电沉积氧化锌纳米柱的带隙和近带边发射蓝移

用电化学沉积方法制备了ZnO纳米柱阵列。在Zn(NO₃)₂基础电解液中加入新电解质并引入NH₄NO₃ 和Ga(NO₃)₃,实现了对ZnO纳米柱阵列的带隙、近带边发射、斯托克斯位移、直径、密度等物理性质的设计和裁剪。可在63~77 nm操控纳米柱的直径。增加电解液中的Ga(NO₃)₃浓度,阵列的密度可降低到7.0×10⁹ /cm²。新加入电解液中的盐类使ZnO纳米柱的带隙蓝移~50 meV并使光致发光图谱中的近带边发射蓝移53~73 meV以及斯托克斯位移蓝移23 meV,表明可对其非辐射复合进行抑制设计和裁剪。     

氧化锌纳米柱阵列的水热合成及其性能

用水热法在溶解有Zn(CH3COO)2与C6H12N4的溶液中添加NH4NO3与Al(NO3)3制备了ZnO纳米柱阵列。结果表明,添加在溶液中的NH4NO3降低了制备出的ZnO纳米柱的缺陷态密度,减小了其内部的非辐射复合中心的密度。ZnO纳米柱内部的非辐射复合的减弱导致其斯托克斯位移降低49%,从而得到高质量的ZnO纳米柱阵列。控制NH4NO3与Al(NO3)3在溶液中的添加可在3.36-3.57 e V范围内调控ZnO纳米柱的光学带隙宽度。Al的引入使ZnO纳米柱内部载流子的浓度提高,在布尔斯坦-莫斯效应作用下纳米柱的光学带隙蓝移至3.56-3.57 e V。     

退火温度对ZnO量子点光电性能影响的研究

采用溶胶-凝胶方法,利用醋酸锌(Zn-(CH_3COO)_2·2H_2O)和氢氧化锂(LiOH·H_2O)制备氧化锌(ZnO)量子点(QDs)。制备的ZnO量子点分别在不同温度下退火,利用透射电子显微镜(TEM)、X射线衍射(XRD)、光致发光光谱(PL)、紫外吸收光谱(UV)、场致发射曲线(JE)研究了纳米产物的结构和光电性质。获得的产物为单相纤锌矿结构ZnO,且观测到经过不同温度退火的ZnO量子点形貌发生了改变。随着退火温度增高,ZnO纳米晶体带隙降低,晶粒尺寸增大,光学性能发生改变,且改善了ZnO量子点阴极的场致发射性能,并分析了光电性能改变的主要原因。     

水热法制备氧化锌阵列及其形貌控制

低温条件下, 采用水热法, 通过控制前驱溶液的pH值, 在预先镀有ZnO纳米膜的导电玻璃衬底上制备了形貌各异的ZnO阵列, 用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)和紫外-可见分光光度计等分析手段对ZnO纳米棒的结构和形貌进行了表征. 同时还对不同形貌阵列的形成机理进行探讨. 结果表明, 所制ZnO纳米棒为单晶, 沿c轴择优生长. 在pH值为10.5左右时, 能得到取向性好、直径均匀(d~nm)的ZnO纳米棒阵列. 光学测试表明, 在可见光区透光度超过80%, 禁带宽度约为3.25eV.     

纳米氧化锌的溶剂热法合成及其光学性能

以醋酸锌为原料,以乙二胺一水为混合溶剂,利用溶剂热法低温快速制备出分散均匀的氧化锌(ZnO)纳米粒子.探讨了溶剂热条件如温度和时间对于ZnO纳米晶的形成及其形貌和光学性能的影响.X-射线粉末衍射和能量散射x-射线能谱分析表明,产物是纯的六方纤锌矿结构的ZnO.透射电镜形貌观察显示,产物为均匀纳米粒子,直径为20～30 nm.所合成粉体紫外可见光谱表明,其紫外吸收大约为2.98eV,计算其直接带隙宽度为3.10eV.光致发光光谱显示ZnO纳米粒子具有良好的结晶性和光学性质.     

基于硅纳米孔柱阵列的Zn掺杂CdS纳米晶光学特性研究

利用化学水浴法在硅纳米孔柱陈列(Si-NPA)上沉积了硫化镉(CdS)纳米晶,制得硫化镉/硅纳米孔柱阵列(CdS/Si-NPA)纳米异质结,并对非掺杂和锌(Zn)掺杂CdS/Si-NPA进行表征。研究结果表明:CdS/Si-NPA的结构保持了Si-NPA的规则阵列结构,通过加入一定量的氯化锌,实现了Zn对CdS的掺杂,Zn掺杂后的CdS晶粒大小由约18.1nm减小为约17.6nm,Zn的掺入导致了CdS/Si-NPA的光学带隙由约2.45eV增大到约2.49eV,Zn的掺杂能有效调控CdS带隙。     

ZnO/CdS复合纳米粒子的热分解合成及发光性能

设计了简单的化学反应路线,在表面活性剂PEG400存在下通过简单的前驱体热分解反应合成了ZnO/CdS复合纳米粒子,其直径在4~10nm之间。前驱体则通过室温固相反应获得。用X射线衍射仪(XRD)和透射电子显微镜(TEM))对产物的结构和形貌进行了表征。同时,对产物的光致发光性能(PL)作了测试。结果表明:ZnO/CdS复合纳米粒子在380 nm处有一个较弱的归因于近带隙发射的发光峰,550 nm处较强的发射峰来自于由氧空位形成的深浅表面态所捕获的电子-空穴对的复合。另外,对它们的形成机理进行了简单的探讨。     

低温水热法生长ZnO纳米棒阵列的电子结构及光学特性(英文)

使用低温水热法在Si衬底上生长ZnO纳米棒阵列.通过X射线衍射和扫描电子显微镜对ZnO纳米棒的结晶性和形貌进行观测.结果表明,六棱柱形ZnO纳米棒沿c轴方向的阵列性良好,且均匀致密的生长在衬底上.室温光致发光谱表明应用低温水热法可以得到光学性质良好的ZnO纳米棒阵列.使用同步辐射对ZnO纳米棒阵列的氧K带边进行X射线吸收近带边谱测量,研究了不同半径ZnO纳米棒阵列的局部电子结构及其半径对电子结构的影响.另外,对ZnO纳米棒及ZnO薄膜的局部电子结构进行了对比研究.     

高压PLD法生长ZnO和Zn1-xMgxO纳米棒及其荧光性能

利用自主设计、组装的高压脉冲激光沉积(PLD)系统,研究了温度、靶材、催化剂厚度等生长参数对ZnO和Zn1-xMgxO纳米棒生长的影响,并对ZnO纳米棒的生长机理和Zn1-xMgxO纳米棒的光致发光性能进行了探讨.实验发现,当金膜催化剂厚度为2 nm、温度为925℃时,在单晶Si衬底上生长了直径均匀的ZnO纳米棒阵列,且具有明显的(002)择优生长取向.实验发现温度与催化剂厚度是影响ZnO纳米棒的直径和生长密度的重要因素.据此提出了ZnO纳米棒阵列的高压PLD生长过程应为气–液–固和气–固相结合的生长机制.通过在ZnO靶材中掺入氧化镁,获得了Zn1-xMgxO纳米线和纳米带结构,但生长无明显的择优取向.光致发光谱测量表明,镁掺杂明显增大了ZnO的带隙,但也在其禁带中引入了缺陷能级,导致可见发光明显增强.     

高压PLD法生长p型钠掺杂氧化锌纳米线阵列

采用高压脉冲激光沉积法(HP-PLD)研究了压强、金催化层厚度对钠掺杂氧化锌纳米线(ZnO:Na)生长的影响, 并制备了ZnO:Al薄膜/ZnO:Na纳米线阵列同质pn结器件。实验发现, 当金膜厚度为4.2 nm, 生长压强为3.33×10⁴ Pa, 生长温度为875℃时, 可在单晶Si衬底上生长c轴取向性良好的ZnO纳米线阵列。X射线衍射和X射线光电子能谱综合分析证实了Na元素成功掺入ZnO纳米线晶格中。在低温(15 K)光致发光谱中, 观测到了一系列由Na掺杂ZnO产生引起的受主光谱指纹特征, 如中性受主束缚激子峰(3.356 eV, A0X)、导带电子到受主峰(3.312 eV, (e, A0))和施主受主对发光峰(3.233 eV, DAP)等。通过在ZnO:Al薄膜上生长ZnO:Na纳米线阵列形成同质结, 测得I-V曲线具有明显的整流特性, 证实了ZnO:Na纳米线具有良好的p型导电性能。     

VO2(B)/ZnO异质复合纳米棒结构的室温NH3敏感性能研究

以VO₂(B)纳米棒为内核, 利用液相生长法制备了VO₂(B)/ZnO异质复合纳米棒, 研究了ZnO生长溶液浓度对复合结构微观形貌和气敏性能的影响规律。采用扫描电子显微镜和X射线衍射仪对复合结构样品的微观形貌和结晶取向进行表征, 并测试了复合结构对NH₃的敏感性能。实验结果表明, 随着ZnO种子液浓度的增大, ZnO逐渐由纳米颗粒生长为纳米棒结构, 当ZnO种子液浓度为0.01 mol/L时, ZnO呈棒状沿径向发散生长在VO₂(B)纳米棒表面, 形成树枝状VO₂(B)/ZnO异质复合纳米棒结构, 这一结构在室温下表现出对NH₃的高灵敏度和突出的选择性, 其灵敏度最大可达5.6, 对NH₃的响应时间最短仅为2 s。在室温下表现出的优良NH₃敏感性能, 主要与高密度的VO₂(B)/ZnO异质结和树枝状结构有关。研究结果为低功耗高灵敏度NH₃气敏传感器的研制提供了重要依据。     

N-Type Field-Effect Transistors Using Multiple Mg-Doped ZnO Nanorods

Nanorod field-effect transistors (FETs) that use multiple Mg-doped ZnO nanorods and a SiO₂ gate insulator were fabricated and characterized. The use of multiple nanorods provides higher on-currents without significant degradation in threshold voltage shift and subthreshold slopes. It has been observed that the on-currents of the multiple ZnO nanorod FETs increase approximately linearly with the number of nanorods, with on-currents of ~1 muA per nanorod and little change in off-current (~4times10^-12). The subthreshold slopes and on-off ratios typically improve as the number of nanorods within the device channel is increased, reflecting good uniformity of properties from nanorod to nanorod. It is expected that Mg dopants contribute to high n-type semiconductor characteristics during ZnO nanorod growth. For comparison, nonintentionally doped ZnO nanorod FETs are fabricated, and show low conductivity to compare with Mg-doped ZnO nanorods. In addition, temperature-dependent current-voltage characteristics of single ZnO nanorod FETs indicate that the activation energy of the drain current is very low (0.05-0.16 eV) at gate voltages both above and below threshold     

Thermally and optically induced irreversible changes in some Ge–As–S amorphous thin films

Thermally and optically induced irreversible changes in the optical gap and refractive index were studied for sulphur rich, nearly stoichiometric and sulphur poor Ge–As–S amorphous films prepared by thermal evaporation. For films studied the optical gap in the virgin state decreases from 2.55₉ (Ge_0.121As_0.172S_0.707) to 1.63₂ eV (Ge_0.254As_0.294S_0.452) and simultaneously the refractive index increases from 2.21 to 2.87, respectively. The most sensitive composition to illumination seems to be nearly stoichiometric film (Ge_0.153As_0.201S_0.646), where the blue shift of the gap is observed close to 150 meV. Sulphur poor film (Ge_0.254As_0.294S_0.452) was found insensitive to illumination. Highest thermally induced blue shift of the gap, close to 250 meV, we observed just for Ge_0.254As_0.294S_0.452 film and for this film it was observed also nearly “giant” decrease in refractive index from 2.85 to 2.42. The behaviour of Ge_0.254As_0.294S_0.452 film is qualitatively discussed using the concept of network rigidity (insensitivity to illumination) and assuming thermally induced changes in bonding arrangement (refractive index changes).     

A ZnO nanorod inorganic/organic heterostructure light-emitting diode emitting at 342 nm

An inorganic/organic heterostructure light-emitting diode consisting of the hole-transporting layer N, N'-di(naphth-2-yl)- N, N'-diphenylbenzidine (NPB) and n-type ZnO nanorods fabricated by hydrothermal decomposition is reported. Poly(methyl methacrylate) was used to form a smooth surface on top of ZnO nanorod array with ZnO nanorod tops exposed for subsequent NPB deposition. An unusual ultraviolet emission at 342 nm was observed in the electroluminescence spectrum. Compared to band gap energy of ZnO (3.37 eV), the excitonic emission is blue-shifted and broadened. The mechanism of the blue shift is discussed in terms of the energy band diagram of the heterostructure.     

Synthesis and optical properties of nanocrystalline V-doped ZnO powders

This paper reports the synthesis and optical properties of nanocrystalline powders of V-doped ZnO (i.e. Zn_0.95V_0.05O, Zn_0.90V_0.10O, and Zn_0.85V_0.15O) by a simple sol–gel method using metal acetylacetonates of Zn and V and poly(vinyl alcohol) as precursors. Structure of the prepared samples was studied by X-ray diffraction, FTIR spectroscopy, and selected-area electron diffraction (SAED) analysis. The morphology of the powders revealed by SEM and TEM was affected by the amount of V, causing the formations of both nanoparticles and nanorods in the Zn_0.95V_0.05O sample, nanorods in the Zn_0.90V_0.10O sample, and nanoparticles in the Zn_0.85V_0.15O sample. The optical properties of the samples were investigated by measuring the UV–VIS absorbance and photoluminescence spectra at room temperature. All the samples exhibited UV absorption at below 400 nm (3.10 eV) with a well-defined absorbance peak at around 364 nm (3.41 eV) and 288 nm (4.31 eV). The band gap of the V-doped samples shows a decrease with increasing V concentration. The photoluminescence spectra of all the samples showed a strong UV emission band at 2.98 eV, a weak blue band at 2.82 eV, a week blue–green band at 2.56 eV, and a weak green band at 2.34 eV, which indicated their high structural and optical quality.     

Controllable synthesis of vertically aligned ZnO nanorod arrays in aqueous solution

High-density well-aligned ZnO nanorod array was successfully synthesized on a large-area magnetron sputtering deposited Al doped ZnO film-coated Si (AZO/Si) substrate via a convenient solution method. X-ray diffraction and scanning electron microscopy show that the nanorods are well-oriented perpendicular to the substrate. The influences of the reaction temperature, time, on the size and shapes of the as-prepared ZnO nanorods (ZNs) samples have been studied. The length and diameter of the nanorods became bigger when a longer reaction time was used. When the temperature is elevated to 130 degrees C, a new conical ZNs was synthesized. Room-temperature photoluminescence (PL) spectra of all the ZnO products showed a strong ultraviolet (UV) emission. The photoluminescence from free excitons of the ZNs synthesized at higher temperature reflects the high purity and nearly defect free structure of nanorods. The well-aligned feature of the nanorod array is attributed to the nanorods' epitaxial growth from the AZO films.     

Low-temperature growth and optical properties of Ce-doped ZnO nanorods

Ce-doped ZnO nanorod arrays were grown on zinc foils by a hydrothermal method at 180°C. The effects of Ce-doping on the structure and optical properties of ZnO nanorods were investigated in detail. The characterisation of the rod array with X-ray diffraction and X-ray photoelectron spectroscopy indicated that Ce³⁺ ions were incorporated into the ZnO lattices. There were no diffraction peaks of Ce or cerium oxide in the pattern. From UV-Vis spectra, we observed a red shift in the wavelength of absorption and decreased band gap due to the Ce ion incorporation in ZnO. The photoluminescence integrated intensity ratio of the UV emission to the deep-level green emission (I _UV/I _DLE) was 1.25 and 2.87, for ZnO and Ce-doped ZnO nanorods, respectively, which shows a great promise for the Ce-doped ZnO nanorods with applications in optoelectronic devices.     

Electrodeposition of template free hierarchical ZnO nanorod arrays via a chloride medium

We have successfully grown template and buffer free ZnO nanorod films via chloride medium by controlling bath temperature in a simple and cost effective electrochemical deposition method. Thin films of ZnO nano-rods were obtained by applying a potential of ?0.75 V by employing Ag/AgCl reference electrode for 4 h of deposition time. The CV measurements were carried out to determine potential required to deposit ZnO nanorod films whereas chronoamperometry studies were carried out to investigate current and time required to deposit ZnO nanorod films. The formation of ZnO nanorod has been confirmed by scanning electron microscopy (SEM) and Raman spectroscopy. Low angle XRD analysis confirms that ZnO nanorod films have preferred orientation along (101) direction with hexagonal wurtzite crystal structure. The SEM micrographs show nice surface morphology with uniform, dense and highly crystalline hexagonal ZnO nanorods formation. Bath temperature has a little influence on the orientation of nanorods but has a great impact on their aspect ratio. Increase in bath temperature show improvement in crystallinity, increase in diameter and uniform distribution of nanorods. Compositional analysis shows that the amount of oxygen is ~49.35 % and that of Zn is ~50.65 %. The optical band gap values were found to be 3.19 and 3.26 eV for ZnO nanorods prepared at bath temperature 70 and 80 °C respectively. These results indicate that by controlling the bath temperature band gap of ZnO nanorods can be tailored. The obtained results suggest that it is possible to synthesize ZnO nanorod films by a simple, cost effective electrodeposition process which can be useful for opto-electronic devices fabrication.     

多孔棒状FeVO4的制备及可见光催化性能研究

以Fe(NO₃)₃和NH₄VO₃为无机源, 氨水为pH调节剂, 采用水热法制备了多种形貌纯三斜相的多孔FeVO₄。采用X射线衍射、扫描电子显微镜和紫外-可见漫反射光谱等技术表征了样品的物理性质。结果表明, 水热温度和反应液的pH对晶相结构和粒子形貌有较大的影响: 当水热温度为180℃, 反应液的pH为4.0或7.0时, 可制得多孔三斜相FeVO₄纳米棒; 当水热温度为120℃, 反应液的pH为4.0 时制得的三斜相FeVO₄为片状结构; 而当水热温度为180℃, 反应液的pH升至10.0或水热温度变为240℃, 反应液的pH保持4.0不变时均制得含有少量FeVO₄的Fe₂O₃。在可见光照射光催化降解甲基橙的反应中, 具有最高比表面积(10.4 m²/g)的多孔棒状FeVO₄光催化活性最高, 这是因为它具有最高的结晶度、比表面积和表面氧空位密度、多孔结构和最低的带隙能。