Self-Assembled Al Nanostructure/ZnO Quantum Dot Heterostructures for High Responsivity and Fast UV Photodetector

Light confinement induced by spontaneous near-surface resonance is inherently determined by the location and geometry of metallic nanostructures(NSs),offering a facile and effective approach to break through the limitation of the light-mater interaction within the photoactive layers.Here,we demonstrate high-performance Al NS/ZnO quantum dots(Al/ZnO) heterostructure UV photodetectors with controllable morphologies of the self-assembled Al NSs.The Al/ZnO heterostructures exhibit a superior light utilization than the ZnO/Al heterostructures,and a strong morphological dependence of the Al NSs on the optical properties of the heterostructures.The inter-diffusion of Al atoms into ZnO matrixes is of a great benefit for the carrier transportation.Consequently,the optimal photocurrent of the Al/ZnO heterostructure photodetectors is significantly increased by 275 times to ~1.065 mA compared to that of the pristine ZnO device,and an outstanding photoresponsivity of 11.98 A W-1 is correspondingly achieved under 6.9 MW cm-2 UV light illumination at 10 V bias.In addition,a relatively fast response is similarly witnessed with the Al/ZnO devices,paving a path to fabricate the high-performance UV photodetectors for applications.

Femtosecond pulse laser-induced self-organized nanostructures on the surface of ZnO crystal

This paper reports self-organized nanostructures observed on the surface of ZnO crystal after irradiation by a focused beam of a femtosecond Ti：sapphire laser with a repetition rate of 250kHz. For a linearly polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was promoted. The period of self-organization structures is about 180 nm. The grating orientation is adjusted by the laser polarization direction. A long range Bragglike grating is formed by moving the sample at a speed of 10μm/s. For a circularly polarized laser beam, uniform spherical nanoparticles were formed as a result of Coulomb explosion during the interaction of near-infrared laser with ZnO crystal.

Synthesis and characterization of ZnO nanostructures prepared by a thermal evaporation process

A series of ZnO nanostructures such as nanowires,nanobelts,nanocombs and mesoporous nanoballs were fabricated by a simple carbon reduction method without catalyst.The morphologies and microstructures of all samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and energy dispersive X-ray spectroscopy.The results indicate that different deposition temperatures have great impact on different shapes of ZnO nanostructures.The growth mechanisms of these ZnO nanostructrues suggest that,by controlling the experiment parameters,different morphological configurations nanostructures can be fabricated.

Rice Husk Templated Mesoporous ZnO Nanostructures for Ethanol Sensing at Room Temperature

Mesoporous zinc oxide nanostructures are successfully synthesized via the sol-gel route by using a rice husk as the template for ethanol sensing at room temperature. The structure and morphology of the nanostructures are characterized by x-ray diffraction, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and nitrogen adsorption-desorption analyses. The mechanism for the growth of zinc oxide nanostructures over the biotemplate is proposed. SEM and TEM observations also reveal the formation of spherical zinc oxide nanoparticles over the interwoven fibrous network. Multiple sized pores having pore diameter ranging from 10- 4Ohm is also evidenced from the pore size distribution plot. The larger surface area and porous nature of the material lead to high sensitivity （40.93% for 300 ppm of ethanol）, quick response （42s） and recovery （40 s） towards ethanol at 30014. The porous nature of the interwoven fibre-like network affords mass transportation of ethanol vapor, which results in faster surface accessibility, and hence it acts as a potential candidate for ethanol sensing at room temperature.

Controlling Growth of ZnO Nanostructures Via A Solution Route

A solution method was developed for fabricating ZnO nanostructures using （NH4）2CO3 as starting material SEM analysis shows that ZnO nanostructures exhibit nanorod, branch and flower-like morphologies. The crystal phase of as-synthesized products was characterized by X-ray diffraction （XRD）. The growth process, formation mechanism and optical property were also discussed by means of transmission electronic microscopy （TEM）, high resolution transmission microscopy （HRTEM） and photoluminescence （PL）. The growth direction of ZnO nanostructures was investigated based on the results of HRTEM. The PL spectrum shows two strong peaks （centered at around -387 and -470 nm） and a broad Deak （centered at around -580 nm）.

Synthesis and Optical Property Study on ZnO Nanostructures Via Vapor Phase Growth

Nanostructural zinc oxide films have been synthesized via vapor phase growthby heating pure zinc powder. Scanning electron microscopy ( SEM) images and X-ray diffraction (XRD)results showed that four kinds of morphologies ZnO nanostructures namely nanowires, well-alignednanorods, nanofeathers and hexagonal nano-rods were formed and all of wurtzite structural crystals.The results indicated that the temperature and substrate play an important role in the formation ofdifferent morphologies of ZnO nanostructures. The photoluminescence (PL) measurement was carried outfor the well-aligned nanorods ZnO sample and blue emission peaks at 420 and 444 nm have beenobserved at room temperature. And the blue emission mechanism is discussed.

ZnO纳米结构薄膜的构建及气敏传感性能研究

针对ZnO气敏传感器灵敏度较低和响应恢复时间长的问题,采用磁控溅射法,通过调控生长条件,构建了具有纳米结构的ZnO薄膜,研究了不同生长条件下ZnO纳米结构薄膜的形貌、结晶取向及其气敏传感性能。结果表明:高生长速度和高温条件下容易生长为柱状晶体且具有(103)晶面择优取向结构的薄膜,其对乙醇的灵敏度较好,达到81.7。

Preparation and Characterization of Silver Doped ZnO Nanostructures

ZnO was prepared by hydrothermal method. The result of scanning electron microscopy showed that the materials had nano rod structures. Ag-doped ZnO was prepared by UV-photoreduction. Crystalline phases and optical absorption of the prepared Ag-doped ZnO samples were determined by X-ray diffraction, Raman spectrum, UV-visible, and UV- photoreduction spectrophotometer. X-ray analyses revealed that Ag was doped ZnO crystallizes in hexagonal wurtzite structure. The incorporation of Ag+ in the site of Zn2+ provoked an increase in the size of nanocrystals as compared to pure ZnO. The photocatalytic and photoluminescence properties of materials were considered.

Growth and Improvement of ZnO Nanostructure Using Aged Solution by Flow Coating Process

ZnO nanostructures were prepared on corning glass substrate by flow coating process with different annealing temperature from 100?C to 600?C. Fresh and two days aged solutions were used to investigate the growth behavior and to evaluate the nanostructure of ZnO. The effect of preparation conditions on the deposition of ZnO nanostructure was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, and photoluminescence spectroscopy (PL). The results indicated that the solution aging condition and annealing temperature have a strong influence on the morphology and structural properties of the ZnO nanostructure. The solution aged after two days shows the different morphologies compared with the freshly prepared solution.

Modification at Lattice Scale for an Optimized Optical Response of Al_x(ZnO)_1-xNanostructures

We report the systematic changes of nano-scaled features and optical properties in a promising transparent oxide material, namely, Alx (x = 0, 1, 2 and 5%) doped ZnO1-x (AZO). Electron microscopy investigations revealed the alterations at lattice scale depending on the presence of Al-content in ZnO nanostructures. Lattice spacings of 0.26 and 0.28 nm oriented along the (0002) and (10 0) planes, respectively, were attributed to euhedral-and facetted-structures of hexagonal-ZnO. The AZO samples were further characterized by XRD, SEM, UV-vis spectrophotometry, Raman spectroscopy and photoluminescence studies. It has been shown that at a dopant concentration of 2%Al in ZnO, an optimal balance could be achieved between microstructure and optical properties.

Zinc Oxide Nanostructures for NO_2 Gas–Sensor Applications:A Review

Because of the interesting and multifunctional properties,recently,ZnO nanostructures are considered as excellent material for fabrication of highly sensitive and selective gas sensors.Thus,ZnO nanomaterials are widely used to fabricate efficient gas sensors for the detection of various hazardous and toxic gases.The presented review article is focusing on the recent developments of NO2gas sensors based on ZnO nanomaterials.The review presents the general introduction of some metal oxide nanomaterials for gas sensing application and finally focusing on the structure of ZnO and its gas sensing mechanisms.Basic gas sensing characteristics such as gas response,response time,recovery time,selectivity,detection limit,stability and recyclability,etc are also discussed in this article.Further,the utilization of various ZnO nanomaterials such as nanorods,nanowires,nano-micro flowers,quantum dots,thin films and nanosheets,etc for the fabrication of NO2gas sensors are also presented.Moreover,various factors such as NO2concentrations,annealing temperature,ZnO morphologies and particle sizes,relative humidity,operating temperatures which are affecting the NO2gas sensing properties are discussed in this review.Finally,the review article is concluded and future directions are presented.

Low-dimensional structures formed by irradiation of laser

Some kinds of low-dimensional nanostructures can be formed by irradiation of laser on the pure silicon sample and the SiGe alloy sample. This paper has studied the photoluminescence （PL） of the hole-net structure of silicon and the porous structure of SiGe where the PL intensity at 706nm and 725nm wavelength increases obviously. The effect of intensity-enhancing in the PL peaks cannot be explained within the quantum confinement alone. A mechanism for increasing PL emission in the above structures is proposed, in which the trap states of the interface between SiO2 and nanocrystal play an important role.

Zinc Oxide Nanostructured Biosensor for Glucose Detection

Zinc oxide （ZnO） nanocombs were fabricated by vapor phase transport, and nanorods and hierarchical nanodisk structures by aqueous thermal decomposition. Glucose biosensors were constructed using these ZnO nanostructures as supporting materials for glucose oxidase （GOX） loading. These ZnO glucose biosensors showed a high sensitivity for glucose detection and high affinity of GOX to glucose as well as the low detection limit. The results demonstrate that ZnO nanostructures have potential applications in biosensors.

Zinc Oxide Nanostructure Thick Films as H₂S Gas Sensors at Room Temperature

The ZnO nanostructures have been synthesized and studied as the sensing element for the detection of H2S. The ZnO nanostructures were synthesized by hydrothermal method followed by sonication for different interval of time i.e. 30, 60, 90 and 120 min. By using screen printing method, thick films of synthesized ZnO nanostructure were deposited on glass substrate. Gas sensing properties of ZnO nanostructure thick films were studied for low concentration H2S gas at room temperature. The effects of morphology of synthesized ZnO nanostructure on gas sensing properties were studied and discussed. ZnO nanostructure synthesized by this method can be used as a promising material for semiconductor gas sensor to detect poisonous gas like H2S at room temperature with high sensitivity and selectivity.

Field Emission Characterization of 1D-Nanostructural ZnO Grown at Low Temperature

By heating pure zinc powder at low tenlperature, two kinds of ZnO nanostructures with different mor phology and diameter were grown on silicon （100） substrates. Scanning electron microscopy images show that ZnO nanorods and ZnO nanowires have been obtained. XRD dem onstrates that the grown ZnO nanostructures are hexagonal wurtzite crystalline. The electron field emission properties were studied for both kinds of samples. The ZnO nanorods sample has a low turn-on field at 3.6 V/μm owing to better alignment, while the field to obtain a current density of 1mA·cm^-2 is higher （at 11. 2 V/μm） than that of the nanowires sample due to bigger diameter. For nanowires sampie, an emission current of 1 mA·cm^-2 is achieved at 8.2 V/μm which is Lower than that of ZnO nanorods owing to belier high aspect ratio.

Structural,Morphological and Electrical Properties of In-Doped Zinc Oxide Nanostructure Thin Films Grown on p-Type Gallium Nitride by Simultaneous Radio-Frequency Direct-Current Magnetron Co-Sputtering

Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.

Preparation,Properties,and Applications of Low-Dimensional Molecular Organic Nanomaterials

In recent years, great progress has been made in research and development of small-molecule organic materials with various low-dimensional nanostructures. This paper presents a comprehensive review of recent research progress in this field, including preparation, electronic and optoelectronic properties and applications. First, an introduction gives to the reprecipitation, soft templates methods, and progress in synthesis and morphological control of low-dimensional small-molecule organic nanomaterials. Their unique optical and electronic properties and research progress in these aspects are reviewed and discussed in detail. Applications based on low-dimensional small-molecule organic nanomaterials are briefly described. Finally, some perspectives to the future development of this field are addressed.

纳米ZnO的研究及其进展

纳米ZnO的许多优异性能使其成为人们研究的热点并得到广泛的应用.随着ZnO颗粒尺度的不断减小,其量子限域效应越来越明显,观察到电荷载流子,声子,光子的局域化效应;表面、界面态对其性质影响逐渐明显,通过表面修饰和置入多孔及束管等束缚结构,可有效增强ZnO紫外(一个量级)或可见光区(1-2个量级)的发射强度;并使ZnO的电导率,磁化率有很大提高.纳米ZnO与其他材料的复合体系能得到一些新的功能材料.纳米ZnO的自组织行为,使人们可以获得许多形态各异,特殊用途的纳米材料及器件.本文综述了近年来纳米ZnO的研究新动态.