ZnO纳米线场效应管的制备及I-V特性研究

采用静电探针和原子力探针技术,将化学气相沉积工艺制备的,长度为30-200μm,直径80-750 nm的单根半导体ZnO纳米线搭接在Au,Zn,Al不同功函的金属隔离沟道两端,构建出了最基本的ZnO纳米线绝缘栅场效应管.研究了沟道类型、纳米线直径、退火温度和外加栅压对ZnO纳米线场效应管I-V特性的影响.利用半导体与金属材料的肖特基接触、欧姆接触的产生机理及电子输运理论,对结果进行了分析和讨论.     

ZnO纳米线场效应管的制备及I-V特性研究

采用静电探针和原子力探针技术,将化学气相沉积工艺制备的,长度为30—200 μm,直径80—750 nm的单根半导体ZnO纳米线搭接在Au,Zn,Al不同功函的金属隔离沟道两端,构建出了最基本的ZnO纳米线绝缘栅场效应管. 研究了沟道类型、纳米线直径、退火温度和外加栅压对ZnO纳米线场效应管I-V特性的影响. 利用半导体与金属材料的肖特基接触、欧姆接触的产生机理及电子输运理论,对结果进行了分析和讨论. 关键词： ZnO纳米线 场效应管 I-V特性')" href="#">I-V特性     

树形结构Si/ZnO纳米线阵列的制备及光学性能

用一种低成本的方法制备出了树形结构Si/ZnO纳米线阵列。首先在室温条件下用金属辅助化学腐蚀法在Si(100)衬底上制备了Si纳米线阵列,Si纳米线的直径尺寸及分布都很均匀,通过改变腐蚀时间,能够得到高度不同的Si纳米线阵列。利用磁控溅射在Si纳米线表面制备一层ZnO薄膜,然后利用水热法在Si纳米线阵列上生长了ZnO纳米线。通过扫描电子显微镜(SEM)、能谱分析仪(EDS)和光致发光(PL)测试对样品进行了表征。通过这种方法制备的Si/ZnO复合结构在太阳能电池、光催化等领域有潜在应用价值。     

铁纳米线磁行为的微磁学模拟与研究

通过微磁学模拟的手段对用电化学沉积法制备出的呈圆柱形的铁纳米线在常温下的磁行为进行了系统的研究,结果表明不同形状参量的铁纳米线都表现出磁各向异性,矫顽力随纳米线直径变化近似呈现平方反比关系,而对每一固定的直径,矫顽力随纳米线长度的增加而增大,最后趋向定值.磁滞回线形状、静态磁矩分布和反转机制等都随纳米线的直径和长度的变化而变化,对相应的规律给出了明确的解释.模拟结果显示实验上尚不能制备出的直径为5nm的纳米线呈现一致反转机理,同时还发现当纳米线过渡为颗粒时表现出更为复杂的性质 关键词： 纳米线 微磁学     

反铁磁TmFeO3中激光诱导的自旋超快重定向

人们在研究半导体碳纳米管和纳米线真正电子器件上作了很多努力，希望制造出可替代传统硅晶体管的场效应管或独立的纳米电子系统，     

有机-ZnO纳米线混合光电二极管特性

采用水热法制备了1维ZnO纳米线,并通过改变ZnO纳米线的取向（横向和竖直）和不同的P型半导体材料,制备了不同的有机-ZnO纳米线混合光电二极管。通过改变光照与非光照的条件下并在光照条件下改变光电二极管与光源的距离,对所制备的光电二极管的相关特性进行研究。结果表明:采用水热技术能够制备高质量的ZnO纳米线;当光电二极管两端通正向电压时,光照时的电流大于非光照时的电流,当通反向电压时,结果则相反;同时,光电流还与光照强度有关,光照强度越大,光电流越大。     

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. 关键词： 场发射 纳米线 取向 非取向     

纳米电子学的最新进展

文章介绍了纳米电子学在自组织生长、器件构造和电学／光学器件应用等方面的最新进展，其中包括：利用流体或极性分子实现了纳米线／管的定向排列；用此方法制成了纳米线逻辑电路和新型纳米线／带薄膜晶体管；研制成功可进行高密度信息存储的单分子层面纳米线交叉电路；进行了半导体CdS纳米线电泵激光和碳纳米管电致发光研究．此外，还对自旋电子学的研究进展进行了简要介绍，对纳米电子学的研究与发展方向提出了建议。     

四方结构GaN纳米线制备、掺杂调控及其场发射性能研究

作为最重要的第三代半导体材料之一,纳米氮化镓(Ga N)也引起了人们的广泛关注与重视.本文采用微波等离子体化学气相沉积(microwave plasma chemical vapor deposition, MPCVD)系统,成功地制备出了四方截面的Ga N纳米线,其纳米线半径为300—500 nm,长度为15—20μm.研究发现,通过调控掺杂Mg的比例,可以实现其截面结构从三方向四方转变.通过进一步地研究Mg掺杂调控其截面结构的物理机制,提出其三方-四方截面结构的转变应该来源于其纳米线的气-液-固(VLS)生长向自催化气-固(VS)生长模式的转变.对所制备的纳米线进行了光致发光(photoluminescence, PL)光谱分析,结果表明四方结构Mg掺杂Ga N纳米线发光峰红移至386 nm.采用所制备的纳米线进行了场发射性能研究,结果表明四方结构Mg掺杂Ga N纳米线开启电场为5.2 V/μm,并能保持较高电流密度,相较于三方结构未掺杂Ga N纳米线场发射性能有一定提高,进而分析掺杂以及形貌结构对Ga N纳米线场发射的影响机制.研究结果不仅给出了一种四方结构Ga N纳米线的制备方法,同时也为纳米线结构调控提出了新的思路与方法,将为新型纳米线器件设计与制作提供了新的技术手段.     

选区外延生长的PbTe-超导杂化纳米线:一个可能实现拓扑量子计算的新体系

半导体-超导体杂化纳米线是用于研究马约拉纳零能模和拓扑量子计算的主要平台之一,而基于Ⅲ-Ⅴ族半导体InAs和InSb的纳米线则是当前此方向研究的主流材料体系.尽管经过多年制备技术的改进和优化,样品中过多的缺陷和杂质仍是阻碍此方向进一步发展的核心问题.近年来,一个新的马约拉纳纳米线候选体系——Ⅳ-Ⅵ族半导体PbTe-超导杂化纳米线吸引了很大关注并获得了快速的研究进展.PbTe的介电常数巨大,且具有晶格匹配的衬底,这些优势使其有潜力突破纳米线样品质量提升的瓶颈,成为马约拉纳零能模的研究和拓扑量子计算实现的理想平台.本文将简单介绍最近几年在PbTe纳米线和PbTe-超导杂化纳米线器件的选区分子束外延生长、输运性质研究方面取得的重要进展,并对这种新的马约拉纳纳米线候选体系的优势、问题及基于其实现拓扑量子计算的前景进行讨论.     

Type II hybrid structures of TiO2 nanorods conjugated with CdS quantum dots: assembly and optical properties

We developed a novel method to assemble TiO₂ nanorods conjugated with CdS quantum dots by L-cysteine molecular linker for type II semiconducting hybrid structure. The XRD patterns indicate that the CdS quantum dots perform the cubic phase structure, and TEM images show that CdS quantum dots are well dispersed on the surfaces of anatase TiO₂ nanorods with little agglomeration. The UV-vis absorption spectra reveal the bandgap alignment in type II configuration between CdS QDs and TiO₂ nanorods.     

Dopant size dependent variable range hopping conduction in polyaniline nanorods

The present work investigates the electrical transport and dielectric relaxation of polyaniline (PAni) nanorods doped with organic camphorsulfonic acid (CSA) and inorganic hydrochloric acid (HCl) synthesized by interfacial polymerization technique. High resolution transmission electron micrographs (HRTEM) depict that initially spherical nuclei directionally grow into nanorods and CSA doped PAni produces more uniform and aligned structures. The electrical transport studies reveal that the CSA doped nanorods follow 1D Mott variable-range hopping (VRH), whereas the HCl doped nanorods exhibit 2D VRH conduction mechanism. The value of interchain charge transfer integral is found to be higher for smaller size HCl doped PAni than that for larger size CSA doped PAni. The resistivity measurements exhibit semiconducting behavior for both organic and inorganic dopants and the resistivity of the CSA doped nanorods is found to be smaller than that of the HCl doped nanorods. The dielectric relaxation studies suggest Debye type relaxation with a single relaxation peak for both the dopants and the relaxation time of the carriers of the CSA doped PAni nanorods is smaller than that of the HCl doped nanorods.     

PLD方法制备的ZnO纳米柱结构及光学特性

采用无催化脉冲激光沉积(PLD)方法,在InP(100)衬底上生长纳米ZnO柱状结构。采用扫描电子显微镜(SEM)、X射线衍射(XRD)以及光致发光(PL)谱等表征手段对ZnO纳米柱的形貌、晶体结构和光学特性进行了观察。SEM图像观察到ZnO纳米柱状结构具有一定的取向性;XRD测试在2θ=34.10°处观测到强的ZnO(002)衍射峰,证实ZnO纳米柱具有较好的c轴择优取向;室温PL谱在379nm处观察到了强的自由激子发射峰(半峰全宽为19nm),未探测到深能级跃迁发射峰,表明生长的纳米ZnO结构具有很高的光学质量。     

Structures of planar defects in ZnO nanobelts and nanowires

Quasi-one-dimensional (1D) nanostructures, such as nanowires, nanobelts and nanorods, are the forefront materials for nanotechnology. To date, such nanostructures have been synthesized for a wide range of semiconductors and oxides, and they are potential building blocks for fabricating numerous nano-scale devices. 1D ZnO nanostructures, due to its unique semiconducting, piezoelectric, and bio-safe properties, have received wide attention. From structure point of view, a common characteristic of ZnO nanostructures is that they are mostly dislocation-free. However, planar and point defects do frequently exist in such nanostructures. The objective of this paper is to present detailed electron microscopy study about the structures of planar defects, such as stacking faults, twins, inversion domain walls that existed in 1D ZnO nanostructures. These planar defects are important for understanding the growth mechanism and relevant physical and possibly chemical properties of 1D ZnO nanostructures.     

Synthesis and physical properties of mixed Co3O4/CoO nanorods by microwave hydrothermal technique

A mixture of crystalline Co₃O₄/CoO nanorods with non-uniform dense distribution has been successfully synthesized by microwave hydrothermal technique. The synthesized nanorods have been characterized by several techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transforms infrared spectroscopy (FT-IR). The results showed that the as synthesized specimens contained mixed crystalline Co₃O₄/CoO nanorods with an average length of around 80 nm and an average diameter of 42 nm. UV–Vis spectrum of the nanorods exhibited a strong UV emission. The band energy gap of the product was 1.79 eV which lies between the energy gap of CoO and that for Co₃O₄. The obtained carrier concentration is of the order 4.32 × 10²⁷ m⁻³ and the dielectric constant is found to be 4.89. The electrical conductivity increases with increasing temperature and behaves as a semiconducting material with an activation energy of a bout 0.26 eV. This makes the as synthesized mixed Co₃O₄/CoO nanorods very useful for supercapacitor devices application. Magnetic hysteresis loops at room temperature of the as synthesized mixed oxides (Co₃O₄/CoO) nanorods exhibit typical soft magnetic behavior.     

Visible fluorescence induced by the metal semiconductor transition in composites of carbon nanotubes with noble metal nanoparticles

We show that single-walled carbon nanotube (SWNT) bundles emit visible fluorescence in the presence of noble metal nanoparticles and nanorods in the solid state. Conductivity measurements with metallic nanotubes, isolated from pristine SWNTs, show that they become semiconducting in the presence of the metal nanoparticles. Nanoparticle binding increases the defects in the nanotube structures which is evident in the Raman spectra. The metal-semiconductor transition removes the nonradiative decay channels of the excited states enabling visible fluorescence. Nanotube structures are imaged using this emission with resolution below the classical limits.     

Preparation and room temperature NO_2-sensing performances of porous silicon/V_2O_5nanorods

In this paper, porous silicon/V₂O₅ nanorod composites are prepared by a heating process of as-sputtered V film on porous silicon (PS) at 600 ℃ for different times (15, 30, and 45 min) in air. The morphologies and crystal structures of the samples are investigated by field emission scanning electron microscope (FESEM), x-ray diffractometer (XRD), x-ray photoelectron spectroscopy (XPS), and Raman spectrum (RS). An improved understanding of the growth process of V₂O₅ nanorods on PS is presented. The gas sensing properties of samples are measured for NO₂ gas of 0.25 ppm～3 ppm at 25 ℃. We investigate the effects of the annealing time on the NO₂-sensing performances of the samples. The sample obtained at 600 ℃ for 30 min exhibits a very strong response and fast response-recovery rate to ppm level NO₂, indicating a p-type semiconducting behavior. The XPS analysis reveals that the heating process for 30 min produces the biggest number of oxygen vacancies in the nanorods, which is highly beneficial to gas sensing. The significant NO₂ sensing performance of the sample obtained at 600 ℃ for 30 min probably is due to the strong amplification effect of the heterojunction between PS and V₂O₅ and a large number of oxygen vacancies in the nanorods.     

Near-Field Optical Identification of Metallic and Semiconducting Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes(SWCNTs),due to their outstanding electrical and optical properties,are expected to have extensive applications,such as in transparent conductive fims and ultra-small field-effect transistors(FETs).However,those applications can only be best realized with pure metallic or pure semiconducting SWCNTs.Hence,identifying and separating metallic from semiconducting SWCNTs in as-grown samples are crucial.In addition,knowledge of the type of an SWCNT is also important for further exploring its new properties in fundamental science.Here we report employing scanning near-field optical microscopy(SNOM) as a direct and simple method to identify metallic and semiconducting SWCNTs on SiO_2/Si substrates.Metallic and semiconducting SWCNTs show distinct near-field optical responses because the metallic tubes support plasmons whereas the semiconducting tubes do not.The reliability of this method is verified using FET testing and Rayleigh scattering spectroscopy.Our result demonstrates that the SNOM technique provides a reliable,simple,noninvasive and in situ method to distinguish between metallic and semiconducting SWCNTs.     

Hybrid bulk heterojunction solar cells based on blends of TiO2 nanorods and P3HT

Over the past decades, organic solar cells based on semiconducting polymers or small molecules have become a promising alternative to traditional inorganic photovoltaic devices. However, to address the intrinsic limitations of organic materials, such as charge separation yield, charge transport and durability, new strategies based on hybrid organic/inorganic materials have been explored. One such approach exploits mesoporous inorganic nanostructures as electron acceptors, which takes advantage of the potential to control the active layer structure and interface morphology through nanoparticle synthesis and processing. In this work, the potential of hybrid photovoltaics will be discussed and illustrated through a recent study of bulk heterojunction systems based on the blend of TiO₂ nanorods with a conjugated polymer. To cite this article: J. Bouclé et al., C. R. Physique 9 (2008).     

Synthesis of Au nanorods via autocatalytic growth of Au seeds formed by sonochemical reduction of Au(I): Relation between formation rate and characteristic of Au nanorods

The sonochemical formation of Au seeds and their autocatalytic growth to Au nanorods were investigated in a one-pot as a function of concentration of HAuCl₄, AgNO₃, and ascorbic acid (AA). The effects of ultrasonic power and irradiation time were also investigated. In addition, the formation rate of Au nanorods was analyzed by monitoring the extinction at 400 nm by UV–Vis spectroscopy and compared with the growth behavior of Au seeds to nanorods. Most of the reaction conditions affected the yield, size, and shape of Au nanorods formed. It was confirmed that the concentration balance between HAuCl₄ and AA was important to proceed the formation of Au seeds and nanorods effectively. The formation rate became faster with increasing AA concentration and dog-bone shaped nanorods were formed at high AA concentration. It was also confirmed a unique phenomenon that the shape of Au nanorods changed even after the completion of the reduction of Au(I) in the case of short-time ultrasonic irradiation for Au seed formation.