共查询到20条相似文献,搜索用时 31 毫秒
1.
Chen Hong-sheng Qi Jun-jie Zhang Yue Liao Qing-liang Huang Yun-hua 《Frontiers of Physics in China》2007,2(2):195-198
The direct growth of a tetrapod-like ZnO nanostructure has been accomplished by using a thermal oxidation method without any
catalysts. Studies on the field emission properties of the ordered ZnO nanotetrapods films found that the shape of the ZnO
nanotetrapods has considerable effect on their field emission properties, especially the turn-on field and the emission current
density. Compared with the rod-like legs ZnO nanotetrapods, the nanotetrapods with acicular legs have a lower turn-on field
of 2.7 V/μm at a current density of 10 μA/cm2, a high field enhancement factor of 1830, and an available stability. More importantly, the emission current density reached
1 mA/cm2 at a field of 4.8 V/μm without showing saturation. The results could be valuable for using the ZnO nanostructure as a cold-cathode
field-emission material.
相似文献
2.
W. Bai K. Yu Q. Zhang Y. Huang Q. Wang Z. Zhu N. Dai Y. Sun 《Applied Physics A: Materials Science & Processing》2007,87(4):755-759
ZnO nanorods with 30 nm-diameter ultra-thin pinheads and ultra-thin nanobelts were successfully synthesized using a thiourea
solution to etch nanorods and nancombs, which were obtained by a conventional thermal evaporation method. The materials obtained
were investigated by field emission scanning electron microscopy and energy-dispersive X-ray fluorescence. The data shows
that hydrogen ions play an important role in synthesizing ZnO nanorods with ultra-thin pinheads and ultra-thin nanobelts.
Field emission plots indicated that the turn-on field was reduced from 2.10 V/μm to 1.55 V/μm after thiourea solution treatment
at a current density of 0.1 μA/cm2. Room-temperature photoluminescence spectra from ZnO nanostructures showed the PL spectrum peaks shifted towards short wavelengths
with a large enhancement of UV bands compared with those of ZnO nanorods and nanocombs.
PACS 75.55.Gs; 61.46.-w; 81.40.Wx; 78.55.-m; 78.60.Fi 相似文献
3.
Hexagonal GaN prismatic sub-micro rods and cone nanowires have been synthesized in a large scale by a novel and controllable
space-confined growth method. The as-synthesized GaN products are highly crystalline with a wurtzite structure. The prismatic
rods have lengths of 15∼20 μm and diameters of 400∼500 nm enclosed by hexagonal smooth side surfaces and a pyramidal end.
And the cone nanowires have average diameters of 150∼200 nm and lengths up to several tens of μm with a cone tip. The photoluminescence
(PL) studies reveal prominent band-gap UV emission properties of GaN products and narrow FWHM, indicating the excellent luminescent
performance and high crystal quality. For field emission characteristic of GaN nanowires, the turn-on field is about 9.5 V/μm
and the current density reaches 1.0 mA/cm2 at an electric field of 18 V/ μm. The contrast experiments indicate a novel growth control can be achieved by using a graphite
tube as reaction vessel. The sealed graphite tube combined with metallic initiator is greatly responsible for large-scale
and uniform preparation of GaN prismatic rods and cone nanowires. Highly symmetric GaN hexagonal micropyramids are grown on
a bare Si substrate. The growth mechanism and the control function of the graphite tube are demonstrated. These low-dimensional
structures not only enrich semiconducting GaN family, but also are good building blocks for optoelectronic devices.
PACS 81.10.Bk; 81.07.-b; 81.05.Ea 相似文献
4.
ZnS and ZnO films were prepared on porous silicon (PS) substrates with the same porosity by pulsed laser deposition (PLD), and the structural, optical and electrical properties of ZnS and ZnO films on PS were investigated at room temperature by X-ray diffraction (XRD), scanning electron microscope (SEM), optical absorption measurement, photoluminescence (PL) and I–V characteristic studies. The prepared ZnS was obtained in the cubic phase along β-ZnS (1 1 1) orientation which showed a perfect match with the earlier report while ZnO films were obtained in c-axis orientation. There appeared some cracks in the surface of ZnS and ZnO films due to the roughness of PS substrates. Luminescence studies of ZnS/PS and ZnO/PS composites indicated room temperature emission in a broad, intense, visible photoluminescence band, which cover the blue emission to red emission, exhibiting intensively white light emission. Based on the I–V characteristic, ZnS/PS heterojunction exhibited the rectifying junction behavior, while the I–V characteristic of ZnO/PS heterostructure was different from that of the common diode, whose reverse current was not saturated. 相似文献
5.
Dapeng Wu Yi Jiang Yafei Yuan Junshu Wu Kai Jiang 《Journal of nanoparticle research》2011,13(7):2875-2886
ZnO–ZnS heterostructures were fabricated via using ZnO rods as template in different Na2S aqueous solutions. These heterostructures are 5–6 μm in length and formed by coating ZnO rod with a layer of porous ZnS
shell comprising primary crystals about 10 nm in diameter. Subsequently, intact ZnS polycrystalline tubes were obtained by
removing the ZnO cores with 25% (wt) ammonia. The as-prepared products were characterized by scanning electronic microscopy
(SEM), transmission electronic microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), Fourier
transform infrared (FT-IR), and electrochemical impedance spectroscopy (EIS). It was found that the electron transfer between
ZnS shell and ZnO core strongly affect the photoluminescence and photocatalytic performances of these heterostructures. The
rapid transfer of photo-induced electrons from the ZnS shell to the ZnO core leads to enhanced ultraviolet emission. However,
if this correlation was destroyed, then the corresponding heterostructure exhibits improved photocatalytic efficiency due
to the reduced volume recombination of the charge carries and the multiple reflection effect. Finally, a model based on band-gap
alignment was proposed to elucidate the underlying mechanism of the enhanced UV emission and photocatalytic activity of these
unique heterostructures. 相似文献
6.
P. Zhang H. Qi X. Zhang Q. Zhao Y. Tian D. Yu 《Applied Physics A: Materials Science & Processing》2006,84(1-2):165-169
Novel lotiform ZnO nanostructures were synthesized on silicon substrate via simple thermal evaporation. The average diameter of the ZnO nanostructures is ∼1.5 μm. The lotiform-like ZnO structures were formed by nanorods arrays with the average diameter of 70 nm. The as-grown lotiform ZnO nanostructures have excellent field-emission properties such as the low turn-on field of 3.4 V/μm, and very high emission current density of 12.4 mA/cm2 at the field of 9.6 V/μm. These features make the lotiform-like ZnO nanostructures competitive candidates for field-emission-based displays. PACS 61.46.-w; 61.82.Rx; 78.67.-n; 73.63.Bd; 74.78.Na 相似文献
7.
R. Maity S. Das M.K. Mitra K.K. Chattopadhyay 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):605-612
Zinc oxide (ZnO) nano/microfibrous thin films were successfully synthesized by a catalyst free solution route on glass and Si substrates. X-ray diffraction study revealed the formation of ZnO nanofibers of hexagonal crystalline structure. The texture coefficient of different planes varied with annealing temperature and that of the (0 0 2) plane was the highest for films annealed at temperature 873 K. Scanning electron micrograph showed the well formation of ZnO nano/microfibers with an average diameter 500 nm and having an average aspect ratio 150. UV–Vis–NIR spectroscopic study for the films deposited on glass substrates showed the high transmittance in the visible and near-infrared region. It was also observed that the band gap energy decreased as the films were annealed at higher temperature. The band gap energies of nanostructured ZnO thin films were determined to be in the range 3.03–3.61 eV. The photoluminescence study showed an UV emission peak at 397 nm, a visible blue–green emission peak at 468 nm and a green emission peak at 495 nm. Field emission properties of nanofiber ZnO thin film showed considerably low turn-on field around 1.4 V/μm. The emission current was as high as 70 μA at the field of 3.6 V/μm. 相似文献
8.
Q.X. Zhao P. Klason M. Willander 《Applied Physics A: Materials Science & Processing》2007,87(1):27-30
Zinc oxide nanorods have been grown by vapor–liquid–solid (VLS) catalytic growth. The optical properties and structures properties
of the grown ZnO nanostructures have been studied by photoluminescence, high resolution X-ray diffraction and scanning electron
microscopy. The results show that the formation of ZnO nanostructures is strongly influenced by the growth conditions and
used substrates. It was found that oriented ZnO nanorods are grown more easily on a substrate with a similar crystalline structure
as ZnO. By optimizing growth conditions, oriented-ZnO nanorods grown on Si(001) substrate with a diameter of around 300 nm
and lengths of 20 to 35 μm have been achieved, and they show excellent optical properties. Laser action has been observed
at room temperature by using optical pumping.
PACS 81.05.Dz; 81.10.Bk; 81.16.Hc 相似文献
9.
Cuicui Wang Ke Yu Lijun Li Qiong Li Ziqiang Zhu 《Applied Physics A: Materials Science & Processing》2008,90(4):739-743
Two kinds of ZnO nanotubes, including taper-like and flat-roofed tubes, have been successfully fabricated using a simple aqueous
solution route by changing the experimental conditions. All the obtained nanotubes have a uniform size of 500 nm in diameter,
10–50 nm in wall thickness, and 2–5 μm in length. The growth mechanism of two kinds of ZnO nanotubes was investigated. Field
emission measurements showed that tapering nanotubes have the good field emission performance with a low turn-on field of
∼ 2.1 V μm-1 and a low threshold field of ∼ 3.8 V μm-1, which suggests the possible applications of the ZnO tubular structures in field emission microelectronic devices.
PACS 73.61.Ga; 73.63. Fg; 85.45.Db 相似文献
10.
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
11.
Highly ordered and stepped ZnO comb-like structures were fabricated using conventional thermal evaporation method. Zn powder covered by a layer of a mixture of ZnO and graphite was employed as the Zn source. The obtained ZnO comb-like structures are several tens of micrometers and some of them are even up to 100 μm. Both the widths of the belts and the lengths of the branches gradually decrease along the growth direction of ZnO comb-like structures. Under the most suitable condition, ZnO nanorods branches have uniform diameters and are evenly distributed on the belt-like stem. Possible growth process of ZnO comb-like structures was discussed. The effect of growth temperature on the morphology of the obtained products was also investigated. Room-temperature photoluminescence spectra from the ZnO comb-like structures and the nanorods film reveal weak UV emission and strong green emission. 相似文献
12.
A. Klini A. Mourka V. Dinca C. Fotakis F. Claeyssens 《Applied Physics A: Materials Science & Processing》2007,87(1):17-22
We report a method for micropatterning (25–900 μm2 pixel size) of ZnO nanorods onto a silicon substrate via a low-temperature (overall under 100 °C) two-step process, involving
a laser-based direct-write technique (laser-induced forward transfer) and sequential chemical growth. The rods produced via
this route are aligned in the [0001] crystal direction. Photoluminescence shows, next to the band-gap emission, strong green-yellow
emission centred at ∼570 nm. Additionally, the rod arrays show excellent field-emission properties with a threshold field
for emission of 5 V/μm.
PACS 61.82.Rx; 81.10.Dn; 81.16.Mk 相似文献
13.
Enhanced optical and field emission properties of CTAB-assisted hydrothermal grown ZnO nanorods 总被引:1,自引:0,他引:1
We have developed a simple N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB)-assisted hydrothermal route for the production of ZnO one-dimensional (1D) nanostructures on zinc foil at reaction temperature of 160 °C. With the increase of CTAB concentration, the one-dimensional structures change from microrod to a mixture of nano- and microrod and finally to nanorods. X-ray diffraction studies confirmed the proper phase formation of the grown nanostructures. The room temperature photoluminescence spectra showed that ZnO nanostructures prepared with increased CTAB concentration exhibited enhanced band edge UV emission and also blue shift of the emission peak. All the samples show no defect related green emission. Field emission property of the 1D structures has been investigated in detail. By tuning the CTAB concentration, the field emission property was optimized. The nanorods synthesized with high CTAB showed turn-on and threshold fields of 3.2 and 5 V/μm, respectively, which are comparable to the values for vapour phase synthesized high field emitting ZnO nanostructures. 相似文献
14.
Fuxue Wang Yao Yao Dawei Yan Zhaomin Zhu Xiaofeng Gu 《Applied Physics A: Materials Science & Processing》2014,116(3):1173-1179
The pencil-like and shuttle-like ZnO microrods have been fabricated on Si (100) substrates by chemical vapor deposition. Structure characterization results show that the microrods are perfect single crystals with the wurtzite structure along the [0001] growth direction and have diameters ranging from 100 nm to 2 μm and lengths up to 10 μm. Room-temperature photoluminescence measurements of ZnO microstructures exhibit an intensive ultraviolet peak at 390 nm and a broad peak centered at about 526 nm, which can be attributed to the free exciton emission and the deep level emission, respectively. Cathodoluminescence measurements show the same ultraviolet and green emissions as seen in the photoluminescence results. A possible growth mechanism of ZnO microrods is finally proposed. 相似文献
15.
X. Lu Q. Yang C. Xiao A. Hirose 《Applied Physics A: Materials Science & Processing》2006,82(2):293-296
Diamond nanocone, graphitic nanocone, and mixed diamond and graphitic nanocone films have been synthesized through plasma
enhanced hot filament chemical vapor deposition (HFCVD). The field emission properties of these films have been experimentally
investigated. The studies have revealed that all three kinds of nanocone films have excellent field electron emission (FEE)
properties including low turn-on electric field and large emission current at low electric field. Compared with the diamond
nanocone films (emission current of 86 μA at 26 V/μm with the turn-on field of 10 V/μm), the graphitic nanocone films exhibit
higher FEE current of 1.8×102 μA at 13 V/μm and a lower turn-on filed of 4 V/μm. The mixed diamond and graphitic nanocone films have been found to posses
FEE properties similar to graphitic nanocone films (emission current of 1.7×102 μA at 20 V/μm with the turn-on field of 5 V/μm), but have much better FEE stability than the graphitic nanocone films.
PACS 81.07.Bc; 81.05.Uw; 79.70.+q 相似文献
16.
F. Liang C. W. Zou W. Xie S. W. Xue 《Applied Physics A: Materials Science & Processing》2014,116(1):243-249
We have developed a straightforward and simple strategy for large-scale growth of well-aligned ZnO nanoneedles via a thermal evaporation method. XRD and SAED patterns of nanoneedles can be indexed to hexagonal ZnO with wurtzite structure. Room temperature photoluminescence analysis showed a strong ultra violet emission at 365 nm and a broad deep level visible emission at 472 nm. The growth mechanism of the nanoneedles has been investigated by SEM and the lower pressure of both evaporated zinc and oxygen flux would favor the nucleation of the finer nanowires from those previously formed high coverage spots. The field emission current density of ZnO nanoneedles sharply reached ~0.048 mA/cm2 at a field of 3.1 V/m. 相似文献
17.
Woo Hyun Nam Young Soo Lim Won-Seon Seo Hyung Koun Cho Jeong Yong Lee 《Journal of nanoparticle research》2011,13(11):5825-5831
Nanostructured ZnO–ZnS core-shell powders were synthesized through a solution method using a thioacetamide (TAA) solution
in deionized water. ZnO powder and TAA solution were employed to supply zinc and sulfur ions to form the ZnO–ZnS core-shell
structures. The structure of the ZnS shell was strongly affected by the mole concentration of the TAA, and the structural
properties were characterized by X-ray diffraction and high-resolution transmission electron microscopy. The optical properties
of the nanostructured powders were also compared with those of pure ZnO powder. The ultraviolet (UV) emission was greatly
enhanced compared to when pure ZnO powder was used in the nanostructured powder synthesized using the 0.5 M TAA solution,
while the UV emission of that with the 0.05 M TAA solution was reduced. The green emission of the nanostructured powders was
reduced compared to when the pure ZnO powder was used. The mechanism of the structural changes in the core-shell structures
is proposed here and its effect on the luminescent properties is discussed. 相似文献
18.
S.K. Mishra R.K. Srivastava S.G. Prakash R.S. Yadav A.C. Panday 《Opto-Electronics Review》2010,18(4):467-473
In the present paper, ZnO nanoparticles (NPs) with particle size of 20–50 nm have been synthesized by hydrothermal method.
UV-visible absorption spectra of ZnO nanoparticles show absorption edge at 372 nm, which is blue-shifted as compared to bulk
ZnO. Photoluminescence (PL) and photoconductive device characteristics, including field response, light intensity response,
rise and decay time response, and spectral response have been studied systematically. The photoluminescence spectra of these
ZnO nanoparticles exhibited different emission peaks at 396 nm, 416 nm, 445 nm, 481 nm, and 524 nm. The photoconductivity
spectra of ZnO nanoparticles are studied in the UV-visible spectral region (366–691 nm). In spectral response curve of ZnO
NPs, the wavelength dependence of the photocurrent is very close to the absorption and photoluminescence spectra. The photo
generated current, Ipc = (Itotal - Idark) and dark current Idc varies according to the power law with the applied field IpcαVr and with the intensity of illumination IpcαIL
r, due to the defect related mechanism including both recombination centers and traps. The ZnO NPs is found to have deep trap
of 0.96 eV, very close to green band emission. The photo and dark conductivities of ZnO NPs have been measured using thick
film of powder without any binder. 相似文献
19.
L.L. Xu X.L. Wu X. Xiong J. Zhu H.T. Chen G.S. Huang P.K. Chu 《Applied Physics A: Materials Science & Processing》2008,91(2):247-250
Self-assembled roselike ZnO nanostructures were synthesized via thermal evaporation of zinc powders without catalytic assistance
at the relatively low temperature of 550 °C. The roselike structures consist of a large number of ZnO nanorods that uniformly
arrange into hexagonal multilayers. The spontaneous nanoindentation effects under geometric constraints can be used to explain
the structures. The cathodoluminescence spectra show a wide visible emission band related to Zn interstitials and oxygen vacancies.
Field emission measurements demonstrate that the roselike ZnO nanostructures possess good electron emission characteristics
with a turn-on field of 4.3 V/μm.
PACS 68.70.+w; 78.55.Cr; 81.05.Cy 相似文献
20.
Enhanced field emission from pulsed laser deposited nanocrystalline ZnO thin films on Re and W 总被引:1,自引:0,他引:1
Dattatray J. Late Pankaj Misra B. N. Singh Lalit M. Kukreja Dilip S. Joag Mahendra A. More 《Applied Physics A: Materials Science & Processing》2009,95(2):613-620
Nanocrystalline ZnO thin films have been deposited on rhenium and tungsten pointed and flat substrates by pulsed laser deposition
method. An emission current of 1 nA with an onset voltage of 120 V was observed repeatedly and maximum current density ∼1.3 A/cm2 and 9.3 mA/cm2 has been drawn from ZnO/Re and ZnO/W pointed emitters at an applied voltage of 12.8 and 14 kV, respectively. In case of planar
emitters (ZnO deposited on flat substrates), the onset field required to draw 1 nA emission current is observed to be 0.87
and 1.2 V/μm for ZnO/Re and ZnO/W planar emitters, respectively. The Fowler–Nordheim plots of both the emitters show nonlinear
behaviour, typical for a semiconducting field emitter. The field enhancement factor β is estimated to be ∼2.15×105 cm−1 and 2.16×105 cm−1 for pointed and 3.2×104 and 1.74×104 for planar ZnO/Re and ZnO/W emitters, respectively. The high value of β factor suggests that the emission is from the nanometric features of the emitter surface. The emission current–time plots
exhibit good stability of emission current over a period of more than three hours. The post field emission surface morphology
studies show no significant deterioration of the emitter surface indicating that the ZnO thin film has a very strong adherence
to both the substrates and exhibits a remarkable structural stability against high-field-induced mechanical stresses and ion
bombardment. The results reveal that PLD offers unprecedented advantages in fabricating the ZnO field emitters for practical
applications in field-emission-based electron sources. 相似文献