Sputter deposited ZnO nanowires/thin film structures on glass substrate

Integrated ZnO nanowires/thin film structures were grown using radio-frequency magnetron sputter deposition on amorphous glass substrates having an electroless plated copper surface layer. The growth took place under different deposition times and O₂/Ar ratios. The substrate was not heated or biased during the deposition. Regardless of the O₂/Ar ratio, both nanowires and the film grew simultaneously. However, the growth of the nanowires and the film was diffusion-controlled and reaction-controlled, respectively. On the other hand, the O₂/Ar ratio substantially affected the crystal structure and morphology of the resulting ZnO deposits.     

UV photoconductivity characteristics of ZnO nanowire field effect transistor treated by proton irradiation

We investigated the UV photoconductivity characteristics of ZnO nanowire field effect transistors (FETs) irradiated by proton beams. After proton beam irradiation (using a beam energy of 10 MeV and a fluence of 10¹² cm^− 2), the drain current and carrier density in the ZnO nanowire FETs decreased, and the threshold voltage shifted to the positive gate bias direction due to the creation of interface traps at the SiO₂/ZnO nanowire interface by the proton beam. The interface traps produced a higher surface barrier potential and a larger depletion region at the ZnO nanowire surface, affecting the photoconductivity and its decay time. The UV photoconductivity of the proton-irradiated ZnO nanowire FETs was higher and more prolonged than that of the pristine ZnO nanowire FETs. The results extend our understanding of the UV photoconductivity characteristics of ZnO nanowire devices and other materials when irradiated with highly energetic particles.     

A high photocurrent gain in UV photodetector based on Cu doped ZnO nanorods on PEN substrate

Vertical well-aligned Cu-doped ZnO nanorods were successfully synthesized by chemical bath deposition (CBD) method on low cost and flexible polyethylene naphthalate (PEN) substrate. The structural and optical investigations exhibited the high quality of the Cu-doped ZnO nanorods on a flexible PEN substrate. The metal-semiconductor-metal (MSM) configuration was used to fabricate UV photodetector based on the Cu-doped ZnO nanorods grown on PEN substrate. Under a 5 V applied bias, the values of dark current and photocurrent of the Cu-doped ZnO nanorods photodetector were 14.9 µA and 3.27 mA, respectively. Meanwhile, calculated photocurrent gain of the UV photodetector was 219 at 5 V bias voltage. Upon exposure to 365 nm UV light, the UV device exhibited fast response time and recovery time of 0.317 and 0.212 s, respectively, at a bias voltage of 5 V.     

Synthesis of ZnO nanowire array film on Mg doped gallium nitride substrate

ZnO nanowire array films, composed of well aligned ZnO nanowires ～200?nm in diameter and 1?μm in length, were successfully synthesised on Mg doped gallium nitride by hydrothermal method. In addition, the films possess quite flatten surface. In the synthesised process, there was no catalyst that had been used. Growth conditions were comprehensively discussed in the process of aqueous solution method. It was found that the length of ZnO nanowires and the thickness of the film could be tunable by altering solution concentration and growth time. Such ZnO film assembled with vertically aligned nanowire may have potential applications as UV light emitting diodes.     

Effects of surface modification of the individual ZnO nanowire with oxygen plasma treatment

This study examined the effects of an oxygen plasma treatment on the properties of ZnO nanowires with diameters of 80 nm using a single nanowire field effect transistor. After the oxygen plasma treatment, the carrier concentration and mobility of individual ZnO nanowires decreased with a substantial positive shift in the threshold voltage. The shifting was accounted to the surface modification, resulted to the improved gas sensitivity under hydrogen gas exposure and an enhanced photocurrent response time in ultraviolet illumination. The plausible surface mechanisms responsible for these significant changes after the surface modification were suggested by considering the surface analysis and electrical transport mechanism.     

用于紫外光电导探测器的TiO2薄膜研究

采用直流反应磁控溅射的方法,制备了TiO2薄膜。用X射线衍射,原子力显微镜(AFM)和紫外-可见光分光光度计分别测试了TiO2薄膜的晶体结构、表面形貌及其紫外-可见光吸收谱,采用C／TiO2／ITO三层结构制备了TiO2光电导型紫外探测器,研究了它的光响应。初步实验结果表明：TiO2薄膜在4W的紫光灯辐射下,光电流可达2．1mA,10min的辐射时间内,光电流基本保持稳定,可见TiO2薄膜对紫外光有较高的灵敏度和稳定性,可作为一种良好的紫外光探测材料。     

ZnO纳米线阵列的图形化生长

采用光刻和射频磁控溅射技术在Si衬底上制备了图形化的ZnO种子层薄膜。分别采用气相榆运和水热合成法，制备了最小单元为30μm的图形化的ZnO纳米线阵列。X射线衍射（XRD）分析显示单晶纳米线阵列具有高度的c轴[001]择优取向生长性质，从扫描电子显微镜（SEM）照片看出，阵列图形完整清晰，边缘整齐，纳米线阵列在室温下光致发光（PL）谱线中在380hm左右具有强烈的紫外发射峰，可见光区域发射峰得到了抑制，证明ZnO纳米线阵列氧空位缺陷少，晶体质量高。     

Self-powered, ultrafast, visible-blind UV detection and optical logical operation based on ZnO/GaN nanoscale p-n junctions

Ultrafast-response (20 μs) UV detectors, which are visible-blind and self-powered, in devices where an n-type ZnO nanowire partially lies on a p-type GaN film, are demonstrated. Moreover, a CdSe-nanowire red-light detector powered by a nanoscale ZnO/GaN photovoltaic cell is also demonstrated, which extends the device function to a selective multiwavelength photodetector and shows the function of an optical logical AND gate.     

Fabrication and characterization of Ga-doped ZnO nanowire gas sensor for the detection of CO

We demonstrate an efficient CO sensor using Ga-doped ZnO (GZO) nanowires (NWs). Various GZO NWs are synthesized with Au catalysts on sapphire substrates by hot-walled pulse laser deposition. The deposition temperature of ZnO NWs was in the range of 800-900 °C. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) characterizations indicate that the obtained NWs have the well-crystallized hexagonal structure with customized Ga-doping concentration of 0-5 wt.%. The NWs have the diameter of about 50 nm and the length of about 8 µm. After depositing the Ag electrodes on both sides of the NW cluster, the resistance change is checked with the exposure to CO gas in the self-designed gas chamber that can facilitate the detection of the resistance change and the control of gas flow as well as temperature. The detected resistance modulations are 1.0 kΩ and 83.2 kΩ in the cases of 3 wt.% GZO and pure ZnO NW clusters, respectively, indication that we successfully customize the sensitivity of the gas sensors by controlled doping.     

Characterization of ZnO nanowires grown on Si (100) with and without Au catalyst

ZnO nanowires were grown on Si (100) substrates with and without Au catalyst by chemical vapor deposition employing the vapor-liquid-solid (VLS) and vapor-solid (VS) mechanisms, respectively. The diameters of the resulting nanowires were in the range 80-150 nm with typical length about 10 μm. The near-band-edge (NBE) emission of ZnO nanowires grown with and without catalyst was observed at 382 nm and 386 nm, respectively. The intensity of the NBE emission of ZnO nanowires grown without the catalyst was higher than that of the green luminescence. By sharp contrast, the intensity of the NBE emission of ZnO nanowires grown with catalyst was lower than that of green luminescence. The X-ray diffraction (XRD) spectrum of the ZnO nanowires grown without catalyst exhibited a peak intensity of c-plane 5 times higher than that of m-plane and 10 times higher than that of a-plane. However, the XRD spectrum of the ZnO nanowires grown with catalyst exhibited a peak intensity of the c-plane about 1.5 times higher than that of the m-plane and 4 times higher than that of a-plane intensity. Thus, the ZnO nanowires grown without catalyst have a preferential orientation along the c-axis direction. Our results show that the catalyst strongly effects optical and structural properties of the ZnO nanowires.     

High-strain sensors based on ZnO nanowire/polystyrene hybridized flexible films

A type of strain sensor with high tolerable strain based on a ZnO nanowires/polystyrene nanofibers hybrid structure on a polydimethylsiloxane film is reported. The novel strain sensor can measure and withstand high strain and demonstrates good performance on rapid human-motion measurements. In addition, the device could be driven by solar cells. The results indicate that the device has potential applications as an outdoor sensor system.     

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。     

Fabrication and Characterization of Undoped and Cobalt-doped ZnO Based UV Photodetector Prepared by RF-sputtering

Undoped and 1 at.% Co-doped ZnO nanostructure based UV photodetectors were successfully fabricated by RF- magnetron sputtering technique with comb like Pt electrodes. Cobalt ions were successfully incorporated into the lattice of the ZnO nanostructure without changing its wurtzite structure. It was indicated that Co-doping can effectively adjust the luminescence properties of the ZnO nanostructure. The undoped and Co-doped ZnO photodetectors were observed to have photosensitivities of 1.44 x 104 % and 8.57 x 102 % and low dark currents of 9.74 x 10-8 A and 1.18 x 10-7 A, respectively.     

衬底温度对磁控溅射制备外延ZnO薄膜结构特性的影响

在不同的衬底温度下,采用磁控溅射方法在蓝宝石(0001)衬底上制备了外延生长的ZnO薄膜.采用原子力显微镜(AFM)、X射线衍射仪(XRD)、可见-紫外分光光度计系统研究了衬底温度对ZnO薄膜微观结构和光学特性的影响.AFM结果表明在不同村底温度制备的ZnO薄膜具有较为均匀的ZnO晶粒,且晶粒的尺寸随衬底温度的增加逐渐增大.XRD结果显示不同温度生长的ZnO薄膜均为外延生长,400℃生长的薄膜具有最好的结晶质量;光学透射谱显示在370nm附近均出现一个较陡的吸收边,表明制备的ZnO薄膜具有较高的质量,其光学能带隙随着衬底温度的增加而减小.     

A novel, substrate independent three-step process for the growth of uniform ZnO nanorod arrays

We report a three-step deposition process for uniform arrays of ZnO nanorods, involving chemical bath deposition of aligned seed layers followed by nanorod nucleation sites and subsequent vapour phase transport growth of nanorods. This combines chemical bath deposition techniques, which enable substrate independent seeding and nucleation site generation with vapour phase transport growth of high crystalline and optical quality ZnO nanorod arrays. Our data indicate that the three-step process produces uniform nanorod arrays with narrow and rather monodisperse rod diameters (∼ 70 nm) across substrates of centimetre dimensions. X-ray photoelectron spectroscopy, scanning electron microscopy and X-ray diffraction were used to study the growth mechanism and characterise the nanostructures.     

Influence of substrate temperature and Zn-precursors on atomic layer deposition of polycrystalline ZnO films on glass

Influence of substrate temperature and Zn-precursors on growth rate, crystal structure, and electrical property of undoped ZnO thin films grown by atomic layer deposition (ALD) have been studied. Differences between dimethylzinc (DMeZn) and diethylzinc (DEtZn) used as Zn-precursors were examined. The ZnO films grown using DMeZn showed higher electrical resistivity compared to that grown using DEtZn. However, the higher resistivity in the case of DMeZn was owing to much amount of residual impurities incorporated during the ALD growth.     

纳米ZnO/CeO2抗紫外剂制备工艺研究

以Zn(NO3)2·6H2O、Ce(NO3)3·6H3O、(NH4)2CO3·H2O和PEG400为原料,采用直接沉淀法制备ZnO/CeO2抗紫外剂复合粉体,用XRD测试了纳米颗粒的粒径,研究了n(Zn2+)/n(Ce4+)、PEG400的用量、煅烧温度的最佳工艺,结果表明n(Zn2+)/n(Ce4+)为1∶3、PEG400用量为3mL、煅烧温度为500℃时效果最佳.     

ZnMgO基紫外探测器的研究进展及分析

ZnO基三元合金半导体材料因其重要的带隙调制作用,已成为紫外探测器发展的一个重要方向,特别是Zn_(1-x)Mg_xO基紫外探测器,可以探测日盲区紫外光,更是受到了各国极大的关注.当前,Zn_(1-x)Mg_xO基紫外探测器大多采用MSM叉指结构,响应峰位于300nm附近,响应时间最高可达ns量级,紫外可见光抑制比亦可大于4个数量级.扼要介绍了国内外相关小组的研究进展,并着重分析了薄膜组分、结构以及探测器性能参数等.     

AZO晶种层对ZnO纳米线生长及紫外光电导性能的影响

采用溶液化学法实现了在Zn(NO3)2/C6H12N4混合溶液中ZnO纳米线在AZO薄膜修饰过衬底上生长。AZO薄膜由射频磁控溅射法制备,通过溅射时间和基底温度的变化改变薄膜形态,重点研究了不同薄膜形态对ZnO纳米线形貌和结构的影响,最终在溅射2h、基底温度250℃晶种上得到垂直于衬底、高度平行取向的ZnO纳米线阵列。在此基础上研究了不同形貌ZnO纳米线阵列的紫外光电导性能差异。结果表明,垂直生长的纳米线较倒伏纳米线紫外响应迅速,分析认为是紫外光照下曝光面积不同造成的。     

ZnO nanowire growth by electric current heating method: A study on the effect of substrate temperature

In this study, we report the growth of ZnO nanowire on quartz glass substrates with Au-catalyst assistance by electric current heating of ZnO ceramic bar. The effect of substrate temperature on the properties of ZnO nanostructures has been investigated systematically. Structural analysis indicates that the grown ZnO crystals belong to hexagonal phase with preferential growth along (0 0 2) orientation. Scanning electron microscopic studies reveal the aligned ZnO nanowires were grown at 800 °C. The typical length and diameter of nanowires are in the uniform ranges of 4–20 μm and 20–100 nm, respectively, showing their high aspect ratio of about 1000. We have made an attempt to discuss about the change in ZnO nanostructures with different substrate temperatures and the possible mechanism for the growth of nanowires. Optical reflectance studies show the infrared reflectivity was controlled through the substrate temperature.