水热合成法制备ZnO纳米棒有序阵列薄膜

采用水热合成法在预先生长的ZnO种子层的玻璃衬底上制备出ZnO纳米棒有序阵列薄膜。通过X射线衍射、扫描电镜、透射电镜和选区电子衍射分析表明：所制备的薄膜由垂直于ZnO种子层的纳米棒组成,呈单晶六角纤锌矿ZnO结构,且沿[001]方向择优生长,纳米棒的平均直径和长度分别为10．0nm和3．3μm。     

TiO_2/ZnO双层电子传输层的制备及光电化学性能

首先在氟掺杂的氧化锡导电玻璃(FTO)上水热生长一层TiO_2纳米棒阵列薄膜,然后通过旋涂法旋涂ZnO籽晶层后水热法生长ZnO纳米棒得到TiO_2/ZnO纳米棒阵列薄膜。通过XRD、SEM、PL、UV-Vis和电化学工作站等对单层TiO_2纳米棒和TiO_2/ZnO纳米棒的结构、表面形貌、荧光性能、光吸收强度以及光电化学性质进行表征。结果表明,随着水热生长ZnO时间的增长,ZnO纳米棒密度增加; ZnO纳米棒的生长时间不同使其荧光强度不同,TiO_2/Zn O纳米棒的荧光强度与单层TiO_2纳米棒相比有着微小的减弱,没有明显的衍射峰; TiO_2/ZnO纳米棒复合材料比单层TiO_2的光吸收强度高,提高其光学性能,但是吸光区域都在紫外光区域;在标准模拟太阳光照射下,TiO_2/Zn O纳米棒的光电流为0. 002 m A,单层TiO_2纳米棒的光电流为0. 006 m A,复合薄膜的电流有着明显的变化。     

高定向ZnO纳米棒阵列膜的制备及其光学性能

采用阴极恒电位沉积方法,在Zn(NO3)2溶液中,用六亚甲基四胺作为形貌控制试剂,直接在氧化铟锡玻璃衬底上制备出透明致密的ZnO纳米棒阵列膜。通过X射线衍射、扫描电镜和能量色散谱表征了薄膜的形貌和结构,测量了ZnO纳米棒阵列膜的光学透射谱和光致发光谱。结果表明:所制备的具有c轴高度择优取向的ZnO纳米棒为高纯单晶纤锌矿结构,粒径约为200nm,膜的结晶度和表面平整度明显提高。ZnO薄膜在可见光区具有高透射率(80%)和陡峭的吸收边缘,室温光致发光谱显示,在380nm处存在一个尖锐的强紫外发射峰和在510nm处存在一宽带弱绿光发射峰。     

ZnO纳米棒的制备及光学性能研究

采用水热合成法在覆盖有ZnO晶种层的硅片上制备了形貌可控的ZnO纳米棒,并利用XRD、扫描电镜、拉曼光谱和光致发光光谱等测试手段对其结构及光学特性进行了研究。结果表明,所制备的ZnO纳米棒具有较强的紫外发光和较弱的深能级发光,说明所制备的ZnO纳米棒结晶质量和光学性能均较好。     

FTO薄膜表面激光诱导制备ZnO纳米结构

采用磁控溅射法在FTO(掺氟二氧化锡)玻璃基底表面沉积金属Zn层,再将其置于双氧水溶液中,通过纳秒脉冲激光对其表面进行辐照处理来实现ZnO纳米结构的制备。研究了激光能量密度和扫描速率对ZnO纳米结构的形成和得到的ZnO纳米结构复合FTO(Zn O/FTO)薄膜表面形貌和光电性能的影响。结果表明,当Zn层厚度为200 nm时,可保证FTO薄膜表面既出现完整的Zn O纳米结构,又仅有少量Zn剩余。当激光能量密度为0.80 J/cm2,扫描速率为15 mm/s时,FTO薄膜表面制备出了均匀一致性最好的ZnO纳米结构,此时ZnO/FTO薄膜有最佳的光电性能,其在400～800 nm波段的平均透光率为70.18%,平均反射率为7.10%,方块电阻为9.23Ω。     

ZnO纳米墙薄膜的低温水热制备及其性能研究

利用控制水解浸涂法在氧化铟锡(ITO)导电玻璃上制备籽晶层,进而通过低温水热法和热处理获得了独特的氧化锌(ZnO)纳米墙薄膜结构。通过X射线衍射谱(XRD)、扫描电镜(SEM)、光电子能谱(EDS)、红外光谱(FTIR)、紫外-可见光谱(UV-Vis)和光致发光谱(PL)等对薄膜的形貌、组成和结构进行了分析表征。研究表明,ZnO纳米墙由20～100 nm厚的片层交织而成,在热处理前薄膜的组成为混合的ZnO、醋酸锌(ZnAc)和羟基醋酸锌(Zn-LHS),经500°C热处理脱除CO2、H2O等小分子后基本完全转变为ZnO,而原有层状交织纳米墙结构保留下来。室温PL谱显示薄膜在383 nm处有较强烈的紫外激发峰。结合晶体生长理论探讨了ZnO纳米墙薄膜的生长机制。     

简捷微波合成氧化锌纳米棒

以氯化锌和乙二胺的水溶液为前驱体溶液,采用家用微波炉微波辐照8min,成功制备出结晶性好的半导体ZnO纳米棒.用X-射线衍射(XRD)、选区成份分析(EDS)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)和选区电子衍射花样(SAED)对产物进行了表征.结果表明,纳米棒沿着c轴择优取向生长,直径在50nm左右,长度在400～600 nm之间,粒径分布均匀.并对ZnO纳米棒的生长过程进行了简单分析.     

ZnO纳米线阵列膜的自组装生长及其金属接触特性

以磁控溅射制备的ZnO纳米晶薄膜作为籽晶层,用水热法在80℃氧化铟锡(indium tin oxide,ITO)玻璃衬底上,实现了大面积ZnO纳米线阵列膜的取向生长,制备了3种金属-半导体-金属(metal-semiconductor-metal,MSM)结构的ZnO半导体纳米线阵列膜样品,测试了薄膜样品的光学特性和I-V特性。结果表明:在相同的生长液浓度下,籽晶层对所生长的纳米线尺度分布有显著影响。所制备的纳米线薄膜在室温下具有显著的紫外带边发射特性。ZnO纳米线/Ag和ZnO纳米线/Al的金属-半导体接触均具有明显的Schottky接触特性,而ZnO纳米线/Au的金属-半导体接触具有明显Ohmic接触特性。     

ZnO/ZnS异质结构纳米棒的制备及性能研究

本文利用低温二步水热法在ITO玻璃衬底上制备了ZnO/ZnS异质结构纳米棒,研究和比较了Zn O纳米棒和ZnO/ZnS异质结构纳米棒的形貌,结构和光学等特性。结果表明:未掺杂的ZnO纳米棒具有明显的六角结构表面,良好的晶体结构和c轴生长取向;ZnO/ZnS异质结构纳米棒的形貌和光学性质都发生了变化,纳米棒直径变化范围大,六角结构表面六边形不规则,且引入了较多的深能级缺陷。     

沉积次数对CdS/TiO_2复合纳米薄膜光电性能的影响

采用水热法在FTO导电玻璃基底表面制备了结构规整的TiO2纳米棒阵列,利用连续离子层吸附反应(SILAR)法在TiO2纳米棒阵列表面沉积生长了CdS量子点,采用紫外可见分光光度计和电化学工作站表征了薄膜的光学和光电性能,随着CdS循环次数的增加,薄膜的光电响应越明显,当CdS循环沉积次数为9次时,薄膜的光电响应程长约为514μA/cm2。     

Controllable size and photoluminescence of ZnO nanorod arrays on Si substrate prepared by microwave-assisted hydrothermal method

High-quality ZnO nanorod arrays were grown on silicon substrates by microwave-assisted hydrothermal method. A ZnO seed layer deposited by magnetron sputtering was used for promoting nanorod growth. Process optimization indicates that the size and surface density of nanorods can be controlled individually by varying process parameters including precursor concentration, heating temperature, and heating time. The photoluminescence performance of the nanorods is closely dependent on the mean size of the rods. Reducing rod diameter leads to decreased UV emission and visible emission intensity ratio, which has been attributed to the increased impurities or defects on the rod surface. The present results provide a feasible approach to modify the optical properties of transparent ZnO nanorod arrays.     

Seedless Pattern Growth of Quasi-Aligned ZnO Nanorod Arrays on Cover Glass Substrates in Solution

A hybrid technique for the selective growth of ZnO nanorod arrays on wanted areas of thin cover glass substrates was developed without the use of seed layer of ZnO. This method utilizes electron-beam lithography for pattern transfer on seedless substrate, followed by solution method for the bottom-up growth of ZnO nanorod arrays on the patterned substrates. The arrays of highly crystalline ZnO nanorods having diameter of 60 ± 10 nm and length of 750 ± 50 nm were selectively grown on different shape patterns and exhibited a remarkable uniformity in terms of diameter, length, and density. The room temperature cathodluminescence measurements showed a strong ultraviolet emission at 381 nm and broad visible emission at 585–610 nm were observed in the spectrum.     

Structural and optical properties of ZnO nanorods by electrochemical growth using multi-walled carbon nanotube-composed seed layers

We reported the enhancement of the structural and optical properties of electrochemically synthesized zinc oxide [ZnO] nanorod arrays [NRAs] using the multi-walled carbon nanotube [MWCNT]-composed seed layers, which were formed by spin-coating the aqueous seed solution containing MWCNTs on the indium tin oxide-coated glass substrate. The MWCNT-composed seed layer served as the efficient nucleation surface as well as the film with better electrical conductivity, thus leading to a more uniform high-density ZnO NRAs with an improved crystal quality during the electrochemical deposition process. For ZnO NRAs grown on the seed layer containing MWCNTs (2 wt.%), the photoluminescence peak intensity of the near-band-edge emission at a wavelength of approximately 375 nm was enhanced by 2.8 times compared with that of the ZnO nanorods grown without the seed layer due to the high crystallinity of ZnO NRAs and the surface plasmon-meditated emission enhancement by MWCNTs. The effect of the MWCNT-composed seed layer on the surface wettability was also investigated.     

Selective Growth of Vertical-aligned ZnO Nanorod Arrays on Si Substrate by Catalyst-free Thermal Evaporation

By thermal evaporation of pure ZnO powders, high-density vertical-aligned ZnO nanorod arrays with diameter ranged in 80–250 nm were successfully synthesized on Si substrates covered with ZnO seed layers. It was revealed that the morphology, orientation, crystal, and optical quality of the ZnO nanorod arrays highly depend on the crystal quality of ZnO seed layers, which was confirmed by the characterizations of field-emission scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and photoluminescence measurements. For ZnO seed layer with wurtzite structure, the ZnO nanorods grew exactly normal to the substrate with perfect wurtzite structure, strong near-band-edge emission, and neglectable deep-level emission. The nanorods synthesized on the polycrystalline ZnO seed layer presented random orientation, wide diameter, and weak deep-level emission. This article provides a C-free and Au-free method for large-scale synthesis of vertical-aligned ZnO nanorod arrays by controlling the crystal quality of the seed layer.     

Growth temperature dependent properties of ZnO nanorod arrays on glass substrate prepared by wet chemical method

In this work, ZnO nanorod arrays were grown on glass substrate by the wet chemical method, and the effect of synthesis temperature on the properties was investigated. The grown nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman and Photoluminescence (PL) measurements. XRD pattern showed that nanorod prepared at 80 °C and 90 °C has high crystallinity with wurtzite structure and orientated along the c-axis. However, nanorods were not formed at 60 °C and 70 °C due to less energy supply for the growth of the ZnO. FE-SEM results showed that the morphology and the size of ZnO can be effectively controlled. In particular, as the temperature increased, diameter of the nanorod was increased while length decreased. Raman scattering spectra of ZnO nanorod arrays revealed the characteristic E₂^high mode that is related to the vibration of oxygen atoms in the wurtzite ZnO. Room-temperature PL spectra of the ZnO nanorods revealed a near-band-edge (NBE) emission peak. The NBE (UV light emission) band at ~383 nm might be attributed to the recombination of free exciton. The narrow full-width at half-maximum (FWHM) of the UV emission indicated that ZnO nanorods had high crystallinity.     

Growth of vertically aligned ZnO nanorods using textured ZnO films

A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells.

PACS

61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)     

Effect of ZnO seed layers on the solution chemical growth of ZnO nanorod arrays

High density ZnO nanorod arrays were grown on Si substrates coated with ZnO seed layers via aqueous solution route. The ZnO seed layers were deposited on the substrate using DC reactive sputtering and RF magnetron sputtering. It was found that ZnO seed layer with (1 0 3) preferred orientation, prepared using DC reactive sputtering, did not facilitate the formation of ZnO nanorods in the solution grown process. Prior seeding of the surface by ZnO layer with (0 0 2) preferred orientation, deposited using RF magnetron sputtering, leads to nucleation sites on which ZnO nanorod arrays can grow in a highly aligned fashion. ZnO nanorods with well-defined hexagonal facets (0 0 2) were grown almost vertically over the entire substrate. The uniformity and alignment of the nanorod arrays are strongly related to the properties of underneath ZnO seed layers.     

Fabrication and characterization of silicon wire solar cells having ZnO nanorod antireflection coating on Al-doped ZnO seed layer

In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it.     

Effects of coffee ring via inkjet printing seed layers on field emission properties of patterned ZnO nanorods

Inkjet printing, a fast, simple, efficient graphical deposition technology, is first applied to achieve high-quality emission arrays. Patterned arrays of ZnO nanorods have been successfully synthesized via hydrothermal method after inkjet printing the ZnO seed layer. During printing, different substrate temperatures were found to affect the morphology, microstructure and field emission (FE) properties of ZnO arrays. The results showed that the FE performance was improved when the coffee ring effect was eliminated by raising the substrate temperature due to higher aspect ratio of the nanorods. Both the compensating flow characteristics inside the droplets and the mechanism of regulating the rheological behavior of the solution during inkjet printing were analyzed to inhibit the effect of coffee ring, which played an important role in the later patterning electrode construction of emission arrays. The selective growth of the emitter material can be easily realized by introducing the direct patterning technology of inkjet printing in the preparation of field emission electron source.