaN一样受到关注．ZnO不仅有与GaN相似的晶体结构，而且它的激子结合能高达60meV，是GaN的2．4倍．采用射频(RF)磁控溅射法在n-Si(001)衬底上生长ZnO薄膜，XRD谱测量显示出氧压对ZnO薄膜的晶体结构有显著影响，用波长为325nm的激光激发，观察到在445nm处有一强的光致发光峰，它来自于氧空位浅施主能级上的电子跃迁到价带，分析了发光峰与氧压的关系以及退火对它的影响。     

溶胶—凝胶模板法制备有序Mn3O4纳米线阵列

通过模板法制备的一维金属氧化物纳米结构在材料科学领域具有潜在的应用前景。以醋酸锰为前驱体,利用多孔阳极氧化铝膜(anodic aluminum oxide,AAO)为模板,通过溶胶—凝胶法成功制备出Mn3O4纳米线阵列。利用扫描电子显微镜(SEM)、X射线衍射(XRD)、热重分析技术等手段分析合成条件与产物的结构、形貌之间的关系。结果表明,所得产物为四方尖晶石结构,纳米线直径约80 nm,长度约几微米。通过测试产物的磁滞回线,发现其在常温下呈顺磁性。