共查询到20条相似文献,搜索用时 15 毫秒
1.
Dattatray J. Late Vindhyesh R. Singh Sucharita Sinha Mahendra A. More K. Dasgupta Dilip S. Joag 《Applied Physics A: Materials Science & Processing》2009,97(4):905-909
Micro/nano structures have been obtained by laser surface treatment on sintered LaB6 pellets employing a picosecond pulsed Nd:YAG laser at a pressure of ∼1×10−3 mbar. The X-ray diffraction pattern of the laser treated pellet shows a set of well defined diffraction peaks, indexed to
the cubic phase of LaB6 only. The scanning electron microscope studies reveal formation of micro and nano structures upon laser treatment and the
resultant surface morphology is found to be strongly influenced by the laser fluence. Field electron emission studies made
on the LaB6 pellet, treated with optimized laser fluence, have been performed in a planar diode configuration under ultra high vacuum
conditions. The threshold field required to draw an emission current density of ∼10 μA/cm2 has been found to be ∼2.3 V/μm and a current density of ∼530 μA/cm2 has been drawn at an applied field of 5.2 V/μm. The Fowler-Nordheim plot is found to be linear in accordance with the quantum
mechanical tunneling phenomenon, confirming the metallic nature of the emitter. The emission current at the pre-set value
∼10 μA shows very good stability over a period of more than 3 hours. The present results emphasize the effectiveness of a
picosecond laser treatment towards fabrication of a nano metric LaB6 emitter for high current density applications. 相似文献
2.
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
3.
Field emission in diamond and graphite-like polycrystalline films is investigated experimentally. It is shown that the emission
efficiency increases as the nondiamond carbon phase increases; for graphite-like films the threshold electric field is less
than 1.5 V/μm, and at 4 V/μm the emission current reaches 1 mA/cm2, while the density of emission centers exceeds 106 cm−2. A general mechanism explaining the phenomenon of electron field emission from materials containing graphite-like carbon
is proposed.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 56–60 (10 July 1998) 相似文献
4.
Single-crystalline zinc oxide (ZnO) nanorods with cuboid morphology have been prepared on the zinc-filled porous silicon substrate using a vapor phase transport method. Field-emission measurements showed that the turn-on field and threshold field of the cuboid ZnO nanorods film were about 3.2 and 8.2 V/μm respectively. From the emitter surface, a homogeneous emission image was observed with emission site density (ESD) of ∼104 cm−2. The better emission uniformity and the high ESD may be attributed to a large number of ZnO nanocrystallites as emitter on the surface of the nanorod end contributing to emission. 相似文献
5.
The field emission of electrons from a single fine carbon fiber with a nanostructured emitting surface is studied experimentally.
It is found that the fiber can serve as an effective field emitter of electrons at voltages of ∼102–103 under the conditions of technical vacuum and the emission current density may reach ∼102 A/cm2. At a certain threshold voltage, the fiber starts executing flexural mechanical vibrations. The onset of mechanical vibrations
is accompanied by a change in the field emission conditions. Namely, in the absence of vibrations, the mode of steady current
extraction is observed. When mechanical vibrations set in, the field emission switches to the mode of current periodic oscillations
with a constant component. 相似文献
6.
采用丝网印刷法制备了一种大面积的碳纳米管阴极,表征了阴极表面碳纳米管的形貌及分布.研究了该阴极在不同脉冲条件下的高压脉冲发射特性,分析了发射时阴极面等离子体产生和发射点的分布.研究表明:碳纳米管阴极的脉冲发射机制为爆炸电子发射,在平均场强为16.7V/μm的单脉冲电场下,阴极的最高发射电流密度为99 A/cm2.在平均场强为15.4 V/μm的双脉冲电场下,阴极的最高发射电流密度为267 A/cm2.碳纳米管阴极可以作为强流电子束源在高能微波器件中得到应用.
关键词:
强流脉冲电子束
碳纳米管
阴极
丝网印刷 相似文献
7.
通过在碳纳米管(CNTs)表面沉积钛薄膜并经过高温真空退火处理,在CNTs表面形成了低功函数的钛碳化物.研究了钛碳化物改性CNTs的场发射性能,并利用X射线光电子能谱(XPS)对改性碳管进行了结构表征.实验结果表明,高温真空退火可使沉积在CNTs表面的钛原子与碳原子发生化学反应生成钛碳化物;经钛碳化物改性处理的CNTs的场发射性能明显改善,开启电场由改性前的121降低到104V/μm,当电场强度为234V/μm时,场发射电流密度由改性前的23增大到改性后的13.5mA/cm2,同时,CNTs的表面抗离子轰击能力增强,发射稳定性改善.对钛碳化物改性增强CNTs薄膜场发射性能的机理进行了分析.
关键词:
碳纳米管
钛碳化物
场发射
结构表征 相似文献
8.
D. I. Vaisburd S. I. Tverdokhlebov T. A. Tukhfatullin 《Russian Physics Journal》1997,40(11):1064-1082
A dense pulsed electron beam and nanosecond pulse length has been used to inject negative electric charge into various dielectric
materials (single crystals, glasses, composites, plastics) for initiation of electron field emission from the dielectric into
a vacuum. It has been shown that upon reaching a critical electric field in the bulk and at the dielectric surface there is
intense critical electron emission. The local current density from the emission centers reaches a record value (for dielectrics)
of the order of 106 A/cm2. The emission occurs in the form of a single gigantic pulse. The measured amplitude of the emission current averaged over
the emitting surface is the same order of magnitude as the injected electron current: 10–1000 A. the emission current pulse
lages behind the current pulse of the primary electron beam injected into the sample. The delay time is in the range 1–20
nsec and decreases with increasing current density of the injected beam. Direct experimental evidence is found for intense
generation of carriers (band or quasifree electrons) in the near-surface layer of the dielectric in a strong electric field
due to the Frenkel-Poole effect and collisional ionization of traps, usually various donor levels. This process greatly strengthens
the field emission from the dielectric. It has been shown experimentally that the emission is nonuniform and is accompanied
by “point bursts” at the surface of the dielectric and ionized plasma spikes in the vacuum interval. These spikes are the
main reason that the transition of the field emission into “bursts” is critical, similar to the current which has been previously
observed in metals and semiconductors. However there are a number of substantial differences. For example the critical field
emission current density needed for the transition into “bursts” is three orders of magnitude less than for metals. If we
provide sufficient electron current at the surface or from the bulk of the dielectric to the emission centers, then the critical
emission is always accompanied by a vacuum discharge between the surface of the dielectric and a metallic collector. A detailed
computer model of the processes in the dielectric during injection of a high-density electron beam has been developed which
allows one to understand the complex physical pattern of the phenomenon.
Tomsk Polytechnic University. Institute of High-Current Electronics, Siberian Section, Russian Academy of Sciences. Translated
from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 45–67, November, 1997. 相似文献
9.
Jing Xiao Yue Wu Wei Zhang Xin Bai Ligang Yu Shiqi Li Gengmin Zhang 《Applied Surface Science》2008,254(17):5426-5430
Zinc oxide nanopencil arrays were synthesized on pyramidal Si(1 0 0) substrates via a simple thermal evaporation method. Their field emission properties have been investigated: the turn-on electric field (at the current density of 10 μA/cm2) was about 3.8 V/μm, and the threshold electric field (at the current density of 1 mA/cm2) was 5.8 V/μm. Compared with similar structures grown on flat Si substrates, which were made as references, the pyramidal Si-based ZnO nanopencil arrays appeared to be superior in field emission performance, thus the importance of the non-flat substrates has been accentuated. The pyramidal Si substrates could not only suppress the field screening effect but also improve the field enhancement effect during the field emission process. These findings indicated that using non-flat substrates is an efficient strategy to improve the field emission properties. 相似文献
10.
Graham Sanborn Stephan Turano Peter Collins W. Jud Ready 《Applied Physics A: Materials Science & Processing》2013,110(1):99-104
The field electron emission of carbon nanotubes has been heavily studied over the past two decades for various applications, such as in display technologies, microwave amplifiers, and spacecraft propulsion. However, a commercializable lightweight and internally gated electron source has yet to be realized. This work presents the fabrication and testing of a novel internally gated carbon nanotube field electron emitter. Several specific methods are used to prevent electrical shorting of the gate layer, a common failure for internally gated devices. A unique design is explored where the etch pits extend into the silicon substrate and isotropic etching is used to create a lateral buffer zone between the gate and carbon nanotubes. Carbon nanotubes are self-aligned to and within 10 microns from the gate, which creates large electric fields at low potential inputs. Initial tests confirm high field emission performance with an anode current density (based on total area of the device) of 293 μA?cm?2 and a gate current density of 1.68 mA?cm?2 at 250 V. 相似文献
11.
Jun Xu Jiang Zhou Yao Yao Zhanhong Cen Fenqi Song Ling Xu Jianguo Wan Kunji Chen 《Solid State Communications》2008,145(9-10):443-446
Dense Si nano-dots with a surface area density of >1010 cm?2 were fabricated by excimer laser induced crystallization of 15 nm-thick amorphous Si thin films. The enhanced electron field emission characteristics were found from laser irradiated samples. The threshold electric field is as low as 9.8V/μm and the field enhancement factor can reach as large as 719, which is compatible with the other good cold cathode materials. The improvements in field emission behavior can be associated with the change in the surface morphology after laser irradiation as well as the enhanced internal electric field due to the formation of Si nano-dots within the films. 相似文献
12.
S. A. Masalov K. V. Kalinina V. P. Evtikhiev S. V. Ivanov 《Physics of the Solid State》2012,54(6):1126-1130
The field emission injection of low-energy electrons (E e ?? 10 eV) into the ZnSe/CdSe/ZnSe heterostructure has been considered. The probe of the ultra-high-vacuum tunneling microscope has been used as a field emitter. It has been shown that the energy of injected electrons is sufficient for impact ionization in ZnSe. The impact ionization creates a high concentration of nonequilibrium carriers in the near-surface ZnSe layer. The transport of nonequilibrium carriers in the heterostructure under study has been simulated. The electric field of the near-surface space charge and surface recombination have been taken into account. The calculation has demonstrated that filling the active region of CdSe with nonequilibrium carriers is highly efficient. 相似文献
13.
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
14.
利用低压化学气相沉积方法在以Au作催化剂的Si衬底上生长了InN纳米线. 扫描电子显微镜分析表明,这些纳米线的直径在60—100 nm的范围内, 而其长度大于1 μm.高分辨透射电子显微镜图像表明,合成的纳米线中含有六方相和立方相的InN晶体.这些InN纳米线具有良好的场发射特性和稳定的场发射电流,其开启场为10.02 V/μm(电流密度为10 μA/cm2),在24 V/μm 的电场下,其电流密度达到5.5 mA/cm2.此外,对InN纳米线的场发射机理也进行了讨论.
关键词:
InN纳米线
场电子发射
非线性Fower-Nordheim曲线 相似文献
15.
R. B. Rakhi X. Lim X. Gao Y. Wang A. T. S. Wee K. Sethupathi S. Ramaprabhu C. H. Sow 《Applied Physics A: Materials Science & Processing》2010,98(1):195-202
The present work describes the field emission characteristics of nanoscale magnetic nanomaterial encapsulated multi-walled
carbon nanotubes (MWNTs) fabricated over flexible graphitized carbon cloth. Ni/MWNTs, NiFe/MWNTs and NiFeCo/MWNTs have been
synthesized by catalytic chemical vapor decomposition of methane over Mischmetal (Mm)-based AB3 (MmNi3, MmFe1.5Ni1.5 and MmFeCoNi) alloy hydride catalysts. Metal-encapsulated MWNTs exhibited superior field emission performance than pure MWNT-based
field emitters over the same substrate. The results indicate that a Ni-filled MWNT field emitter is a promising material for
practical field emission application with a lowest turn-on field of 0.6 V/μm and a high emission current density of 0.3 mA/cm2 at 0.9 V/μm. 相似文献
16.
Field-electron emission from polyimide-ablated films 总被引:1,自引:0,他引:1
H. Ma L. Zhang N. Yao Z. Bi B. Zhang H. Hu 《Applied Physics A: Materials Science & Processing》2000,71(3):281-284
Polyimide-ablated film was deposited by using pulsed laser ablation of a polyimide target, and field-electron emission from
the film was observed for the first time. The turn-on field of the polyimide-ablated film is 12 V/μm. The current density
is 0.725 mA/cm2, and the emission sites density is on the order of 106/cm2 at the applied field of 24 V/μm. The field-electron emission measurements indicate that this kind of film could be a new
cold cathode material. It is suggested that the graphite-like clusters contained in the film play an important role in the
field-electron emission.
Received: 2 February 2000 / Accepted: 13 March 2000 / Published online: 9 August 2000 相似文献
17.
V. E. Ptitsin 《Technical Physics》2007,52(4):504-509
The field emissivity of ZrO2/W(100) nanoheterostructures made by applying a thin (≈10 nm) ZrO2 layer on the surface of a needle-like W(100) microcrystal is studied. At a nanoheterostructure temperature of ≈2000 K, electron emission is found to start at a low extracting (Laplace) field (below 50 V/μm). Under the conditions of steady electron emission, the emission current density from the surface of the heterostructure may reach anomalously high values (~108 A/cm2). A phenomenological model of anomalous thermal field emission of electrons from the surface of the conductor (metal)-thin insulator heterostructure is suggested. 相似文献
18.
A reduced surface electric field in AlGaN/GaN high electron mobility transistor (HEMT) is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas (2-DEG) channel as an electric field shaping layer. The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions. Compared with the HEMTs with conventional source-connected field plate and double field plate, the HEMT with Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge. By optimizing both the length of Mg-doped layer, Lm, and the doping concentration, a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure, respectively. In a device with VGS=-5 V, Lm=1.5 μm, a peak Mg doping concentration of 8× 1017 cm-3 and a drift region length of 10 μm, the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty. 相似文献
19.
Field emission from single-walled carbon nanotubes (SWNTs) aligned on a patterned gold surface is reported. The SWNT emitters
were prepared at room temperature by a self-assembly monolayer technique. SWNTs were cut into sub-micron lengths by sonication
in an acidic solution. Cut SWNTs were attached to the gold surface by the reaction between the thiol groups and the gold surface.
The field-emission measurements showed that the turn-on field was 4.8 V/μm at an emission current density of 10 μA/cm2. The current density was 0.5 mA/cm2 at 6.6 V/μm. This approach provides a novel route for fabricating CNT-based field-emission displays.
Received: 3 May 2002 / Accepted: 6 May 2002 / Published online: 4 December 2002
RID="*"
ID="*"Corresponding author. Fax: +82-54/279-8298, E-mail: ce20047@postech.ac.kr 相似文献
20.
Dattatray J. Late Ranjit V. Kashid Chandra Sekhar?Rout Mahendra A. More Dilip S. Joag 《Applied Physics A: Materials Science & Processing》2010,98(4):751-756
Field emission studies of WO2.72 nanowires synthesized by a solvothermal method have been performed in the planar diode configuration under ultra high vacuum
conditions. Fowler–Nordheim plots obtained from the current-voltage characteristics follow the quantum mechanical tunneling
process and a current density of ∼8.3×106 μA/cm2 can be drawn at an applied electric field of 2 V/μm. The field enhancement factor is 33025, while the turn-on field is only
1.4 V/μm. The emission current-time plot recorded at the pre-set value of emission current of 1 μA over a period of more than
3 h exhibits an initial increase and a subsequent stabilization of the emission current. The results reveal that the WO2.72 nanowire emitters synthesized by the solvothermal method are promising cathode materials for practical applications. 相似文献