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1.
Field ionization gas sensors based on ZnO nanorods (50–300 nm in diameter, and 3–8 μm in length) with and without a buffer layer were fabricated, and the influence of the orientation of nano-ZnO on the ionization response of devices was discussed, including the sensitivity and dynamic response of the ZnO nanorods with preferential orientation. The results indicated that ZnO nanorods as sensor anode could dramatically decrease the breakdown voltage. The XRD and SEM images illustrated that nano-ZnO with a ZnO buffer layer displayed high c-axis orientation, which helps to significantly reduce the breakdown voltage. Device A based on ZnO nanorods with a ZnO buffer layer could distinguish toluene and acetone. The dynamic responses of device A to the NO x compounds presented the sensitivity of 0.045 ± 0.007 ppm/pA and the response speed within 17–40 s, and indicated a linear relationship between NO x concentration and current response at low NO x concentrations. In addition, the dynamic responses to benzene, isopropyl alcohol, ethanol, and methanol reveals that the device has higher sensitivity to gas with larger static polarizability and lower ionization energy.  相似文献   

2.
冯秋菊  蒋俊岩  唐凯  吕佳音  刘洋  李荣  郭慧颖  徐坤  宋哲  李梦轲 《物理学报》2013,62(5):57802-057802
利用简单的化学气相沉积方法, 首先在n-Si衬底上生长Sb掺杂p-ZnO薄膜, 并在此基础上制作了p-ZnO/n-Si异质结发光二极管.对制备的Sb掺杂ZnO薄膜 在800 ℃下进行了热退火处理, 发现退火后样品的晶体质量和表面形貌都得到明显提高, 并且薄膜呈现的电导类型为p型, 载流子浓度为9.56× 1017 cm-3. 此外, 该器件还表现出良好的整流特性, 正向开启电压为4.0 V, 反向击穿电压为9.5 V. 在正向45 mA的注入电流条件下, 器件实现了室温下的电致发光. 这说明较高质量的ZnO薄膜也可以通过简单的化学气相沉积方法来实现, 这为ZnO基光电器件的材料制备提供了一种简单可行的方法. 关键词: CVD p-ZnO 异质结 电致发光  相似文献   

3.
We report fairly pure ultraviolet (UV) electroluminescence (EL) from a novel p-Si-based SiOx/ZnO/SiOx (< 2) double-barrier device. When the device is forward biased with positive voltage applied on the gate electrode of Au film, UV light originated from the near-band-edge emission of ZnO is dominant in the EL spectra, while the defect-related visible emissions are undetectable. In the case of reverse bias, no EL is detected from the device. The mechanisms of EL and carrier transports have been explained in terms of energy band structures under forward and reverse biases.  相似文献   

4.
Various metal-insulator-semiconductor (MIS) devices in the form of Au/SiOx(x<2)/Si, Au/AlOy(y<1.5)/Si, Au/SiOx/ZnO and Au/AlOy/ZnO have been fabricated. For each device, once a sufficiently high positive voltage is applied on the Au electrode, the same ultraviolet (UV) emission with a spectrum featuring several specific peaks is detected. Interestingly, such UV emissions related to the MIS devices originate from the external N2 microplasma. It is believed that at the high enough positive voltages the highly energetic electrons emitted out of the Au electrode activate the air to generate the N2 microplasma.  相似文献   

5.
In this study, Ag or Al-doped TiO2/ZnO heterostructure nanocatalysts were prepared using a sol-gel method for photocatalysis to evaluate the degradability. The photocatalytic behavior was evaluated by the degradation of methylene blue (MB) under ultraviolet (UV) light irradiation. Photocatalytic studies suggested that 1 mol% Ag-doped TiO2/ZnO (TiO2/ZnO = 0.75/0.25) heterostructure nanocatalysts showed higher photocatalytic activity, and that the degradation efficiency can reach 83% in 4 h, 14% higher than that for pure TiO2. Finally, the photocatalysis mechanism for the Ag-doped TiO2/ZnO heterostructure nanocatalysts is discussed.  相似文献   

6.
High-quality ZnO thin films were grown on single-crystalline Al2O3(0001) and amorphous SiO2/Si(100) substrates at 400–640 °C using laser molecular beam epitaxy. For film growth, the third harmonics of a pulsed Nd:YAG laser were illuminated on a ZnO target. The ZnO films were epitaxially grown on Al2O3(0001) with the narrow X-ray diffraction full width at half maximum (FWHM) of 0.04° and the films on SiO2/Si(100) exhibited a preferred c-axis orientation. Furthermore, the films exhibited excellent optical properties in photoluminescence (PL) measurements with very sharp excitonic and weak deep-level emission peaks. At 15 K, PL FWHM values of the films grown on Al2O3(0001) and SiO2/Si(100) were 3 and 18 meV, respectively. Received: 8 May 2001 / Accepted: 18 September 2001 / Published online: 20 December 2001  相似文献   

7.
Hybrid light emitting diodes (LEDs) based on zinc oxide (ZnO) nanorods and polymers (single and blended) were fabricated and characterized. The ZnO nanorods were grown by the chemical bath deposition method at 50°C. Three different LEDs, with blue emitting, orange-red emitting or their blended polymer together with ZnO nanorods, were fabricated and studied. The current–voltage characteristics show good diode behavior with an ideality factor in the range of 2.1 to 2.27 for all three devices. The electroluminescence spectrum (EL) of the blended device has an emission range from 450 nm to 750 nm, due to the intermixing of the blue emission generated by poly(9,9-dioctylfluorene) denoted as PFO with orange-red emission produced by poly(2-methoxy-5(20-ethyl-hexyloxy)-1,4-phenylenevinylene) 1,4-phenylenevinylene) symbolized as MEH PPV combined with the deep-band emission (DBE) of the ZnO nanorods, i.e. it covers the whole visible region and is manifested as white light. The CIE color coordinates showed bluish, orange-red and white emission from the PFO, MEH PPV and blended LEDs with ZnO nanorods, respectively. These results indicate that the choice of the polymer with proper concentration is critical to the emitted color in ZnO nanorods/p-organic polymer LEDs and careful design should be considered to obtain intrinsic white light sources.  相似文献   

8.
黄金昭  李世帅  冯秀鹏 《物理学报》2010,59(8):5839-5844
利用水热法制备了垂直于衬底的定向生长的ZnO纳米棒,利用扫描电子显微镜及光致发光的方法对其形貌及光学特性进行了表征,利用场发射性能测试装置对ZnO纳米棒的场发射性能进行了测试.结果表明:利用水热法在较低的温度(95 ℃) 下生长了具有较好形貌和结构的ZnO纳米棒,并表现出了较好的场发射特性,当电流密度为1 μA/cm2时,开启电场是2.8 V/μm,当电场为6.4 V/μm时,电流密度可以达到0.67 mA/cm2,场增强因子为3360.稳定性测试表明,在5 h内,4.5 V/μm的电场下,其波动不超过25%.将制备的ZnO纳米棒应用到有机/无机电致发光中,其中ZnO纳米棒为电子传输层,m-MTDATA(4,4',4″-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine) 为空穴传输层,得到了ZnO的342 nm的紫外电致发光,此发光较ZnO纳米棒光致发光的紫外发射有约40 nm的蓝移. 关键词: ZnO纳米棒 场发射 水热法 有机/无机复合电致发光  相似文献   

9.
《Current Applied Physics》2014,14(9):1171-1175
ZnO/WO3 core–shell nanowires were synthesized by thermal evaporation of a mixture of ZnO and graphite powders (ZnO:C = 1:1) followed by sputter-deposition of WO3. The sensing properties of multiple networked ZnO-core/WO3-shell nanorod sensors toward H2 gas was examined. The responses of pristine ZnO and ZnO-core/WO3-shell nanorods to 1000 ppm H2 at room temperature under UV illumination were ∼236% and ∼645%, respectively. The responses of the core–shell nanowires increased from ∼118 to ∼645% with increasing the UV illumination intensity from 0 mW/cm2 to 1.2 mW/cm2. The enhanced sensing performance of the ZnO-core/WO3-shell nanowires induced by encapsulation with WO3 was explained based on a combination of surface depletion and potential barrier-controlled carrier transport models. The origin of the enhanced sensing properties of ZnO-core/WO3-shell nanorods toward H2 under UV illumination was also discussed.  相似文献   

10.
Electrodeposition of ZnO nanorods for device application   总被引:1,自引:0,他引:1  
We report the electrochemical growth of zinc oxide nanorods in a zinc nitrate/hexamethylenetetramine solution at 70 °C. High-density vertical nanorods were grown on Au films on silicon substrates with a texture coefficient better than 99.9%. By varying the reactant concentration the diameter can be varied between 100 and 250 nm, with corresponding lengths of 1 to 4 μm. Furthermore, this approach was used for the selective growth on Ti/Au strip conductors ordered in an interdigitated structure on an insulating substrate. We achieved the growth of ZnO nanorods between neighbouring strip conductors bridging the gap between them. In this configuration the nanorods are already contacted and electrical measurements can be directly performed. First I–V measurements show a good conductivity of the as-grown nanorods and the resistance could be estimated to be 0.1 Ω cm. Under UV illumination the ZnO nanorods demonstrate a photoconductivity, but only after annealing the sample at 300 °C in N2. PACS 61.05.cp; 73.63.-b; 78.55.Et; 81.15.Pq; 82.45.Yz  相似文献   

11.
The formation and properties of radial heteroepitaxial ZnO/(Mg,Zn)O nanowires is reported in which the (Mg,Zn)O is cubic. Synthesis is achieved via a catalyst-driven molecular beam epitaxy technique. The nanowires were grown on Ag-coated Si substrates at growth temperatures ranging from Tg=300 to 500 °C, using Zn, Mg, and O3/O2 as the reactive flux. Structural and compositional analyses indicate that the core of the nanowire is ZnO possessing the hexagonal wurtzite structure, with the (Mg,Zn)O sheath assuming the cubic rock salt structure. Since (Mg,Zn)O has a larger band-gap energy (up to 7.8 eV) than that of ZnO (3.37 eV), these radial heterostructure nanorods provide an interesting system for quantum confinement and one-dimensional nanoscale device studies. PACS 81.05.Dz; 81.07.Vb  相似文献   

12.
通过溶胶凝胶(sol-gel)法分别在玻璃衬底上制备了ZnO纳米薄膜和ZnO-SiO2纳米复合薄膜,并利用紫外-可见光分光光度计对薄膜的光学性能进行了分析.可见光-紫外透射谱显示,随着ZnO溶胶浓度从0.7mol/L降低到0.006mol/L,制备的ZnO薄膜从只出现一个380nm(对应的光学禁带宽度为3.27eV)左右的吸收边到在380和320nm(对应的光学禁带宽度为3.76eV)左右各出现一个吸收边,并且随着ZnO溶胶浓度的降低,在380—320nm波段内的透过率明显提高.而Z 关键词: 纳米ZnO 2复合薄膜')" href="#">ZnO-SiO2复合薄膜 溶胶凝胶法 透射率  相似文献   

13.
We investigate, both experimentally and theoretically, current and capacitance (I–V/C–V) characteristics and the device performance of Si/SiO2/Si single-barrier varactor diodes (SBVs). Two diodes were fabricated with different SiO2 layer thicknesses using the state-of-the-art wafer bonding technique. The devices have very low leakage currents (about 5×10-2 and 1.8×10-2 mA/mm2) and intrinsic capacitance levels of typically 1.5 and 50 nF/mm2 for diodes with 5-nm and 20-nm oxide layers, respectively. With the present device physical parameters (25-mm2 device area, 760-μm modulation layer thickness and ≈1015-cm-3 doping level), the estimated cut-off frequency is about 5×107 Hz. With the physical parameters of the present existing III–V triplers, the cut-off frequency of our Si-based SBV can be as high as 0.5 THz. Received: 9 February 2001 / Accepted: 9 February 2001 / Published online: 23 March 2001  相似文献   

14.
The feasibility of a storage element with inherent rectifying or isolation properties for use in passive memory arrays has been demonstrated using a programmable metallization cell structure with a doped (n-type) silicon electrode. The Cu/Cu–SiO2/n-Si cell used in this study switches via the formation of a nanoscale Cu filament in the Cu–SiO2 film which results in the creation of a Cu/n-Si Schottky contact with soft reverse breakdown characteristics. The reverse bias leakage current in the on-state diode is dependent on the programming current employed as this influences the area of the electrodeposit and hence the area of the Cu/n-Si junction. The programming current also controls the on-state resistance of the device, allowing multi-level cell (MLC) operation, in which discrete resistance levels are used to represent multiple logical bits in each physical cell. The Cu/Cu–SiO2/n-Si elements with heavily doped silicon electrodes were readily erasable at voltage less than −5 V which allows them to be re-programmed. Lightly doped silicon electrode devices were not able to be erased due to their very high reverse breakdown voltage but exhibited extremely low leakage current levels potentially allowing them to be used in low energy one-time programmable arrays.  相似文献   

15.
M RIAZIAN  A BAHARI 《Pramana》2012,78(2):319-331
TiO2 Nano rods can be used as dye-sensitized solar cells, various sensors and photocatalysts. These nanorods are synthesized by a hydrothermal corrosion process in NaOH solution at 200°C using TiO2 powder as the source material. In the present work, the synthesis of TiO2 nanorods in anatase, rutile and Ti7O13 phases and synthesis of TiO2 nanorods by incorporating SiO2 dopant, using the sol–gel method and alkaline corrosion are reported. The morphologies and crystal structures of the TiO2 nanorods are characterized using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) study. The obtained results show not only an aggregation structure at high calcination temperatures with spherical particles but also Ti–O–Si bonds having four-fold coordination with oxygen in SiO4 − .  相似文献   

16.
The preferred (002) orientation zinc oxide (ZnO) nanocrystalline thin films have been deposited on FTO-coated glass substrates by sol–gel spin-coating technology and rapid thermal annealing for use in dye-sensitized solar cells (DSSC). The effects of preannealing temperature (100 and 300°C) on the microstructure, morphology and optical properties of ZnO thin films were studied. The ZnO thin films were characterized by X-ray diffraction (XRD), scanning electron microscopic (SEM) and Brunauer–Emmett–Teller (BET) analysis. The photoelectric performance of DSSC was studied by IV curve and the incident photon-to-current conversion efficiency (IPCE), respectively. From the results, the intensities of (002) peaks of ZnO thin films increases with increasing preannealing temperature from 100°C to 300°C. The increase in pore size and surface area of ZnO films crystallized at the increased preannealing temperature contributed to the improvement on the absorption of N3 dye onto the films, the short-circuit photocurrent (J sc) and open-circuit voltage (V oc) of DSSC. The higher efficiency (η) of 2.5% with J sc and V oc of 8.2 mA/cm2 and 0.64 V, respectively, was obtained by the ZnO film preannealed at 300°C.  相似文献   

17.
A memory device with In2O3 nanocrystals embedded in a biphenyl-tertracarboxylic dianhydride-phenylen diamine (BPDA-PDA) polyimide layer on a ZnO layer was fabricated, and its electrical properties were evaluated. Then, the transmittance efficiency in the structure of the BPDA-PDA polyimide/In2O3 nanocrystals/ZnO/ITO/double polishing sapphire substrate was measured to be about 80% between 440 to 800 nm by ultraviolet-visible transmittance spectroscopy. A bipolar switching current bistability by difference resistance appeared in the sweep voltage rage from −7 to 7 V. It was considered that the bipolar behavior of current-voltage may originate from a resistance fluctuation because of the electron charging effect in In2O3 nanocrystals by voltage sweeping, Fowler–Nordheim tunneling, space-charge-limited current, and the migration of O2− ions.  相似文献   

18.
采用溶胶-凝胶技术在玻璃衬底上制备了ZnO薄膜和ZnO-SiO2复合膜.原子力显微镜照片显示ZnO薄膜具有球状纳米晶粒;可见光-紫外透射光谱表明ZnO-SiO2复合膜在可见光区的透过率大约是85%,透过率从330 nm开始下降,到290 nm附近降为零.由于量子效应,吸收边出现明显的蓝移.在室温下用不同波长的光激发ZnO-SiO2复合膜,光致发光谱显示ZnO-SiO2复合膜对应于激子发射的290 nm附近的紫外发光峰与透射谱所显示的吸收边位置一致,没有出现斯托克斯红移.同时,ZnO-SiO2复合膜出现了双光子和三光子吸收现象和上转换发光现象. 关键词: 2')" href="#">ZnO-SiO2 量子效应 双光子和三光子吸收 上转换发光  相似文献   

19.
The effects of Si substrate orientation and surface treatment on the morphology and density of Zinc oxide (ZnO) nanorods were investigated. The size and density of ZnO nanorods were influenced by Si substrate orientation and surface preparation. ZnO nanorods synthesized on the ideally H-terminated Si(1 1 1) prepared with an NH4F solution resulted in the biggest size and the lowest density. It is suggested that the smoother surface of the Si substrate and lattice shape match with a larger atomic distance result in the increase of the ZnO seedlayer's grain size, which in turn enhances the size of ZnO nanorods grown on it. The optical properties of the ZnO nanorods were affected by their size and crystallinity. The smallest ZnO nanorods with a preferential c-axis orientation synthesized on the HF-treated Si(1 1 1) surface showed the highest intensity ratio of UV to visible emission, and the biggest ZnO nanorods synthesized on the N2-sparged NH4F-treated Si(1 1 1) surface showed the lowest intensity ratio of UV to visible emission. Therefore, it can be concluded that Si substrate orientation and surface preparation significantly affect the optical properties of ZnO nanorods.  相似文献   

20.
Copper doped ZnO nanoparticles were synthesized by a chemical technique based on a hydrothermal method. The crystallite sizes, estimated by XRD and TEM/SEM for different doping percentage of Cu2+ (1–10%), were found to be in the range of ~10–15 nm. TEM/SEM images showed formation of uniform nanorods, the aspect ratio of which varied with doping percentage. Photoluminescence (PL) measurement showed strong green visible emission and PL intensity was found enhanced with increase in doping percentage. The increase in the PL intensity was mainly due to Cu incorporation in ZnO lattice. Currently, light-emitting diodes (LEDs) giving ultraviolet emission have been combined with broad-band visible green phosphors to make white-light LEDs. Thus, green luminescent ZnO:Cu2+ nanoparticles are seen as necessary and condemnatory constituent for white-light generation from UV LEDs, underlying the importance of the current work.  相似文献   

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