共查询到20条相似文献,搜索用时 843 毫秒
1.
Ki Seo Kim Je Hwang Ryu Chang Seok Lee Jin Jang Kyu Chang Park 《Journal of Materials Science: Materials in Electronics》2009,20(Z1):120-124
Carbon nanotubes (CNT) have been highlighted as possible candidates for field-emission emitters and vacuum nanoelectronic
devices. In this article, we studied the effect of acid treatment of CNTs on field emission from carbon nanotube field emitter
arrays (FEAs), grown using the resist-assisted patterning process (RAP). The emission current densities of as grown CNT-FEAs
and those which were later immersed in hydrofluoric acid (HF) for 20 s, were 19 μA/cm2 and 7.0 mA/cm2, respectively, when measured at an anode field of 9.2 V/μm. Hence, the emission current densities after HF treatment are
300 times larger than those of as grown CNT-FEAs. Also, it was observed that a very stable electron emission current was obtained
after stressing the CNTs with an electric field of 9.2 V/μm for 800 min in dc-mode, where the emission current non-uniformity
was 0.13%. The enhancement in electron emission after HF treatment appears to be due to the effect of fluorine bonding. Also,
the electron emission characteristics and structural improvement of CNT-FEAs after HF treatment are discussed. 相似文献
2.
A two-dimensional distribution function in the frequency range 0.03–1 Hz was used to investigate the statistical characteristics
of the fluctuations of the field emission current from single crystals of tungsten and p-type silicon. In order to determine the type of nonlinearity predominating in the low-frequency noise of the emission current,
calculations were made of the two-dimensional distribution function for a Gaussian random process subjected to a given type
of nonlinear transformation and the profiles of the experimental two-dimensional distribution functions were compared with
dependences obtained by numerical methods. It was established that fluctuations of the effective emitting surface of the cathode,
the barrier transmission, the work function, and of the electric field strength near the emitter surface may act as primary
sources of low-frequency noise in the field emission current.
Pis’ma Zh. Tekh. Fiz. 24, 87–93 (November 12, 1998)
Paper presented at the International Conference on Emission Electronics, Tashkent, Republic of Uzbekistan, 4–6 November 1997. 相似文献
3.
Multilayer cathode electrodes consisting of Al2O3 bufferlayer, Cu conductive layer and InSnO3 current limiting layer, used in carbon nanotube (CNT) field emission display, were prepared by direct current magnetron sputtering and wet etching. Compared with conventional monolayer cathode electrodes, the multilayer electrodes possess higher current limiting resistance with lower inherent resistance variation. Profilometer measurement indicates the etched edges of the multilayer electrodes were abrupt and regular. Nano Indenter experiment shows that the multilayer electrodes remained intact after annealing treatment and were resistance to scratch damage at loads up to 12.6 mN. X-ray diffraction analysis reveals that no oxidized copper was formed during the annealing treatment. Atomic force microscope images show that the surface of the multilayer electrodes became smoother after plasma bombardment, and the maximum protrusion height decreased from 48.6 nm to 15.4 nm. With the multilayer cathode electrodes, the field emission properties of CNT film cathodes, such as uniformity, lifetime and stability are improved. 相似文献
4.
A newly developed vacuum sensor using carbon nanotube (CNT) field-emission has been designed. The fabricated device is an ionization gauge with a silk-like CNT yarn cathode, and the vacuum is indicated by the ratio of the ion current to the electron-emission current. The metrological characteristics of the sensor were studied in a dynamic vacuum system. It showed good linearity ranged from 10−4 to 10−1 Pa. Taking advantage of the field-emission cathode, the power consumption is only about 5.5 mW. Moreover, comparing it to the conventional thermionic cathode, the CNT yarn cathode is more miniature and a cold cathode with no obvious thermal outgassing effect. Due to these features, the sensor described here could have potential applications in measuring vacuum inside sealed and miniaturized devices. 相似文献
5.
We study the influence of longitudinal magnetic field on the radiation of low-pressure glow discharges in hydrogen and helium.
We conducted experiments under a pressure in a discharge chamber of 10–20 Pa and a discharge current of 10–20 mA. A 0–1600
G magnetic field influenced only the cathode parts of the discharge, negative glow, and the dark Faraday space. The electron
temperature and density were measured by the two-probe method as a function of magnetic field. We studied the dependence of
the intensity of radiation in the spectral lines and continuous spectrum on magnetic field induction. We discovered that,
under the action of magnetic field, discharge in hydrogen and helium is compressed and its glow volume increases by a factor
of 20–25. In contrast, the radiation intensity in the lines and continuous spectrum increase by a factor of 100–200. We found
a strong discrepancy in the measured intensity of the continuous spectrum into spectral ranges with calculation of electron-ion
recombination. 相似文献
6.
Effects of bonding materials in a screen-printing paste on field emission properties were investigated for carbon nanotube (CNT) cathodes. The CNT cathodes were characterized for their dependence on current density in terms of the sintering behavior of the bonding material. As the diameter of the Ag particles in the bonding material decreased from 1000 nm to 10 nm, the current density of the CNT cathode increased. The sintering temperature of bonding materials was decreased for small silver (Ag) particles in bonding material. The higher current density for a CNT cathode fabricated with smaller Ag particles was primarily due to the lower sheet resistance of the bonding material after heat treatment. 相似文献
7.
X-ray imaging data obtained from cold cathodes using gallium-doped zinc oxide (GZO)-coated CNT emitters are presented. Multi-walled CNTs were directly grown on conical-type (250 μm-diameter) tungsten-tip substrates at 700 °C via inductively coupled plasma-chemical vapor deposition (ICP-CVD). GZO films were deposited on the grown CNTs at room temperature using a pulsed laser deposition (PLD) technique. Field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) were used to monitor the variations in the morphology and microstructure of the CNTs before and after GZO coating. The formation of the GZO layers on the CNTs was confirmed using energy-dispersive X-ray spectroscopy (EDX). The CNT-emitter that was coated with a 10-nm-thick GZO film displayed an excellent performance, such as a maximum emission current of 258 μA (at an applied field of 4 V/μm) and a threshold field of 2.20 V/μm (at an emission current of 1.0 μA). The electric-field emission characteristics of the GZO-coated CNT emitter and of the pristine (i.e., non-coated) CNT emitter were compared, and the images from an X-ray system were obtained by using the GZO-coated CNT emitter as the cold cathode for X-ray generation. 相似文献
8.
M. Messaad A. W. Belarbi M. Abbaoui A. Lefort 《Journal of Engineering Physics and Thermophysics》2007,80(6):1130-1139
Experimental and theoretical studies of the arc-cathode region have been made for several decades, but the task is not yet
complete, despite many efforts and much progress. In this work, a numerical model describing the arc-cathode region is developed.
The arc is treated as a steady-state phenomenon. The model is then applied to a vacuum arc discharge interacting with a Cu
cathode at low current of 4–50 A. The model yields the temperature and electric field strength at the cathode surface, density
of the current of the electrons emitted, total current density, cathode spot radius, different kinds of power densities in
heating and cooling the cathode, and the plasma electron density. The comparison with experimental results shows good agreement.
Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 63–72, November–December, 2007. 相似文献
9.
M. Aidaraliev N. V. Zotova S. A. Karandashev B. A. Matveev M. A. Remennyi N. M. Stus’ G. N. Talalakin 《Technical Physics Letters》1998,24(3):243-245
Graded-index p-n InAsSb/InAsSbP/InAs structures capable of emitting at the maximum of the spectral curve up to 5.4 μm with a half-width of ∼26 meV (∼0.6 μm) without cooling have been fabricated and studied. This is the longest-wavelength radiation obtained at room temperature
in III–V structures grown by liquid-phase epitaxy and the band is the narrowest obtained for semiconductor spontaneous radiation
sources.
Pis’ma Zh. Tekh. Fiz. 24, 88–94 (March 26, 1998) 相似文献
10.
S.?I.?Tanase D.?Pinzaru? V.?Georgescu 《Journal of Superconductivity and Novel Magnetism》2011,24(8):2313-2319
The effect of nitrogen addition on the morphology, magnetic anisotropy, and magnetoresistance properties of Co–Ni–N granular
thin films were investigated. The films were grown by electrodeposition onto aluminum substrates at room temperature. By a
complex process of cationic catalysis occurring at the cathode/electrolyte interface, nitrogen is adsorbed in the Co–Ni film.
Finally, a granular film grows by a tridimensional progressive nucleation mechanism. The nature of the grains and of the interface
between them influences exchange interactions between grains, which play an important role in determining the magnetic anisotropy.
From the magnetic measurements, we found that the magnetic anisotropy constant varied in the range K
eff=(−21.5÷36.6)×104 J⋅m−3 and the coercivity varied between H
c=(13÷67) kA⋅m−1 depending on the sodium nitrate content in the plating bath. The Co–Ni–N granular thin films display large values (∼160%)
of magnetoresistance. These large values of magnetoresistance make such structures attractive for applications as sensitive
magnetic field sensors. 相似文献
11.
Double-walled carbon nanotubes (DWCNTs) with high graphitization have been synthesized by hydrogen arc discharge. The obtained
DWCNTs have a narrow distribution of diameters of both the inner and outer tubes, and more than half of the DWCNTs have inner
diameters in the range 0.6–1.0 nm. Field electron emission from a DWCNT cathode to an anode has been measured, and the emission
current density of DWCNTs reached 1 A/cm2 at an applied field of about 4.3 V/μm. After high-temperature treatment of DWCNTs, long linear carbon chains (C-chains) can
be grown inside the ultra-thin DWCNTs to form a novel C-chain@DWCNT nanostructure, showing that these ultra-thin DWCNTs are
an appropriate nanocontainer for preparing truly one-dimensional nanostructures with one-atom-diameter.
相似文献
12.
Flow-through capacitor (FTC) with carbon nanotube (CNT) electrode was employed to remove NaCl from saltwater solution. According
to the investigation by transmission electron microscopy (TEM) and nitrogen adsorption, the BET specific surface area of CNT
electrodes decreased with increasing nanotube diameter, which had a narrow distribution in each sample. Besides, removal of
NaCl per unit weight of CNT electrode increased linearly with the BET specific surface area of CNT electrodes. As a result,
CNT electrode with the smallest nanotube diameter had the best removal characteristic, with removal efficiency up to 95% and
energy-consumption of 3.0 Wh L−1, and the process of regeneration could be carried out easily in a short time. Comparing removal experiment with charge/discharge
test, it was concluded that FTC based on the same electro-adsorption theory as double layer capacitors. The cyclic voltammograms
of CNT electrode in salt water showed that the current occurred by adsorption and desorption of ions in the range of −0.3–0.9 V,
which directly explained the reason why CNT electrode could be used to remove NaCl. 相似文献
13.
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
14.
Yueli Liu Lei Zhong Zhuoyin Peng Yanbao Song Wen Chen 《Journal of Materials Science》2010,45(14):3791-3796
In this article, the field-emission property of individual CuO nanoneedle was investigated to explore its tip image and real
work function using in situ transmission electron microscopy. The maximum emission current of nanoneedle used in this study
was 1.08 μA, and two different slopes in the corresponding F–N graph existed with work functions of the CuO nanoneedle being
1.12 and 0.58 eV. In comparison with the single CuO nanoneedle, the field enhancement β and parameter s of the CuO nanoneedle’s film arrays were also studied, which showed that the screening effect played a key role in the field-emission
process. 相似文献
15.
S. V. Grigor’ev V. N. Devyatkov N. N. Koval’ A. D. Teresov 《Technical Physics Letters》2010,36(2):158-161
We have experimentally studied the phenomenon of emission enhancement in a gas-filled diode with grid-stabilized plasma cathode
and open (mobile) anode plasma boundary at an accelerating voltage of up to 20 kV. As the working gas pressure is increased
to p ≥ 10−2 Pa and the longitudinal magnetic field is increased to B
z
≥ 20 mT, the current in the accelerating gap exhibits significant growth, sometimes by a factor of two or more. Experimental
data show that the most probable mechanism responsible for this effect is ion-induced secondary electron emission from the
emitting electrode surface bombarded by ions from plasma generated by the electron beam in the drift space. These ions are
accelerated in the space charge layer between the emitting electrode surface and the mobile boundary of the beam-generated
(anode) plasma. 相似文献
16.
Moshe Dayan 《Journal of Superconductivity and Novel Magnetism》2006,19(6):477-484
We reexamine the Nambu–Gorkov perturbation theory of superconductivity. We suggest that any field perturbation theory of superconductivity
should be based on the Bogoliubov–Valatin (BV) quasi-particles. We show that two such different fields (and two additional
analogous fields) may be constructed on the basis of this suggestion. The Nambu field is only one of them. For the field that
is different than Nambu’s, the coherence field, the interaction is given by means of two interaction vertices that are based
on the Pauli matrices τ1 and τ3. Consequently, the Hartree integral for the off-diagonal pairing self-energy may be finite, and in some cases large. We interpret
the results in terms of conventional superconductivity and also discuss briefly the possible implications to HTSC. 相似文献
17.
Yu. V. Korobkin S. P. Gorbunov V. V. Myaekivi V. L. Paperny 《Technical Physics Letters》2010,36(5):447-450
Low-voltage vacuum spark discharge initiated at a storage capacitor voltage of 75–600 V using a metal grid cathode situated
on the front surface of a polarized ferroelectric (FE) electrode has been experimentally studied. The discharge was initiated
when a control voltage pulse with an amplitude of 1 kV and a duration of 100 ns at only negative polarity was applied to the
rear FE surface (irrespective of the direction of its polarization vector). Optical measurements showed that the emitting
surface area on the cathode increases approximately in proportion to the discharge voltage. According to the collector measurements,
the ion plasma flux has slow and fast components, the velocities of which remain almost constant when the discharge current
amplitude varies in a wide interval. 相似文献
18.
This paper aims to statistically estimate the dynamic fatigue strength in brittle materials under a wide range of stress rates.
First, two probabilistic models were derived on the basis of the slow crack growth (SCG) concept in conjunction with two-parameter
Weibull distribution. The first model, Model I, is a conventional probabilistic delayed-fracture model based on a concept
wherein the length of the critical crack growth due to SCG is enough larger than the initial crack length. For the second
model, Model II, a new probabilistic model is derived on the basis of a concept wherein the critical cracks have widely ranging
lengths. Next, a four-point bending test using a wide range of stress rates was performed for soda glass and alumina ceramics.
We constructed fracture probability–strength–time diagrams (F–S–T diagrams) with the experimental results of both materials
using both models. The F–S–T diagrams described using Model II were in good agreement with plots of the fracture strength
and the fracture time of both materials more so than Model I. 相似文献
19.
Li KW Lian HB Cai JH Wang YT Lee KY 《Journal of nanoscience and nanotechnology》2011,11(12):11019-11022
The optimal carbon nanotube (CNT) bundles with a hexagonal arrangement were synthesized using thermal chemical vapor deposition (TCVD). To enhance the electron field emission characteristics of the pristine CNTs, the zinc oxide (ZnO) nanostructures coated on CNT bundles using another TCVD technique. Transmission electron microscopy (TEM) images showed that the ZnO nanostructures were grown onto the CNT surface uniformly, and the surface morphology of ZnO nanostructures varied with the distance between the CNT bundle and the zinc acetate. The results of field emissions showed that the ZnO nanostructures grown onto the CNTs could improve the electron field emission characteristics. The enhancement of field emission characteristics was attributed to the increase of emission sites formed by the nanostructures of ZnO grown onto the CNT surface, and each ZnO nanostructure could be regarded as an individual field emission site. In addition, ZnO-coated CNT bundles exhibited a good emission uniformity and stable current density. These results demonstrated that ZnO-coated CNTs is a promising field emitter material. 相似文献
20.
Kh. N. Vezirov 《Technical Physics Letters》1998,24(1):69-70
Experiments are described which permit the existence of an appreciable thermionic emission current from a photocathode to
be established and the dependence of the thermionic emission current density of the cathode on the temperature, magnetic field,
and current passed through the photocathode to be measured.
Pis’ma Zh. Tekh. Fiz. 24, 63–67 (January 26, 1998) 相似文献