取向和非取向In2O3纳米线的场发射研究

用自制的设备制备了取向和无取向氧化铟纳米线,并研究了In2O3纳米线的场发射性质,发现取向纳米线比非取向纳米线有着更好的场发射特性.取向纳米线的开启和阈值场强明显低于非取向纳米线,这可能是由于取向纳米线之间的场屏蔽效应较弱以及取向纳米线有较多的顶部发射端的缘故.     

电化学沉积Fe单晶纳米线生长中的取向控制

利用电化学沉积方法，发现了一种能够动态地控制铁纳米线生长方向的沉积方法，利用该方法沉积了包括［110］取向，［200］取向及非晶态三种结构和取向的一维Fe纳米线阵列.对于三种纳米线阵列，测量了它们的磁特性，分析发现具有[200]择优取向纳米线阵列的方形度，各向异性特性和矫顽力都比[110]取向阵列有很大的改善. 关键词： 磁性纳米线 电化学沉积 取向控制     

氧化锌纳米棒场发射性能研究

采用简单物理气相沉积法制备出取向和非取向的氧化锌纳米棒，他们的场致电子发射性能测量结果表明，ZnO纳米棒具有较好的场发射性能，但是高度取向的ZnO纳米棒阵列并不利于获得高的场致电子发射电流密度.这可能是由于高密度ZnO纳米棒之间具有较高的屏蔽效应，降低了ZnO纳米棒阵列的场放大因子，从而影响了其场发射性能.相反，非取向ZnO纳米棒由于相互之间的屏蔽效应比较弱，而且表面存在容易成为发射中心的微小突起，表现出较好的场发射效果.这些结果不仅有助于加深我们对准一维纳米材料场致电子发射性能的理解，也为未来场发射电子器件的实际应用提供了可靠的依据. 关键词： 氧化锌 场发射 非取向     

合成温度和N2/O2流量比对碳纤维衬底上生长的SnO2纳米线形貌及场发射性能影响

采用化学气相沉积法系统研究了合成温度和N₂/O₂流量对生长在碳纤维衬底上的SnO₂纳米线形貌及场发射性能的影响规律. 利用扫描电镜(SEM)、透射电镜(TEM), X射线衍射(XRD)及能谱仪(EDS)对产物细致表征, 结果表明, SnO₂纳米线长径比随反应温度的升高而增大; 随N₂/O₂流量比值的增大先增大后变小, 场发射测试表明, 合成温度780 ℃, N₂/O₂流量比为300 : 3 时SnO₂纳米线阵列具有最佳的场发射性能, 开启电场为1.03 V/μm, 场强增加到1.68 V/μm时, 发射电流密度达0.66 mA/cm², 亮度约2300 cd/m².     

K3C60在200K附近的取向相变机理

研究了K₃C₆₀单晶薄膜在200K附近的导带结构.样品温度为190K时,同步辐射角分辨光电子谱能够观察到[111]方向有规律的能带色散.而在220K附近色散不存在.这一实验结果与K₃C₆₀在200K存在取向相变相符合.用反铁磁Ising模型对实验结果进行了分析.结果表明,K₃C₆₀在200K的相变是由低温下的一维无序取向结构转变为200K以上的双取向结构畴与无序分子(约占40 关键词： 3C₆₀')" href="#">K₃C₆₀ 取向相变机理     

外电场辅助化学气相沉积方法制备网格状β-Ga2O3纳米线及其特性研究

利用外电场辅助化学气相沉积（CVD）方法，在蓝宝石衬底上制备出了由三组生长方向构成的网格状β-Ga₂O₃纳米线.研究了不同外加电压大小对β-Ga₂O₃纳米线表面形貌、晶体结构以及光学特性的影响.结果表明：外加电压的大小对样品的表面形貌有着非常大的影响，有外加电场作用时生长的β-Ga₂O₃纳米线取向性开始变好，只出现了由三组不同生长方向构成的网格状β-Ga₂O₃纳米线；并且随着外加电压的增加，纳米线分布变得更加密集、长度明显增长.此外，采用这种外电场辅助的CVD方法可以明显改善样品的结晶和光学质量.     

N i50.5Mn24Ga25.5取向晶体相变应变性能的研究

采用区熔法制备了Ni505_50.5Mn24₂₄Ga255_25.5取向晶体，在底部、中部和顶部各切取一块样品进行相变应变测试.在中部样品中获得了高达14%的相变应变，应变随加热冷却循环次数的增加而逐步降低，第9次和第10次相变时应变为08%.在底部和顶部样品中，降温过程的应变随温度的变化呈现先收缩后膨胀或先膨胀后收缩的现象，我们认为这是由于样品中高度择优取向的马氏体变体竞争的结果所致. 关键词： NiMnGa 取向晶体 相变应变     

控制双激光脉冲的宽度提高N2分子的取向

提出了通过控制双激光脉冲宽度的方法来提高N₂分子取向程度. 利用数值方法求解了N₂分子刚性转子模型在双激光脉冲作用下的薛定谔方程，计算了双原子分子N₂在总强度固定的两束激光脉冲作用下，不同脉冲宽度对于N₂分子取向的影响. 研究结果表明，通过调整两束激光脉冲的宽度，选择合适的延迟时间能够有效提高N₂分子的取向程度. 关键词： 双激光脉冲 分子取向 脉冲宽度     

化合物HoMn6Sn6的磁晶各向异性及自旋重取向相变研究

采用交换相互作用的分子场理论模型对金属间化合物HoMn₆Sn₆的自旋重取向相变进行了研究. 从理论上计算了HoMn₆Sn₆的易磁化方向以及Ho和Mn离子磁矩与c轴夹角随温度的变化. 基于单离子模型计算了Ho离子的一阶和二阶磁晶各向异性常数K_1R和K_2R随温度的变化. 研究表明，为了很好描述该化合物的自旋重取向相变，必须考虑Ho离子的四阶晶场项及相应的二阶磁晶各向异性常数K_2R，K_2R与K_1R和Mn离子磁晶各向异性常数K_1t之间的相互竞争是导致HoMn₆Sn₆自旋重取向相变的重要因素. 关键词： 稀土-过渡族金属间化合物 自旋重取向 磁晶各向异性     

高压低温下固体C60中的取向有序态及再取向的弛豫行为

通过构造C₆₀分子间的相互作用，研究了高压下及玻璃化转变温度附近固体C₆₀的取向状态占有概率分布及再取向的弛豫行为，所得结论均能较好地解释热导率实验中的异常现象. 关键词：     

Tunable growth of (GaxIn1−x)2O3 nanowires by water vapor

The tunable growth of In-doped Ga₂O₃ (Ga₂O₃:In) and Ga-doped In₂O₃ (In₂O₃:Ga) nanowires (NWs) on Au-coated Si substrates was achieved by modulating the amount of water vapor in flowing Ar at 700–750 °C via carbothermal reduction of Ga₂O₃/In₂O₃ powders with a fixed weight ratio. In Ar, only the Ga₂O₃:In NWs were grown, while in wet Ar the In₂O₃:Ga NWs were synthesized instead. The Ga concentration in In₂O₃ NWs decreased with the increment of water vapor in flowing Ar. The growth of both Ga₂O₃:In and In₂O₃:Ga NWs followed the vapor–liquid–solid process. The In and Ga doping induced a redshift and a blueshift in the optical bandgaps of Ga₂O₃ NWs and In₂O₃ NWs, respectively. The growth mechanisms and optical properties of Ga₂O₃:In and In₂O₃:Ga NWs were discussed.     

Control synthesis of octahedral In2O3 crystals,belts, and nanowires

Octahedral In₂O₃ crystals were synthesized by evaporation of a mixture of In₂O₃ and graphite in a horizontal double-tube system. By adjusting the experimental conditions, In₂O₃ nanowires and nanobelts were also obtained. The microstructures of the resultant In₂O₃ materials were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), X-ray diffraction. In addition, the growth mechanism of the octahedral In₂O₃ crystals was discussed in detail.     

Indium oxide nanostructures

In this report we review the growth of indium oxide (In₂O₃) nanostructures, including octahedral nanocrystals (NCs), nanobelts (NBs), nanosheets (NSs), and nanowires (NWs), by hot-wall chemical vapor deposition (HW-CVD). This system is highly controllable, allowing the user to easily access different growth regimes – each corresponding to the growth of a different nanostructure – by changing growth variables of the HW-CVD system. Hot-wall CVD produces crystalline nanostructures; here we present a survey of microstructural characterizations of the four types of In₂O₃ nanostructures using transmission- and scanning-electron microscopy. Interestingly, the In₂O₃ nanostructures have different preferred growth directions: NCs have (111) faces, NBs are predominantly (200), and NWs are predominantly (110). We end the review by discussing the current shortcomings of HW-CVD growth of In₂O₃ nanostructures. PACS 61.46.-w; 61.82.Rx; 73.31.Hb; 81.02.-b     

Synthesis,structural and ellipsometric evaluation of oxygen-deficient and nearly stoichiometric zinc oxide and indium oxide nanowires/nanoparticles

Oxygen-deficient (OD) and nearly stoichiometric (NST) ZnO and In₂O₃ nanowires/nanoparticles were synthesized by chemical vapor deposition on Au-coated silicon substrates. The OD ZnO and OD In₂O₃ nanowires were synthesized at 750 and 950°C, respectively, using Ar flow at ambient pressure. A mixture of flowing Ar and O₂ was used for synthesizing NST ZnO nanowires and NST In₂O₃ nanoparticles. Growth of OD ZnO nanowires and NST In₂O₃ nanoparticles was found to be via a vapor–solid (VS) mechanism and the growth of NST ZnO nanowires was via a vapor–liquid–solid mechanism (VLS). However, it was uncertain whether the growth of OD In₂O₃ nanowires was via a VS or VLS mechanism. The optical constants, thickness and surface roughness of the prepared nanostructured films were determined by spectroscopic ellipsometry measurements. A three-layered model was used to fit the calculated data to the experimental ellipsometric spectra. The refractive index of OD ZnO, NST ZnO nanowires and NST In₂O₃ nanoparticles films displayed normal dispersion behavior. The calculated optical band gap values for OD ZnO, NST ZnO, OD In₂O₃ nanowires and NST In₂O₃ nanoparticles films were 3.03, 3.55, 2.81 and 3.52?eV, respectively.     

Synthesis of In-doped Ga2O3 zigzag-shaped nanowires and optical properties

In-doped Ga₂O₃ zigzag-shaped nanowires and undoped Ga₂O₃ nanowires have been synthesized on Si substrate by thermal evaporation of mixed powders of Ga, In₂O₃ and graphite at 1000 °C without using any catalyst via a vapor-solid growth mechanism. The morphologies and microstructures of the products were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and photoluminescence spectroscopy (PL). The nanowires range from 100 nm to several hundreds of nanometers in diameter and several tens of micrometers in length. A broad emission band from 400 to 700 nm is obtained in the PL spectrum of these nanowires at room temperature. There are two blue-emission peaks centering at 450 and 500 nm, which originate from the oxygen vacancies, gallium vacancies and gallium-oxygen vacancy pairs.     

Characterization of interface between CuInSe2 and In2O3

CuInSe₂/In₂O₃ structures were formed by depositing CuInSe₂ films by stepwise flash evaporation onto In₂O₃ films, which were grown by DC reactive sputtering of In target in presence of (Ar+O₂) gas mixture. Phase purity of the CuInSe₂ and In₂O₃ films was confirmed by Transmission Electron Microscopy (TEM) studies. X-ray diffraction (XRD) results on CuInSe₂/In₂O₃/glass structures showed sharp peaks corresponding to (112) plane of CuInSe₂ and (222) plane of In₂O_3. Rutherford Backscattering Spectrometry (RBS) investigations were carried out on CuInSe₂/In₂O₃/Si structures in order to characterize the interface between In₂O₃ and CuInSe₂. The results show that the CuInSe₂ films were near stoichoimetric and In₂O₃ films had oxygen deficient composition. CuInSe₂/In₂O₃ interface was found to include a ∼20 nm thick region consisting of copper, indium and oxygen. Also, the In₂O₃/Si interface showed the formation of ∼20 nm thick region consisting of silicon, indium and oxygen. The results are explained on the basis of diffusion/reaction taking place at the respective interfaces.     

In2O3纳米微粒非线性光学特性

用Z扫描技术研究了In₂O₃纳米微粒有机溶胶和水溶胶的三阶非线性光学特性,发现表面修饰能明显提高In₂O₃纳米微粒的非线性响应.讨论了表面偶极效应对In₂O₃纳米微粒非线性的影响. 关键词：     

Synthesis and characterization of Zn3P2/ZnS core/shell nanowires

Fully-surrounded Zn₃P₂/ZnS core/shell nanowires (NWs) were synthesized for the first time via a two-step method: a catalyst free chemical vapor deposition followed by a low-pressure vulcanization process. Field emission scanning electron microscopy, high-resolution transmission electron microscopy, and high-angle angular dark field scanning transmission electron microscopy were used to characterize the morphologies, crystal structure, and element composition of the core/shell NWs. The band structure analysis demonstrates that the Zn₃P₂/ZnS core-shell NW type-II heterostructures have bright potential in photovoltaic nanodevice applications. The core/shell NW growth method used here can be extended to other material system.     

Co-doped In2O3 thin films: Room temperature ferromagnets

Laser-ablated Co-doped In₂O₃ thin films were fabricated under various growth conditions on R-cut Al₂O₃ and MgO substrates. All Co:In₂O₃ films are well-crystallized, single phase, and room temperature ferromagnetic. Co atoms were well substituted for In atoms, and their distribution is greatly uniform over the whole thickness of the films. Films grown at 550 °C showed the largest magnetic moment of about 0.5 μ_B/Co, while films grown at higher temperatures have magnetic moments of one order smaller. The observed ferromagnetism above room temperature in Co:In₂O₃ thin films has confirmed that doping few percent of magnetic elements such as Co into In₂O₃ could result in a promising magnetic material.     

Enhanced fibroblast cell adhesion on Al/Al2O3 nanowires

Biological cells stick together via transmembrane proteins, which are linked to receptor molecules of the extracellular matrix (ECM). This specific biochemical adhesion plays a leading role in many cellular processes, among them cell differentiation, morphogenesis, and wound healing. Various medical applications require endogen cells to bind to an exogene substrate as in the case of an implant. Coatings with proteins that naturally belong to the ECM are known to enhance the cell adhesion. However, the choice of inorganic materials, which promote cell adhesion, is limited. Here, we report on a new engineered surface composed of Al/Al₂O₃ bi-phasic nanowires (NWs), which promotes the adhesion of fibroblast cells. Fibroblasts grow well on this inorganic layer and keep proliferating. Using the cell monolayer rheology (CMR) technique, we show that the adhesion of fibroblasts on Al/Al₂O₃ NWs is comparable to fibronectin coated surfaces. To our knowledge, this is one of the strongest cell adhesions on an inorganic surface, which has been reported on so far, since it compares to bio-organic layers such as fibronectin.