自供能ZnO/ZnS异质结紫外探测器的性能研究

用化学浴法在ZnO纳米棒表面沉积ZnS制备出ZnO/ZnS核壳纳米棒阵列,使用SEM、XRD和XPS等手段表征了样品的形貌、结构和成分。结果表明,ZnO/ZnS核壳纳米棒阵列表面粗糙,生长致密、分布均匀,其平均直径约为150 nm。以Pt为对电极组装的自供能ZnO/ZnS异质结紫外探测器,对紫外光具有很好的探测性能,能循环工作且性能稳定。这种探测器对微弱的紫外光也有较强的响应和较高的光敏性,且随着光强度的提高光电流密度线性增大。与自供能ZnO纳米棒紫外探测器相比,ZnO/ZnS异质结紫外探测器具有更高的响应速度,上升时间和下降时间分别提高到0.02 s和0.03 s。     

Novel Structure for High Performance UV Photodetector Based on BiOCl/ZnO Hybrid Film

A novel type of high performance ultraviolet (UV) photodetector (PD) based on a ZnO film has been prepared by incorporating a BiOCl nanostructure into the film. The responsivity of the BiOCl/ZnO hybrid film PD in UV region can reach 182.87 mA W^?1, which is about 2.72 and 6.87 times for that of TiO₂/ZnO hybrid film PD and pure ZnO film PD. The rise/decay time of BiOCl/ZnO hybrid film PD is 25.83/11.25 s, which is much shorter than that of TiO₂/ZnO hybrid film PD (51.94/26.05 s) and pure ZnO film PD (69.34/>120 s). The BiOCl nanostructure can inject photogenerated electrons into the ZnO film under UV light illumination, leading to the increase of photocurrent, and forms barriers to block the straight transmission of electrons between electrodes, resulting in the decrease of decay time. The results of control experiment show that the transfer path of photogenerated electrons formed by p–n junction will be cut off after depositing gold nanoparticles on the film surface, which means this hybrid film is a unique and novel structure to improve the optoelectronic performance of photodetectors. This novel BiOCl/ZnO hybrid structure paves new route for the development of film PDs based on ZnO film.     

Novel Transparent and Self‐Powered UV Photodetector Based on Crossed ZnO Nanofiber Array Homojunction

A novel self‐powered UV photodetector based on electrospun ZnO nanofiber arrays is introduced. Aligned pure ZnO nanofibers and Ag‐doped p‐type ZnO nanofibers are processed perpendicular to each other, and p–n junction arrays of ZnO nanofibers are fabricated as a result. Owing to the intrinsic intervals between nanofibers, the device is fully transparent on quartz substrate. Various characterization methods including TEM, XRD, and XPS are used to testify the existence form of Ag element in ZnO nanofibers, and a field effect transistor is constructed to judge their conductivity. It is discovered that the Ag doping process not only transforms ZnO to p‐type conductivity, making it possible to build this self‐powered photodetector, but also forms Ag nanoparticles in ZnO nanofibers and thus helps reduce the response time. Benefiting from the abovementioned dual effects, this UV detector is found to have an enhanced performance, with the on–off ratio up to 10⁴ at zero bias and a rather short rise/decay time of 3.90 s/4.71 s.     

Ultrahigh Responsivity UV Photodetector Based on Cu Nanostructure/ZnO QD Hybrid Architectures

Strong near‐surface electromagnetic field formed by collective oscillation of electrons on Cu nanostructure a shows a strong dependence on geometry, offering a promising approach to boost the light absorption of ZnO photoactive layers with enhanced plasmon scattering. Here, a facile way to fabricate UV photodetectors with tunable configuration of the self‐assembled Cu nanostructures on ZnO thin films is reported. The incident lights are effectively confined in ZnO photoactive layers with the existence of the uplayer Cu nanostructures, and the interdiffusion of Cu atoms during fabrication of the Cu nanostructures can improve the carrier transfer in ZnO thin films. The optical properties of the hybrid architectures are successfully tailored over a control of the geometric evolution of the Cu nanostructures, resulting in significantly enhanced photocurrent and responsivity of 2.26 mA and 234 A W^?1 under a UV light illumination of 0.62 mW cm^?2 at 10 V, respectively. The photodetectors also exhibit excellent reproducibility, stability, and UV–visible rejection ratio (R_{370 nm}/R_{500 nm}) of ≈370, offering an approach of high‐performance UV photodetectors for practical applications.     

Ultrahigh Responsivity in Graphene–ZnO Nanorod Hybrid UV Photodetector

Ultraviolet (UV) photodetectors based on ZnO nanostructure/graphene (Gr) hybrid‐channel field‐effect transistors (FETs) are investigated under illumination at various incident photon intensities and wavelengths. The time‐dependent behaviors of hybrid‐channel FETs reveal a high sensitivity and selectivity toward the near‐UV region at the wavelength of 365 nm. The devices can operate at low voltage and show excellent selectivity, high responsivity (R_I ), and high photoconductive gain (G). The change in the transfer characteristics of hybrid‐channel FETs under UV light illumination allows to detect both photovoltage and photocurrent. The shift of the Dirac point (V _Dirac) observed during UV exposure leads to a clearer explanation of the response mechanism and carrier transport properties of Gr, and this phenomenon permits the calculation of electron concentration per UV power density transferred from ZnO nanorods and ZnO nanoparticles to Gr, which is 9 × 10¹⁰ and 4 × 10¹⁰ per mW, respectively. The maximum values of R_I and G infer from the fitted curves of R_I and G versus UV intensity are 3 × 10⁵ A W^?1 and 10⁶, respectively. Therefore, the hybrid‐channel FETs studied herein can be used as UV sensing devices with high performance and low power consumption, opening up new opportunities for future optoelectronic devices.     

Room temperature paramagnetism of ZnO:Mn films grown by RF-sputtering

ZnO:Mn transparent thin films (thickness < 1 μm) with the Mn contents ranging from 1.8 to 3.25 at.% were grown by RF magnetron co-sputtering. The films are nanocrystalline, with wurtzite-structure grains of a typical size of 20 nm and with a preferential orientation of the c-axis perpendicular to the surface. According to the Raman spectroscopy data, Mn mostly substitutes Zn in the lattice sites. In spite of these factors, the nanostructure and the Mn(Zn) substitution, that are considered favorable for ferromagnetism in this material, both magnetic resonance and Faraday effect measurements show paramagnetic behavior of the ZnO:Mn films and the absence of ferromagnetic order at room temperature.     

ZnO Film UV Photodetector with Enhanced Performance: Heterojunction with CdMoO4 Microplates and the Hot Electron Injection Effect of Au Nanoparticles

A novel CdMoO₄–ZnO composite film is prepared by spin‐coating CdMoO₄ microplates on ZnO film and is constructed as a heterojunction photodetector (PD). With an optimized loading amount of CdMoO₄ microplates, this composite film PD achieves a ≈18‐fold higher responsivity than pure ZnO film PD at 5 V bias under 350 nm (0.15 mW cm⁻²) UV light illumination, and its decay time shortens to half of the original value. Furthermore, Au nanoparticles are then deposited to modify the CdMoO₄–ZnO composite film, and the as‐constructed photodetector with an optimized deposition time of Au nanoparticles yields an approximately two‐fold higher photocurrent under the same condition, and the decay time reduces by half. The introduced CdMoO₄ microplates form type‐II heterojunctions with ZnO film and improve the photoelectric performance. The hot electrons from Au nanoparticles are injected into the CdMoO₄–ZnO composite film, leading to the increased photocurrent. When the light is off, the Schottky barriers formed between Au nanoparticles and CdMoO₄–ZnO composite film block the carrier transportation and accelerate the decay process of current. The study on Au‐nanoparticle‐modified CdMoO₄–ZnO composite film provides a facile method to construct ZnO film based PD with novel structure and high photoelectric performance.     

基于p-Se/Al2O3/n-ZnO纳米棒阵列异质结的自驱动紫外-可见光探测器

自驱动光探测器能够在无外加偏压的情况下将光信号转化为电信号, 在工业和军事领域有着广泛的应用。本研究报道了p型Se薄膜和n型ZnO纳米棒阵列异质结的可控合成以及它们作为自驱动紫外-可见光探测器的应用。由于在ZnO和Se的界面处形成的内建电场将光生电子-空穴对分离, 促使它们向相反方向传输, 最终被电极收集, 在0偏压下获得了较高的光电流(435 pA), 从而实现无线的自驱动光电探测。并且, 在Se和ZnO界面处沉积的Al₂O₃层有效降低了暗电流。最终, 此器件在500 nm的单色光下显示了高响应率55 μA·W ^-1和大比探测率5×10 ¹⁰Jones, 并表现出了极快的响应速度(上升时间0.9 ms, 衰减时间0.3 ms)。     

反应沉积法制备c轴取向ZnO薄膜及表征

以二水合醋酸Zn为原料 ,采用反应沉积方法在非晶玻璃衬底上制备出了高度c轴取向、结晶良好的ZnO薄膜。研究了不同衬底温度和Zn源温度对ZnO薄膜性质的影响 ,探讨了不同衬底温度和Zn源温度下生长ZnO薄膜的最佳参数。本文还讨论了该方法制备ZnO薄膜的沉积机制及优化条件下样品的透光特性。     

Fabrication of pure ZnO nanoparticles by polymerization method

ZnO nanoparticles have received enormous attention due to their wide range of application such as diodes, ultraviolet-protection films, catalysts, sensors, ceramics and solar energy transformation parts. In the current research, ZnO nanoparticles were prepared by polymer decomposition. Synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transition electron microscopy (TEM) and size distribution of these particles was investigated. Narrow size distribution of particles with a diameter of 20–30 nm and the regular distribution of ZnO nanoparticles were attributed to the application of poly amidoxime polymer. The results show that the polymer thermal decomposition technique is a feasible method for production of ZnO nanoparticles.     

Sn掺杂ZnO半导体纳米线的制备、表征及光学性能

采用化学气相沉积法获得了Sn掺杂含量约为2.4%(原子分数)的Sn掺杂ZnO半导体纳米线。X射线衍射结果表明,Sn的掺杂并没有改变ZnO的纤锌矿结构。掺杂纳米线的室温光致发光光谱在409.2nm和498.0nm处出现了蓝绿光发光峰。探讨了其发光机制,认为前者可能来源于从导带到Zn空位形成的浅受主能级的跃迁以及从氧空位形成的浅施主能级到价带的跃迁;而后者来源于从氧空位形成的浅施主能级到锌空位浅受主能级的跃迁。     

化学共沉淀粉体制备ZnO压敏电阻

本文采用化学共沉淀法制备了颗粒细、活性好的ZnO压敏电阻粉体,表征了粉体的性能．利用共沉淀粉体制备了α＝50、压敏电压高、通流能力大的压敏电阻．与传统氧化物机械混合粉体制得的压敏电阻比较,共沉淀粉体获得的压敏电阻微观结构均匀．     

A high-sensitivity,fast-response,rapid-recovery UV photodetector fabricated based on catalyst-free growth of ZnO nanowire networks on glass substrate

Here, we report for the first time the fabrication of metal–semiconductor–metal ultraviolet photodetector based on catalyst-free growth of ZnO nanowire networks on ITO seeds/glass substrates by thermal evaporation method. The morphological, structural, and optical properties of the sample were studied by using field emission scanning electron microscopy, X-ray diffraction, photoluminescence, and UV–Vis spectrophotometer. Upon exposure to 365 nm light (1.5 mW/cm²) at five-bias voltage, the device showed 2.32 × 10³ sensitivity. In addition, the photocurrent was 1.79 × 10⁻⁴ A, and the internal gain of the photodetector was 24.2. The response and the recovery times were calculated to be 3.9 and 2.6 s, respectively, upon illumination to a pulse UV light (365 nm, 1.5 mW/cm²) at five-bias voltage. All of these results demonstrate that this high-quality detector can be a promising candidate as a low-cost UV photodetector for commercially integrated photoelectronic applications.     

AlN codoping and fabrication of ZnO homojunction by RF sputtering

The ZnO homojunction fabricated from undoped and 1 mol% AlN doped (codoped) ZnO targets by RF magnetron sputtering has been reported. The grown films on Si (100) substrate have been characterized by X-ray diffraction (XRD), Energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Photoluminescence (PL) and Hall measurements. The increase of d-space value (compared with unstressed bulk) found from XRD for AlN codoped ZnO film supports the formation of p-ZnO due to the N incorporation. The presence of N in the film has been confirmed by EDS and XPS analysis. Further, the p-conductivity in AlN codoped ZnO has been evidenced by low temperature PL (donor-acceptor-pair emission) and room temperature PL (red shift in near-band-edge emission). Hall measurement shows that 1 mol% AlN codoped ZnO has the hole concentration of 3.772 × 10¹⁹ cm⁻³. The fabricated homojunction with 1% AlN doped ZnO (p-type) and undoped ZnO (n-type) exhibits a typical rectification behavior with high breakdown voltage, and rectification ratio, 13.4. The junction parameters such as ideality factor, barrier height and series resistance have also been calculated for the fabricated p-n junction. The energy band diagram has been proposed for the fabricated homojunction.     

电喷雾和二步热处理制备无硬团聚纳米氧化锌

通过电喷雾和二步热处理法制备得到无硬团聚的ZnO纳米微粒, 为制备无硬团聚氧化物纳米粉体提供了一种新方法. 试验采用添加适量PVP的Zn(CH₃COO)₂·2H2O的乙醇溶液作为电喷雾液体, 经过锥形喷雾得到均匀的微米级小液滴. 干燥后的喷雾产物先后在氮气炉和空气炉中分别600℃和400℃保温1h进行二步热处理. SEM、XRD测试结果表明, 使用该方法制备得到的ZnO纳米微粒粒度均匀, 结晶完整, 无硬团聚, 具有六角纤锌矿结构.     

Flexible cellulose and ZnO hybrid nanocomposite and its UV sensing characteristics

Abstract

This paper reports the synthesis and UV sensing characteristics of a cellulose and ZnO hybrid nanocomposite (CEZOHN) prepared by exploiting the synergetic effects of ZnO functionality and the renewability of cellulose. Vertically aligned ZnO nanorods were grown well on a flexible cellulose film by direct ZnO seeding and hydrothermal growing processes. The ZnO nanorods have the wurtzite structure and an aspect ratio of 9 ~ 11. Photoresponse of the prepared CEZOHN was evaluated by measuring photocurrent under UV illumination. CEZOHN shows bi-directional, linear and fast photoresponse as a function of UV intensity. Electrode materials, light sources, repeatability, durability and flexibility of the prepared CEZOHN were tested and the photocurrent generation mechanism is discussed. The silver nanowire coating used for electrodes on CEZOHN is compatible with a transparent UV sensor. The prepared CEZOHN is flexible, transparent and biocompatible, and hence can be used for flexible and wearable UV sensors.