Ultraviolet emission of ZnO film prepared by electrophoretic deposition

We deposited high quality ZnO film by electrophoretic deposition (EPD) using high quality ZnO powder prepared by solid-state pyrolytic reaction. X-ray photoelectron spectroscopy (XPS) and the infrared (IR) absorption spectrum clearly indicate that the ZnO phase powder has been prepared. Transmission electron microscope (TEM) imaging and x-ray diffraction (XRD) show that the average grain size of the powder is about 20nm. XRD and selected-area electron diffraction (SAED) reveal that the ZnO film has a polycrystalline hexagonal wurtzite structure. Only a strong ultraviolet emission peak at 390nm can be observed at room temperature.     

脉冲激光沉积法制备的ZnO薄膜的低阈值电抽运紫外随机激射

分别采用直流反应溅射法和脉冲激光沉积法在硅衬底上沉积ZnO薄膜, 用X射线衍射、扫描电镜、光致发光谱等手段对两种方法沉积的ZnO薄膜的结晶状态、 表面形貌和光致发光等进行了表征. 进一步对比研究了以上述两种方法制备的ZnO薄膜作为发光层的金属-绝缘体-半导体结构器件的电抽运紫外随机激射. 结果表明, 与以溅射法制备的ZnO薄膜作为发光层的器件相比, 以脉冲激光沉积法制备的ZnO薄膜为发光层的器件具有更低的紫外光随机激射阈值电流和更高的输出光功率. 这是由于脉冲激光沉积法制备的ZnO薄膜中的缺陷更少, 从而显著地减少了紫外光在光散射过程中的光损耗. 关键词： 随机激射 ZnO薄膜 脉冲激光沉积 溅射     

分步法高速沉积微晶硅薄膜

为提高微晶硅薄膜的纵向结晶性能, 在甚高频等离子体增强化学气相沉积技术的基础上, 采用过渡参数缓变和两步法相结合的方法在普通玻璃衬底上高速沉积薄膜. 当功率密度为2.1 W/cm², 硅烷浓度在6%和9.6%之间变化时, 从薄膜方向和玻璃方向测算的Raman晶化率的差异维持在2%以内. 硅烷浓度为9.6%时, 薄膜沉积速率可达3.43 nm/s, 从薄膜方向和玻璃方向测算的Raman晶化率分别为50%和48%, 差异的相对值仅为4.0%. 合理控制过渡阶段的参数变化, 可使两个方向的Raman晶化率差值下降到一个百分点. 表明采用新方法制备薄膜, 不仅可以抑制非晶孵化层的形成, 改善微晶硅薄膜的纵向结构, 还为制备优质薄膜提供了较宽的参数变化空间. 关键词： 微晶硅薄膜 非晶孵化层 高速沉积 甚高频等离子体增强化学气相沉积     

离子束增强沉积制备p型氧化锌薄膜及其机理研究

采用离子束增强沉积方法在Si和SiO₂/Si衬底上制备In-N共掺杂ZnO薄膜(INZO)，溅射靶是用ZnO和2 atm% In₂O₃粉体均匀混合并压制而成，在氩离子溅射ZnO靶的同时，氮、氩混合离子束垂直注入沉积的薄膜.实验结果显示INZO薄膜具有(002)的择优取向，并且为p型导电，电阻率最低为0.9Ωcm.薄膜在氮气、氧气气氛下退火，对薄膜的结构和电学特性与成膜和退火条件的关系进行了分析. 关键词： 氧化锌薄膜 p型掺杂 离子束增强沉积     

Regrowth of ZnO thin film with high surface flatness and enhanced optical properties on annealed buffer layers by rf sputtering deposition

We report a study on improving the surface flatness, optical properties, and crystallinity of ZnO thin films by rf sputtering deposition. ZnO thin films grown on sapphire substrate were first exposed to post-growth annealing, and then used to regrow high-quality ZnO thin films on top. Under the same deposition conditions, the regrown ZnO layers showed much improved crystallinity, surface flatness and enhanced optical properties. The effect of the annealed layer in improving the quality of the ZnO thin film is discussed in terms of characterization results from crystal orientation, surface morphology, and photoluminescence. It was clearly observed that, during the annealing process, the ZnO grains coalesced to form larger grains and smoother surfaces, with better crystallinity and fewer defects, which resulted in the much improved quality of the regrown ZnO thin films.     

Double‐layer channel structure based ZnO thin‐film transistor grown by atomic layer deposition

A double channel structure has been used by depositing a thin amorphous‐AlZnO (a‐AZO) layer grown by atomic layer deposition between a ZnO channel and a gate dielectric to enhance the electrical stability. The effect of the a‐AZO layer on the electrical stability of a‐AZO/ZnO thin‐film transistors (TFTs) has been investigated under positive gate bias and temperature stress test. The use of the a‐AZO layer with 5 nm thickness resulted in enhanced subthreshold swing and decreased V_th shift under positive gate bias/temperature stress. In addition, the falling rate of the oxide TFT using a‐AZO/ ZnO double channel had a larger value (0.35 eV/V) than that of pure ZnO TFT (0.24 eV/V). These results suggest that the interface trap density between dielectric and channel was reduced by inserting a‐AZO layer at the interface between the channel and the gate insulator, compared with pure ZnO channel. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical and electrical properties of aluminum-doped ZnO thin films grown by pulsed laser deposition

Transparent aluminum-doped zinc oxide (AZO) thin films were deposited on quartz glass substrates by pulsed laser deposition (PLD) from ablating Zn-Al metallic targets. The structural, electrical and optical properties of these films were characterized as a function of Al concentration (0-8 wt.%) in the target. Films were deposited at a low substrate temperature of 150 °C under 11 Pa of oxygen pressure. It was observed that 2 wt.% of Al in the target (or 1.37 wt.% of Al doped in the AZO film) is the optimum concentration to achieve the minimum film resistivity and strong ultraviolet emission. The presence of Al in the ZnO film changes the carrier concentration and the intrinsic defects.     

磁控溅射ZnO薄膜的成核机制及表面形貌演化动力学研究

利用原子力显微镜分析了ZnO薄膜在具有本征氧化层的Si(100)和Si(111)基片上的表面形貌 随沉积时间的演化. 通过对薄膜生长形貌的动力学标度表征，研究了射频反应磁控溅射条件 下，ZnO薄膜的成核过程及生长动力学行为. 研究发现，ZnO在基片表面的成核过程可分为初 期成核阶段、低速率成核阶段和二次成核阶段. 对于Si(100)基片，三个成核阶段的生长指 数分别为β₁=1.04，β₂=0.25±0.01，β₃=0.74；对 于Si(11 关键词： ZnO薄膜 磁控溅射 生长动力学 成核机制     

Fabrication of p-type Li-doped ZnO films by pulsed laser deposition

p-Type ZnO thin films have been realized via doping Li as acceptor by using pulsed laser deposition. In our experiment, Li₂CO₃ was used as Li precursor, and the growth temperature was varied from 400 to 600 °C in pure O₂ ambient. The Li-doped ZnO film prepared at 450 °C possessed the lowest resistivity of 34 Ω cm with a Hall mobility of 0.134 cm² V⁻¹ s⁻¹ and hole concentration of 1.37 × 10¹⁸ cm⁻³. X-ray diffraction (XRD) measurements showed that the Li-doped ZnO films grown at different substrate temperatures were of completely (0 0 2)-preferred orientation.     

Effects of annealing treatment on the formation of CO2 in ZnO thin films grown by metal-organic chemical vapor deposition

Post-growth annealing was carried out on ZnO thin films grown by metal-organic chemical vapor deposition (MOCVD). The grain size of ZnO thin film increases monotonically with annealing temperature. The ZnO thin films were preferential to c-axis oriented after annealing as confirmed by X-ray diffraction (XRD) measurements. Fourier transformation infrared transmission measurements showed that ZnO films grown at low temperature contains CO₂ molecules after post-growth annealing. A two-step reaction process has been proposed to explain the formation mechanism of CO₂, which indicates the possible chemical reaction processes during the metal-organic chemical vapor deposition of ZnO films.     

The super hydrophobicity of ZnO nanorods fabricated by electrochemical deposition method

Electrochemical deposition method was employed to fabricate ZnO nanorods on zinc foil substrate in this paper. The structural observations of ZnO nanorods with different aspect ratios were carried out by field-emission scanning electron microscopy. The microstructures of ZnO nanorods were also characterized by X-ray diffraction and the changes in surface hydroxyls with electrochemical deposition time were analyzed by X-ray photoelectron spectroscopy. The study results show the aspect ratios of ZnO nanorods and the density of their surface hydroxyls are responsible for their superhydrophobicity. The fluorinated polymer coated ZnO nanorods showed an excellent superhydrophobic behavior with 167° contact angle of water droplet, which is larger than that of fluorinated polymer flat surface. The more the surface hydroxyls are, the more hydrophilic the surfaces are. Meanwhile, the larger the aspect ratio of ZnO nanorod arrays is, the larger its drophobicity is. The results of this study might pave a simple and feasibility pathway to the fabrication of superhydrophobic cleaning materials used in engineering fields.     

原子层沉积法 生长ZnO的性质与前驱体源量的关系研究

介绍了新型材料ZnO的各项性能,并采用原子层沉积方法制备新型材料ZnO. 实验中采用二乙基锌(DEZn) 和水作为生长ZnO的前驱体源, 在蓝宝石衬底上生长ZnO; 采用氮气作为载气, 生长温度为180℃. 通过改变在实验中的通入锌源的时间, 探索不同的DEZn的源的量对薄膜的成分(Zn/O)、薄膜的厚度、生长速率、晶型、 表面形貌、三维形貌以及粗糙度的影响. 关键词： 氧化锌 原子层沉积 Zn/O     

Electrical characterisation of phosphorus-doped ZnO thin films grown by pulsed laser deposition

Phosphorus-doped ZnO films were grown by pulsed laser deposition using a ZnO:P₂O₅-doped target as the phosphorus source with the aim of producing p-type ZnO material. ZnO:P layers (with phosphorus concentrations of between 0.01 to 1 wt%) were grown on a pure ZnO buffer layer. The electrical properties of the films were characterised from temperature dependent Hall-effect measurements. The samples typically showed weak n-type conduction in the dark, with a resistivity of 70 Ω cm, a Hall mobility of μ_n0.5 cm² V ⁻¹ s⁻¹ and a carrier concentration of n3×10¹⁷ cm⁻³ at room temperature. After exposure to an incandescent light source, the samples underwent a change in conduction from n- to p-type, with an increase in mobility and decrease in concentration for temperatures below 300 K.     

ZnO薄膜的激子能量和束缚能的计算

采用有效质量近似，将耦合在一起的6×6价带本征方程分开来考虑, 取激子试探波函数为z方向和x-y平面分离的形式，用变分法计算了ZnO薄膜重空穴带激子基态能、第一激发态能、束缚能和激子的半径随薄膜厚度的变化关系，并讨论了电子波函数的量子隧穿效应对厚度d<2.0 nm薄膜的能量修正. 关键词： 激子 ZnO薄膜 纤锌矿     

Room-temperature deposition of crystalline patterned ZnO films by confined dewetting lithography

In this work patterned ZnO films were prepared at room-temperature by deposition of ∼5 nm size ZnO nanoparticles using confined dewetting lithography, a process which induces their assembly, by drying a drop of ZnO colloidal dispersion between a floating template and the substrate. Crystalline ZnO nanoparticles exhibit a strong visible (525 nm) light emission upon UV excitation (λ = 350 nm). The resulting films were characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM). The method described herein presents a simple and low cost method to prepare crystalline ZnO films with geometric patterns without additional annealing. Such transparent conducting films are attractive for applications like light emitting diodes (LEDs). As the process is carried out at room temperature, the patterned crystalline ZnO films can even be deposited on flexible substrates.     

Electrical and optical properties of Al-doped ZnO thin films by sol-gel process

Al-doped ZnO (AZO) thin films oriented along the (0 0 2) plane have been prepared by the sol-gel process and their electrical and optical properties with post-deposition heating temperature were investigated. The preferred c-axis orientation along the (0 0 2) plane was enhanced with increasing post-deposition heating temperature and the surface of the films showed a uniform and nano-sized microstructure. The electrical resistivity of the films decreased from 73 to 22 Ω cm as the post-deposition heating temperature increased from 500 to 650 °C; however, the film postheated at 700 °C increased greatly to 580 Ω cm. The optical transmittance of the films postheated below 650 °C was over 86%, but it decreased at 700 °C. The electrical and optical properties of the AZO films with post-deposition heating temperature are discussed.     

Fast synthesis of ZnO nanostructures by laser-induced chemical liquid deposition

ZnO nanostructures were obtained by directly irradiating a small volume of a solution of precursor on a fused-quartz substrate using an unfocused continuous wave CO₂ laser for 2-30 s at laser powers ranging from 20 to 40 W. The laser-based thermochemistry approach allows rapid non-isothermal heating and convection enhanced mass transport which opens new growth mechanisms for the rapid deposition of nanomaterials at predetermined locations on a substrate. The deposits consist of a variety of ZnO nanostructure morphologies, including aggregated nanoparticles, nanorods, faceted nanocrystals and nanowires. The samples were characterized by scanning and transmission electron microscopy, X-ray diffraction and photoluminescence spectroscopy. They were found to exhibit an intense room-temperature photoluminescence, which is characterized by the presence of a strong UV peak around 390 nm and no visible emission. The relationship between the PL signal characteristics and specific ZnO nanostructures was investigated in order to point up optimal nanostructures for possible luminescent devices.     

Characterization of a-plane orientation ZnO film grown on GaN/Sapphire template by pulsed laser deposition

In this study, the authors have investigated the structural and optical properties of ZnO layer grown by pulsed laser deposition on GaN/r-plane sapphire. X-ray diffraction results demonstrate the ZnO film to be highly preferentially deposited at a-axis orientation; the different rocking curve values along the two orthogonal directions indicate the low C_2v symmetry in the growth a-plane ZnO. From free stress to large tensile stress (about 1.34 × 10⁹ Pa) distribution along the growth direction of ZnO is revealed by visible Raman mapping spectra. The enhanced significantly high-order longitudinal-optical (LO) phonon modes up to 4th and no TO phonons have been observed in Raman spectrum under UV 325 nm by resonance conditions; an intense and broad disorder activated surface phonon mode is also observed, resulting from the increased disorder on the film surface with stripe-like growth features. Low-temperature photoluminescence measurements reveal that the band-edge emission of ZnO is dominated by neutral donor-bound exciton and free electrons to neutral acceptor emissions. Interfacial microstructure of ZnO/GaN has been examined by transmission electron microscopy, with the epitaxial relationship () ZnO//() GaN. All these results indicated that GaN template played an important role in the growth of ZnO film, with full advantage of small lattice mismatch.     

利用多层膜生长技术制备纳米印章模板

在纳米印章技术中，为克服电子束刻蚀制备50nm以下线条的技术难点，利用等离子增强化学 气相沉积技术制备了a-Si/SiN_x多层膜，再利用选择性湿法腐蚀或干法腐蚀在横 截面上制备出浮雕型一维纳米级模板. 多层膜子层之间界面清晰陡峭，可以在纳米量级对子 层厚度进行控制，得到了侧壁在纳米尺度上平滑的模板. 通过控制多层膜子层的生长时间， 制备出线条宽度和槽状宽度均为20nm的等间距模板，品质优于电子束刻蚀技术制备的模板. 关键词： 纳米印章模板 多层膜生长技术     

Self-catalyst synthesis of aligned ZnO nanorods by pulsed laser deposition

High-density well-aligned ZnO nanorods were successfully synthesized on ZnO-buffer-layer coated indium phosphide (InP) (100) substrates by a pulsed laser deposition (PLD) method. Scanning electron microscopy images show that the ZnO buffer layer formed uniform drip-like structure and ZnO nanorods were well-oriented perpendicular to the substrate surface. The sharp diffraction peak observed at 34.46° in X-ray diffraction scanning pattern suggests that the ZnO nanorods exhibit a (002)-preferred orientation. The PL spectra of ZnO samples shows a strong near band edge emission centered at about 380 nm and a weak deep level emission centered at around 495 nm, and it demonstrates that the ZnO nanorods produced in this work have high optical quality, which sheds light on further applications for nanodevices. Supported by the National Natural Science Foundation of China (Grant No. 50532080), the Science & Technology Foundation for Key Laboratory of Liaoning Province (Grant No. 20060131), and the Doctoral Project by China Ministry of Education (Grant No. 20070141038)