Jun 2011, Volume 4 Issue 2

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    Mingwang SHAO
    Pijus Kanti SAMANTA, Partha Roy CHAUDHURI

    A simple wet chemical bath deposition has been successfully deployed to fabricate zinc oxide (ZnO) nanostructures. For substrate free growth, the nanostructure is spindle like monopods. But when the nanostructures grow on the glass and quartz substrates, they are bipods (two monopods joined together base to base). Variation in the size of the spindles of the monopods and bipods and the particle size was observed due to the strain exists in the thin film due to lattice mismatch at the interface of the thin film and the substrates. The X-ray diffraction (XRD) and selected area diffraction results confirmed the hexagonal unit cell structures of the monopods and bipods. Also the growth rates of various planes are different and the growth is anisotropic. The substrate free grown monopods show visible photoluminescence (PL) at 421 nm. But the emission gets shifted by 3 and 6 nm for ZnO thin film deposited on quartz and glass substrates respectively due to interfacial strain. In case of ZnO on quartz substrate a strong ultra-violet (UV) peak was observed at 386 nm due to band edge transition. These emissions are also accompanied by few weaker emission peaks due to various defect related transition.

    Haixin WU, Youbao NI, Chen LIN, Mingsheng MAO, Ganchao CHENG, Zhenyou WANG

    Single crystals of AgGaGeS4 (AGGS) were grown in a modified Bridgman furnace with 25 mm in diameter and 70 mm in length. The transmission spectra of as-grown AGGS slices were measured on a Hitachi 270-30 spectrophotometer, the fabricated device crystal was 5 mm×5 mm×3.5 mm in dimension and its absorption was 0.04–0.15 cm-1. Frequency doubling of 2.79 and 8 μm laser radiation were investigated using fabricated device crystals with thicknesses of 3.5 and 2.7 mm respectively.

    Youbao NI, Haixin WU, Mingsheng MAO, Chen LIN, Ganchao CHENG, Zhenyou WANG

    Single crystals of CdSe were grown by using seeded oriented temperature gradient solution zoning (S-TGSZ) method with the sizes of 20 mm in diameter and 80 mm in length. The crystals were characterized with X-ray diffraction, transmission spectrophotometer and infrared microscope. The transmission spectra showed that the infrared transmission is above 65% and the mean absorption was 0.01–0.04 cm-1 in the range of 2.5–20 μm. With 2.797 μm Cr,Er:YSGG laser as pumping source, experiments of optical parametric oscillator (OPO) were performed by using fabricated 5 mm×5 mm×30 mm device crystal. The signal and idler wavelengths and the output average power were respectively 4.3 μm, 8 μm and 400 μJ. Optical-to-optical conversion efficiency was obtained by 12%.

    Guangli WANG, Yi SHI, Lijia PAN, Lin PU, Jin LV, Rong ZHANG, Youdou ZHENG

    The Ge/Si nanocrystals on ultra thin high-k tunnel oxide Al2O3 were fabricated to form the charge trapping memory prototype with asymmetric tunnel barriers through combining the advanced atomic layer deposition (ALD) and pulse laser deposition (PLD) techniques. Charge storage characteristics in such memory structure have been investigated using capacitance-voltage (C-V) and capacitance-time (C-t) measurements. The results prove that both the two-layered and three-layered memory structures behave relatively qualified for the multi-level cell storage. The results also demonstrate that compared to electrons, holes reach a longer retention time even with an ultra thin tunnel oxide owing to the high band offset at the valence band between Ge and Si.

    Chuyan CHEN, Qing LI, Yiying WANG, Yuan LI, Xiaolin ZHONG

    Flower-like CuS nanostructures have been synthesized via a liquid precipitation route by the reaction between CuCl2·2H2O and thioacetamide (CH3CSNH2, TAA) in the ionic liquid 1-butyl-3-methyl imidazole six hexafluorophosphoric acid salts ([BMIM][PF6]) aqueous solution at room temperature. The products were characterized by X-ray powder diffraction (XRD), field emission scanning electronic microscopy (FESEM), Brunauer-Emmett-Teller (BET), Ultraviolet-Visible Spectrophotometer (UV-Vis) and Photoluminescence (PL) techniques. The as-prepared CuS nanostructures have a mean diameter of about 1 μm. A plausible mechanism was proposed to explain the formation of CuS nanostructures. The effects of experimental parameters on the formation of the products were also explored. With BET theory, it is found that the as-prepared CuS nanostructures have a specific area of 39 m2/g. The Barrett-Joyner-Halenda (BJH) pore size distribution of the as-prepared CuS nanostructures presents smaller pores centers about 60 nm. The UV-Vis and PL curves indicate that the as-prepared CuS nanostructures are promising candidates for the development of photoelectric devices.

    Caixia SONG, Yuwei SUN, Yaohua XU, Debao WANG

    A series of zinc oxide (ZnO) nano-/micro-rods had been synthesized via solution-based routes. In the hydrothermal route, the obtained ZnO nano-/micro-rods had two topographics. In refluxing procedures, spindly ZnO nanorods were obtained in the presence of poly(vinyl-pyrrolidone) (PVP) and ellipsoid-like nanorods were obtained in the absence of PVP. The products were characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and electron diffraction (ED) analysis. Room temperature photoluminescence (PL) spectra of the ZnO products demonstrated a weak UV emission and a broad visible emission for each of the sample. The growth mechanism of 1-D ZnO crystals was discussed briefly.

    Chunyan WU, Li WANG, Zihan ZHANG, Xiwei ZHANG, Qiang PENG, Jiajun CAI, Yongqiang YU, Huier GUO, Jiansheng JIE

    Sliver doped n-type CdS nanoribbons (NRs) were successfully synthesized by using Ag2S as the dopant via a thermal co-evaporation method. The CdS:Ag NRs have wurtzite single-crystal structure with growth direction of [110]. Significantly, the conductivity of the CdS NRs increased ~6 orders of magnitude by silver doping. Moreover, the Ag doped CdS NRs showed much enhanced photoconductivity compared with the undoped ones, which will greatly favor the application of CdS nanostructures in high-performance nano-optoelectronic devices.

    Zhiyong BAO, Li ZHANG, Yucheng WU

    Selective synthesis of silver and uniform single crystalline silver molybdate nanowires in large scale can be easily realized by a facile soft template approach. Ag6Mo10O33 nanowires with a uniform diameter of about 50 nm and the length up to several hundred micrometers were synthesized in large scale for the first time at room temperature using 12-silicotungstic acid system. The silver nanoparticles can be easily synthesized with the assistance of UV-light. Sensitive surface-enhanced Raman scattering signals of p-aminothiophenol were observed on Ag nanoparticles and silver molybdate nanowires complex. The results demonstrated that synthetic method could be a potential mild way to selectively synthesize various molybdate nanowires with various phases in large scale. The silver nanoparticles and silver molybdate nanowires complex would be proposed for surface-enhanced Raman scattering substrate.

    Yueyin SHAO, Yongqian WEI, Zhenghua WANG

    Silver modified silicon nanowires were obtained and employed as photo-catalysts in the degradation of Rhodamine B (RhB), which demonstrated the excellent catalytic activity. These catalysts may be recycled and reused.

    Ronghui QUE

    Large-scale, high-purity and uniform silver orthophosphate (Ag3PO4) nanowires had been synthesized by a facile hydrothermal method without employing any surfactants or templates for the first time. The nanowires were single-crystalline with lengths up to several micrometers. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy were used to characterize the morphology and structure of the as-prepared products. The as-prepared Ag3PO4 nanowires exhibited linear current-voltage (I-V) characteristics and excellent photoresponse. As the light was switched on and off, the currents could be reversibly switched between high and low value at the voltage of 0.1 V, which will find wide application in optoelectronic nanodevices.

    Yanhua TONG, Feng CAO, Peisong TANG, Haifeng CHEN, Guoxiang PAN, Minhong XU

    Hierarchical zinc oxide (ZnO) quasi-spheres consisting of nanoparticles with diameter of about 20 nm were synthesized via a one-pot reaction. The size of ZnO quasi-spheres is easily tunable from 80 nm to 3 μm by varying the type of zinc source and its concentration. The three samples 1-3 with the diameter of 80-180 nm, 300-600 nm and 1.2-2.9 μm were selected for fabricating dye-sensitized solar cells (DSSCs) and their photovoltaic properties were measured. The results demonstrate that DSSCs fabricated by sample 2 with the diameter within the wavelength of visible light obtain the highest short-circuit current density and over light conversion efficiency, due to resonant scattering increasing the photon absorption.

    Zhenghua WANG, Shiyu ZHU

    Trigonal selenium (t-Se) nanowires with uniform sizes were obtained through the conversion from freshly prepared amorphous selenium (a-Se) nanoparticles in acetone at room temperature. The experimental results show that some organic solvents, such as acetone and pyridine can dramatically promote the conversion from a-Se to t-Se, and t-Se with different morphologies like nanowires and microrods can be obtained. Acetone is an appropriate medium for obtaining t-Se nanowires in a short time. The as-prepared t-Se nanowires were characterized and confirmed by means of powder X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The photoelectrical properties of t-Se nanowires were investigated, which shows their potential uses in the fabrication of micro-devices or photo-switches.

    Qi SHAO, Tao WANG, Xiuhua WANG, Youcun CHEN

    Bis-(8-hydroxyquinoline) copper nanoribbons with an average width of 400 nm, a thickness of 70 nm and the length of up to tens of micrometers, were synthesized by a facile solvothermal method. X-ray powder diffraction and Fourier transform infrared spectrum were employed to determine their structure. The photoconductivity of a bundle of nanoribbons was also measured, which exhibited unique photoresponse to light, indicating their potential applications in photoswitch nanodevices in the future.

    Li LIU, Ze ZHANG

    One-dimensional (1D) organic nanoribbons built on N-p-nitrophenylsalicylaldimine cadmium complex were synthesized via a facile solvothermal route. Scanning electron microscope images revealed that the as-synthesized products were ribbon like with widths of 500 nm, thicknesses of about 50 nm, and lengthes up to several hundred micrometers. Fourier transform infrared spectrum was employed to characterize the structure. The conductivity of a bundle of nanoribbons was also measured, which showed that Schiff base cadmium nanoribbons had good photoconductive property. This work might enrich organic photoconductive materials and be applicable in nano photoswitch devices in the future.

    Jinjie CHEN, Bo LIU, Hao ZHANG

    The current status of the fiber Bragg grating (FBG) sensor technology was reviewed. Owing to their salient advantages, including immunity to electromagnetic interference, lightweight, compact size, high sensitivity, large operation bandwidth, and ideal multiplexing capability, FBG sensors have attracted considerable interest in the past three decades. Among these sensing physical quantities, temperature and strain are the most widely investigated ones. In this paper, the sensing principle of FBG sensors was briefly introduced first. Then, we reviewed the status of research and applications of FBG sensors. As very important for industrial applications, multiplexing and networking of FBG sensors had been introduced briefly. Moreover, as a key technology, the wavelength interrogation methods were also reviewed carefully. Finally, we analyzed the problems encountered in engineering applications and gave a general review on the development of interrogation methods of FBG sensor.

    Hui LI, Haobo CHENG, Yunpeng FENG, H. Y. TAM, Yongfu WEN

    Electrorheological (ER) finishing is a promising technique for polishing optical mirrors lenses. Silicone oil-based ER finishing fluid with ceria particles as abrasive was developed, whose dispersed phase was alumina, titanium dioxide, silica, and starch, respectively. Experiments were performed in detail under the voltage of 3000 V, after 25 min of polishing a K9 glass. By using the ER fluid developed in this paper, with 47.62% starch, 47.62% silicone oil, and 4.76% ceria, the surface roughness of the K9 glass was reduced from 8.46 nm Ra to 3.45 nm Ra. The result verifies the validity of the developed ER fluid.

    Kang YANG, Minming ZHANG, Deming LIU, Lei DENG

    This paper presents a scalable and cost-effective hybrid time division multiplexing (TDM)/wavelength division multiplexing (WDM) passive optical network (PON), in which reflective semiconductor optical amplifiers (RSOAs) are used as optical network units (ONUs) and a shared tunable laser and photoreceiver stack locate at the optical line terminal (OLT). Especially, tunable transmitters are not only shared by all ONUs, but also used for both upstream and downstream transmissions. To solve resource contention problem and provide efficient bidirectional communications between the OLT and the ONUs, two novel algorithms are proposed to manipulate the wavelength accessibility and the burst scheduling. The performance of both algorithms in terms of the average packet end-to-end delay and throughput were simulated and evaluated.

    Yimei HUANG, Hongqin YANG, Yuhua WANG, Shusen XIE, Zhouyi GUO, Songhao LIU

    Effective attenuation coefficients and diffuse reflectance spectra of acupuncture point and non-acupuncture point were measured in vivo before and after the brachial artery was constricted with a sphygmomanometer. Experimental results showed that the effective attenuation coefficient of acupuncture point was smaller than that of non-acupuncture point. When the brachial artery was constricted, the effective attenuation coefficients of acupuncture point and non-acupuncture point increased. Furthermore, the increasing amplitude of effective attenuation coefficient of acupuncture point was smaller than that of the non-acupuncture point. Diffuse reflectance of acupuncture point was lower than that of non-acupuncture point within the wavelength range of 470 to 600 nm. Both the diffuse reflectance of acupuncture point and non-acupuncture point decreased after the brachial artery was constricted. These experimental results indicated that the optical characteristics of acupuncture point tissues were correlated with the physiologic changes. Therefore, these optical characteristics of acupuncture points would be helpful to study the mechanism of acupuncture meridian.