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1.
The photoconductivity of pure and Cu-doped layered gallium monosulfide (GaS) single crystals, and of Ni-GaS(Cu)-In and GaS(Cu)-ZnO structures, is investigated. The activation energies of surface states were found as 0.10 eV, 0.40 eV and 17 meV, ∼400 meV for GaS and GaS(Cu), respectively. Cu acceptor levels are localized at 0.44 eV and 0.52 eV above the valence band of GaS. ZnO-GaS(Cu) heterojunctions show remarkable photosensitivity in the wavelength range of 250-700 nm. 相似文献
2.
Ge nanostructures were synthesized by reduction of GeO(2) in H(2) atmosphere at various temperatures. Entangled and straight Ge nanowires with oxide shells were grown at high temperatures. Ge nanowires with various numbers of nodules were obtained at low temperatures. Ge nanowires without nodules exhibited remarkable field emission properties with a turn-on field of 4.6 V μm(-1) and field enhancement factor of 1242. 相似文献
3.
Controlled synthesis and field emission properties of ZnO nanostructures with different morphologies
Huang YH Zhang Y Liu L Fan SS Wei Y He J 《Journal of nanoscience and nanotechnology》2006,6(3):787-790
By simply controlling atmosphere, rods, tetraleg-rods, and arrays of ZnO nanostructures have been fabricated respectively through pure zinc powder evaporation without catalyst at temperature of 650 - 700 degrees C. Investigations through HRTEM and XRD showed that the growth of the synthesized ZnO nanostructures was controlled by vapor-solid mechanism. Field emission measurements revealed that all of the structures, owing to their very low turn-on voltage, sufficient emission current and proper linearity of 1/V - Ln(l/V2), are likely to be potential candidates as a field emitter. The results also indicated that field emission properties are relative to morphology and size of the tips of ZnO nanostructures, and the nanorods with sharp tips possess the first-class FE property. 相似文献
4.
Hsueh TJ Hsu CL Chang SJ Lu CY Lin YR Chen IC 《Journal of nanoscience and nanotechnology》2007,7(3):1076-1079
Crabwise ZnO nanowires with an average length of 5 microm and an average diameter of 30 nm were selectively grown on ZnO:Ga/glass templates. Cathodoluminescence measurement indicated that the crystal quality of the crabwise ZnO nanowires was good. With an applied voltage of 120 V, the crabwise ZnO nanowire field emitters gave an emission current of 0.1 mA/cm2. Moreover, the field enhancement factor, beta, of the crabwise ZnO nanowires was approximately 980. 相似文献
5.
Guo Zhong Abul Kalam Ayed Sad Al-Shihri Qingmei Su Jie Li Gaohui Du 《Materials Research Bulletin》2012,47(6):1467-1470
We have grown large-scale well-aligned ZnO nanorods/nanowires on commercial flexible graphite sheet (FGS) at low temperature via chemical vapor deposition method. The products were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The effects of the growth temperature and oxygen flow rate on the morphology of ZnO nanostructures have been investigated. The growth mechanism of ZnO is found to be a self-catalytic vapor–solid process assisted by the immiscibility of ZnO with graphite. The as-grown ZnO/FGS products show strong green emission and their photoluminescence properties can be tuned by changing growth condition or annealing treatment. 相似文献
6.
A simple synthesis route to hierarchical ZnO arrays on zinc substrate in aqueous solution containing zinc nitrate and ammonia water was reported, without the assistance of any seeds, catalysts and surfactants. The as-prepared product consisted of very thin nanosheets attached onto the top of well-aligned nanorod arrays. A possible growth mechanism was proposed. The room-temperature photoluminescence spectrum showed UV emission around 398 nm and diverse visible emission peaks, indicating there might be a large concentration of oxygen defects in the sample. This method is both controllable and reproducible. 相似文献
7.
We demonstrated that the diameter and the density of carbon nanotubes (CNTs) which had a close relation to electric-field-screening effect could be easily changed by the control of catalytic Ni thickness combined with NH3 plasma pretreatment. Since the diameter and the density of CNTs had a tremendous impact on the field-emission characteristics, optimized thickness of catalyst and application of plasma pretreatment greatly improved the emission efficiency of CNTs. In the field emission test using diode-type configuration, well-dispersed thinner CNTs exhibited lower turn-on voltage and higher field enhancement factor than the densely-packed CNTs. A CNT film grown using a plasma-pretreated 25 angstroms-thick Ni catalyst showed excellent field emission characteristics with a very low turn-on field of 1.1 V/microm @ 10 microA/cm2 and a high emission current density of 1.9 mA/cm2 @ 4.0 V/microm, respectively. 相似文献
8.
This paper describes a thermal evaporation method that generated large-scale novel doorframe-like ITO nanostructures by regularly switching flow rate of the carried gas. Their morphology and microstructures were determined by scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and photoluminescence spectroscopy. The as-synthesized doorframe-like nanostructures are single crystal with diameters ranging from hundreds of nm to about 1 μm. The growth direction of the doorframe-like nanostructures are < 100> and < 011> and the growth process follows a self-catalytic vapor-liquid-solid mechanism. The PL spectrum of the doorframe-like nanostructures shows two emission bands around 418 and 505 nm, which is probably resulted from oxygen vacancies, oxygen-indium vacancy pairs and impurity level, respectively. 相似文献
9.
We describe a new method to grow multi-walled carbon nanotube (MWCNT) arrays, which enable very high and stable macroscopic emission current density of 3.55?A?cm(-2) along with a scalable total emission current of more than 710?mA. A sandwich-growth technology was employed to synthesize vertically well-aligned MWCNT arrays in large areas and patterned uniformly by using microwave plasma chemical vapour deposition. A thick nickel layer was inserted between the silicon substrate and catalyst layer to achieve good adhesion between the MWCNTs and the substrate. Scanning electron microscope and transmission electron microscope investigations showed that well-structured, vertically aligned and uniform MWCNTs with perfect crystal lattices had been grown on lithographically predetermined sites. The root ends of MWCNTs adhered firmly to the nickel layer, establishing high electrical and thermal conductance of the MWCNTs to the substrate. This feature largely explains the large and stable emission current density of the MWCNT arrays. 相似文献
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Qian F Brewster M Lim SK Ling Y Greene C Laboutin O Johnson JW Gradečak S Cao Y Li Y 《Nano letters》2012,12(6):3344-3350
We report the controlled synthesis of AlN/GaN multi-quantum well (MQW) radial nanowire heterostructures by metal-organic chemical vapor deposition. The structure consists of a single-crystal GaN nanowire core and an epitaxially grown (AlN/GaN)(m) (m = 3, 13) MQW shell. Optical excitation of individual MQW nanowires yielded strong, blue-shifted photoluminescence in the range 340-360 nm, with respect to the GaN near band-edge emission at 368.8 nm. Cathodoluminescence analysis on the cross-sectional MQW nanowire samples showed that the blue-shifted ultraviolet luminescence originated from the GaN quantum wells, while the defect-associated yellow luminescence was emitted from the GaN core. Computational simulation provided a quantitative analysis of the mini-band energies in the AlN/GaN superlattices and suggested the observed blue-shifted emission corresponds to the interband transitions between the second subbands of GaN, as a result of quantum confinement and strain effect in these AlN/GaN MQW nanowire structures. 相似文献
12.
Lee YD Blank VD Batov DV Buga SG Lee YH Nahm S Ju BK 《Journal of nanoscience and nanotechnology》2007,7(2):570-574
Carbon-nitrogen (CN) nanofibers were synthesized in argon-nitrogen gas mixture at 75 MPa by high isostatic pressure (HIP) apparatus using a graphite resistive heater. The CN nanofibers were grown in random with the diameter of about 200 nm and the length over 5 microm. The structures obtained can be divided bamboo-like, spring-like, and bead necklace-like CN nanofibers. The nitrogen content of up to 8.4% was found in CN nanofibers by EELS analysis. Field emission results showed that the density of field emitters and the field enhancement factors changed by surface treatments and that CN nanofibers contained glass frit. The screen-printed CN nanofiber had a turn-on field of 2 V/microm. 相似文献
13.
B. M. Ataev I. K. Kamilov A. M. Bagamadova V. V. Mamedov S. Sh. Makhmudov A. K. Omaev Sh. O. Shakhshaev 《Technical Physics Letters》2000,26(9):837-838
The first results on the controlled growth of quasibicrystal structures containing interblock boundaries in epitaxial zinc oxide layers on sapphire (α-Al2O3) are reported. The structures with boundaries oriented in a preset direction can be used as a base for submicron microelectronic devices. Using the method of buffer layers, it is possible to obtain highly oriented layers of (11[`2]0)ZnO(11\bar 20)ZnO and (0001)ZnO with clear boundaries between blocks on the same (10[`1]2)Al2 O3(10\bar 12)Al_2 O_3 substrate surface. Data on the features of structure and morphology of these layers are presented. 相似文献
14.
Chen CY Lai KY Lo JW Lin CA Chiu SH Chao YC He JH 《Journal of nanoscience and nanotechnology》2011,11(12):10615-10619
Electronic structures of well-aligned Er-doped ZnO (ZnO:Er) nanorod arrays (NRAs) synthesized by a solution-based hydrothermal process were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray absorption fine structure (XAFS). HRTEM and angular dependent X-ray absorption near-edge structure analysis at O K and Zn L3 edges indicates that the spontaneous polarization is along the [0001] direction. The analysis of Er L3-edge XAFS demonstrates that the local structure around Er in the ZnO:Er NRAs was transformed from O(h) to C(4v), after annealing. 相似文献
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16.
Yuan Huang Fei Liu Qiang Luo Yuan Tian Qiang Zou Chen Li Chengmin Shen Shaozhi Deng Changzhi Gu Ningsheng Xu Hongjun Gao 《Nano Research》2012,5(12):896-902
Large-area patterned boron carbide nanowires (B4C NWs) have been synthesized using chemical vapor deposition (CVD). The average diameter of B4C NWs is about 50 nm, with a mean length of 20 ??m. The B4C NWs have a single-crystal structure and conductivities around 5.1 × 10?2 ???1·cm?1. Field emission measurements of patterned B4C NWs films show that their turn-on electric field is 2.7 V/??m, lower than that of continuous B4C NWs films. A single nanowire also exhibits excellent flexibility under high-strain bending cycles without deformation or failure. All together, this suggests that B4C NWs are a promising candidate for flexible cold cathode materials. 相似文献
17.
Jiang Zhao Jing Zhang Yanjie Su Zhi Yang Liangming Wei Yafei Zhang 《Journal of Materials Science》2012,47(18):6535-6541
The possibility of preparing straight multi-walled carbon nanotubes (MWCNTs) on a large scale is demonstrated using direct current arc discharge with a rotating graphite anode in low pressure air. The process is time-saving, economical, and non-hazardous. It is found that the optimum air pressure for the highest yield of MWCNTs is about 60 Torr. Investigation of the internal organization of the cathode deposit reveals that many columns about 40 μm in diameter are closely packed and mechanically stable. The highest content of MWCNTs is found in the intercolumnar spaces between columns. Emitters made of the cathode deposits that contain a large number of straight nanotubes exhibit outstanding field emission properties. The turn-on electric field decreases from 1.44 to 0.93 V/μm and the field enhancement factor β increases from about 3,190 to 7,830 only after simple burning at 750 °C for 30 min in air. The results indicate that MWCNTs prepared by arc discharge in air are promising for field emission application. 相似文献
18.
Hui Yang XueFu Shang ZhenHua Li ShaoXing Qu ZhiQi Gu YaBo Xu Miao Wang 《Materials Chemistry and Physics》2010
Large-area and homogeneous single-walled carbon nanotube (SWCNT) films have been deposited via arc discharge directly on glass substrate coated with a layer of indium tin oxide film. The characterization, by means of electron microscopy and Raman spectroscopy, shows that the as-grown films are uniformly woven and consist of SWCNT with diameters ranging from 0.82 to 1.15 nm. As a cathode material, the field emission test indicates the films have low turn-on field of ∼1.2 V/μm at 10 μA/cm2 emission current, and high emission intensity causing luminance of about 7000 cd/cm2 with fine uniformity. The best performing sample exhibits a constant degradation of less than 3% per hour at an emission current of around 1 mA. Measuring with the high voltage (2000 V) on the films for 2.0 h increased the field enhancement factor from 4500 to 5400 at the high field region. The results are of significance to the development of field emission display using nanoemitters. 相似文献
19.
Hung-Hsin Chen Wu-Yih Uen Chien-Te Ku Shan-Ming Lan Tsun-Neng Yang Zhen-Yu Li Chin-Chen Chiang 《Journal of Materials Science: Materials in Electronics》2009,20(Z1):407-411
Well-aligned good-quality carbon nanotube (CNT) array was grown on silicon substrate by atmospheric pressure chemical vapor
deposition (APCVD) through SiO2 masking. First, the patterned substrate was pretreated with NH3 and then CNTs were synthesized at 800 °C using Ni as the catalyst, acetylene (C2H2) as the carbon source material and N2 as the carrier gas. Effects of the NH3-pretreatment time, the flow ratio of [C2H2]/[NH3] and the CNT growth time on the qualities of CNT array were analyzed in detail. It was found that good-quality CNTs with
an average length of around 15 μm could be grown by pretreating the Si substrate with NH3 for 10 min and then conducting the CNT growth with a flow ratio of [C2H2]/[NH3] = 30/100. Furthermore, the field emission property of CNT array was investigated using a diode structure. It was found that
the turn-on electric field decreased with increasing CNT length. The turn-on electric field as low as about 2 V/μm with an
emission current density of 10 μA/cm2 was achieved for a CNT-array diode with the tube length near 18 μm. For the same device, the emission current density could
be elevated to 10 mA/cm2 with the applied voltage of 3.26 V/μm. 相似文献