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1.
Wen-Ching Shih Jian-Min Jeng Chin-Tze Huang Jyi-Tsong Lo 《Journal of Materials Science: Materials in Electronics》2011,22(9):1269-1273
In this study, the carbon nanoflakes (CNFs) fabricated by sputtering were chosen as the field emission emitters because of
their very sharp and thin edges which are potentially good electron field emission sites. The as-deposited CNFs were annealed
in the furnace under hydrogen atmosphere. The results showed that the optimum field emission properties with smaller turn-on
field and larger current density were obtained at annealing temperature of 600 °C for 10 min. The hydrogen thermal annealing
has chemical etching on the surface of the CNFs and produces appropriate emission site density to increase the emission current
density. The turn-on field was reduced from 6.7 to 5.8 V/μm and electric current density was increased from 22 to 187 μA/cm2 under 8 V/μm after hydrogen thermal annealing. 相似文献
2.
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
3.
Zinc oxide (ZnO) nanostructures were grown on vertically aligned carbon nanotubes (CNTs) using thermal chemical vapor deposition (CVD) to enhance the field emission characteristics. The shape of ZnO nanostructure was tapered. Scanning electron microscopy (SEM) image showed the ZnO nanostructures were grown onto CNT surface uniformly. The field electron emission of pristine CNTs and ZnO-coated CNTs were measured. The results showed that ZnO nanostructures grown onto CNTs could improve the field emission characteristics. The ZnO-coated CNTs had a threshold electric field at about 3.1 V/μm at 1.0 mA/cm2. The results demonstrated that the ZnO-coated CNT is an ideal field emitter candidate material. The stability of the field emission current was also tested. 相似文献
4.
Han Eol Lim 《Vacuum》2009,84(5):526-529
We have selectively fabricated carbon nanotubes (CNTs) emitter arrays with a micro mold in capillary (MIMIC) assisted process. The electron emitter growth site was fabricated by resist patterning using the MIMIC process. The pattern was uniformly transferred to the substrate and well aligned CNTs were grown. The emitter produces a turn-on field of 2.7 V/μm with a field emission current of 10 μA/cm2. The electron emission current can be controlled by emitter pattern width and pitch variation. 相似文献
5.
K. S. Kim H. Ryu G. E. Jang 《Journal of Materials Science: Materials in Electronics》2002,13(10):589-592
Carbon nanotubes (CNTs) were vertically well-grown on Ni/Cr-deposited glass substrates at 580 °C by ICPCVD and bias-assisted ICPHFCVD techniques. The vertically well-aligned CNTs showed multi-walled type with hollow structure. The measured critical current density on CNTs grown by the ICPCVD technique was 1.0×10–6 A cm–2 at 5 V m–1 of turn-on field and 7.7×10–5 A cm–2 at 7.8 V m–1 of the critical field. On the other hand, the critical current density on CNTs grown by the bias-assisted ICPHFCVD technique was 3.7×10–7 A cm–2 at 3 V m of turn-on field and 3.3×10–4 A cm–2 at 6.8 V m–1 of the critical field, respectively. On comparing the two processes, it can be concluded that CNTs grown by bias-assisted ICPHFCVD are more suitable than those grown by ICPCVD for the possible application of field emission displays (FEDs). 相似文献
6.
Wen-Ching Shih Jian-Min Jeng Jyi-Tsong Lo Huang-Chin Chen I-Nan Lin 《Journal of Materials Science: Materials in Electronics》2010,21(9):926-931
Carbon nanoflakes (CNFs) with corrugated geometry were synthesized using RF sputtering process with Ar/CH4 gas mixture. Transmission electron microscopic examination reveals that the introduction of H2 in sputtering chamber leads to the preferential etching of amorphous carbons, while maintaining integrity for the nano-crystalline
phases. The proportion of nano-sized crystalline clusters is thus increased, which improved the electron field emission (EFE)
properties of the materials, viz. with turn-on field of E
0 = 6.22 V/μm and FEE current density of J
e = 90.1 μA/cm2 at 11.0 V/μm. The cathodes made of screen printing of CNFs-Ag paste exhibit even better EFE properties than the as-deposited
CNFs. The EFE of the CNFs cathodes can be turned on at E
0 = 5.71 V/μm, achieving J
0 = 340.1 μA/cm2 at 11.0 V/μm applied field. These results showed that the CNFs are inheritantly more robust in device fabrication process
than the other carbon materials and thus possess better potential for electron field emitter applications. 相似文献
7.
It is the purpose of this study to evaluate the field emission property of carbon nanotubes (CNTs) prepared by microwave plasma-enhanced chemical vapor deposition (MPCVD) method. Nickel layer of 5 nm in thickness on 20-nm thickness titanium nitride film was transformed into discrete islands after hydrogen plasma pretreatment. CNTs were then grown up on Ni-coated areas by MPCVD. Through the practice of Taguchi method, superior CNT films with very low emission onset electric field, about 0.7 V/μm (at J = 10 μA/cm2), are attained without post-deposition treatment. It is found that microwave power has the most important influence on the field emission characteristics of CNT films. The increase of methane flow ratio will downgrade the degree of graphitization of CNT and thus its field emission characteristics. Scanning electron microscope and transmission electron microscopy (TEM) observation and energy dispersive X-ray spectrometer analysis reveal that CNT growth by MPCVD is based on tip-growth mechanism. TEM micrographs validate the hollow, bamboo-like structure of the multi-walled CNTs. 相似文献
8.
K. S. Kim H. Ryu G. E. Jang 《Journal of Materials Science: Materials in Electronics》2004,15(3):159-163
This paper presents a technique for the preparation of vertically grown carbon nanotubes (CNTs) by bias-assisted inductively coupled plasma hot-filament chemical vapor deposition. Purification of the CNTs using r.f. plasma in a one-step process, based on the different etching property of the metal tip is also discussed. The Ni at the tip of the CNTs was effectively removed by using r.f. plasma based on the different etching property. After purification CNTs show the multi-walled and hollow-type structure. The measured critical current density on CNTs with a Ni tip was 3.52×10–7 A cm–2 at 2.47 V m–1 turn-on field and 6.6×10–4 A cm–2 at 4.8 V m–1 of the critical field. On the other hand, the critical current density on purified CNTs after Ni removal by an r.f. source was 1.36×10–7 A cm–2 at 2.1 V m–1 turn-on field and 1.5×10–3 A cm–2 at 6 V m–1 of the critical field, respectively. 相似文献
9.
TiS3 nanobelt films, with widths of about 0.1–12 μm, thickness of about 20–250 nm, and lengths of up to 200 μm, have been grown
on Ti substrates by a surface-assisted chemical-vapor-transport at 450 °C for 8 h. The TiS3 nanobelt films were converted into TiS1.71 nanobelt films by pyrolysis in a vacuum at 600 °C for 2 h. The work functions of the two films were determined by ultraviolet
photoelectron spectroscopy measurements to be 4.60 and 4.44 eV, respectively. Preliminary field emission experiments using
the nanostructures as cold electron cathodes showed that both materials gave significant emission currents. The turn-on fields
(defined as the electric field required to produce a current density of 10 μA/cm2) were about 1.0 and 0.9 V/μm, respectively, whereas the threshold fields (defined as the electric field required to produce
a current density of 1 mA/cm2) were about 5.6 and 4.0 V/μm, respectively. These data reveal that both materials have potential applications in field emission
devices.
This article is published with open access at Springerlink.com 相似文献
10.
Well-aligned TiO2/Ti nanotube arrays were synthesized by anodic oxidation of titanium foil in 0.5 wt.% HF in various anodization voltages. The images of filed emission scanning electron microscopy indicate that the nanotubes structure parameters, such as diameter, wall thickness and density, can be controlled by adjusting the anodization voltage. The peaks at 25.3° and 48.0° of X-ray diffraction pattern illuminate that the TiO2 nanotube arrays annealed at 500 °C are mainly in anatase phase. The filed emission (FE) properties of the samples were investigated. A turn-on electric field 7.8 V/µm, a field enhancement factors approximately 870 and a highest FE current density 3.4 mA/cm2 were obtained. The emission current (2.3 mA/cm2 at 18.8 V/µm) was quite stable within 480 min. The results show that the FE properties of TiO2/Ti have much relation to the structure parameters. 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.
We report on the growth of carbon nanotubes on a glass substrate at a low temperature of 450 °C by plasma-enhanced chemical vapor deposition in the presence of a magnetic field. The growth of carbon nanotubes can be realized at 450 °C only when a magnetic field is applied to the substrate. Carbon nanotubes cannot be grown in the absence of a magnetic field at the same temperature. An NH3 plasma pretreatment significantly improved the uniformity of the grain size of the Ni catalyst under the magnetic field. The enhancement in the growth of CNTs at low temperature can be attributed to the magnetic moment pre-alignment of the ferromagnetic catalyst film under high magnetic field. A high emission current density of 20 mA/cm2 was obtained at 6 V/μm and a stable emission current was observed. This method permits the growth of carbon nanotubes directly on glass substrate at much more reliable low temperatures for the fabrication of high-density field emitter arrays. 相似文献
13.
Flower-like zinc oxide (ZnO) nanostructures with hexagonal crown were synthesized on a Si substrate by direct thermal evaporation of zinc power at a low temperature of 600 °C and atmospheric pressure. Field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy and photoluminescence were applied to study the structural characteristics and optical properties of the product. The result indicated that the flower-like product with many slender branches and hexagonal crowns at the ends were single-crystalline wurtzite structures and were preferentially oriented in the <001> direction. The photoluminescence spectrum demonstrated a strong UV emission band at about 386 nm and a green emission band at 516 nm. The field emission of the product showed a turn-on field of 3.0 V/µm at a current density of 0.1 μA/cm2, while the emission current density reached about 1 mA/cm2 at an applied field of 5.9 V/μm. 相似文献
14.
Field emission from oriented tin oxide rods 总被引:1,自引:0,他引:1
Tin oxide (SnO2) films were grown on silicon substrates by a wet chemical route. It was found from scanning electron microscopy investigations that oriented SnO2 rods normal to the substrates were obtained. Field emission studies were carried out in diode configuration in an all metal ultra high vacuum chamber at a base pressure ∼ 1.33 × 10− 8 mbar. The ‘onset’ field required to draw 0.1 μA/cm2 current density from the emitter cathode was found to be ∼ 3.4 V/μm for SnO2 rods. The field emission current and applied field follows the Folwer-Nordheim relationship in low field regime. The observed results indicate that the field emission characteristics of chemically grown SnO2 structures are comparable to the vapor grown nanostructures. 相似文献
15.
In this article, we showed that simple metal oxide coatings such as MoO3 can be an effective enhancer for carbon nanotubes (CNTs) in field emission (FE) performance. For comparison, the FE properties
of the pristine vertically aligned multi-walled CNTs with the metal oxide-coated CNTs were investigated. The metal oxide coating
of the pristine CNTs was carried out by metal–organic chemical vapor deposition (MOCVD) method at 400 °C using Mo(CO)6 as the precursor. The core–shell structure of the nanocomposite was studied by transmission electron microscopy (TEM). X-ray
photoelectron spectroscopy (XPS) results showed that the surface of the coating material was mainly MoO3. FE test indicated that the MoO3-coated CNTs film exhibited an enhanced performance than the pristine CNTs with a turn-on field of 1.33 V μm−1 and a field enhancement factor β estimated to be ~7000. Ultraviolet photoelectron spectroscopy (UPS) results confirmed a lower electron emission barrier height
for MoO3-coated CNTs than for the pristine CNTs. The mechanism of the enhanced FE performance is discussed based on Schottky barrier
effect. 相似文献
16.
Vertically aligned multi-walled carbon nanotubes have been grown on Ni-coated silicon substrates, by using either direct current diode or triode plasma-enhanced chemical vapor deposition at low temperature (around 620 °C). Acetylene gas has been used as the carbon source while ammonia and hydrogen have been used for etching. However densely packed (∼ 109 cm− 2) CNTs were obtained when the pressure was ∼ 100 Pa. The alignment of nanotubes is a necessary, but not a sufficient condition in order to get an efficient electron emission: the growth of nanotubes should be controlled along regular arrays, in order to minimize the electrostatic interactions between them. So a three dimensional numerical simulation has been developed to calculate the local electric field in the vicinity of the tips for a finite square array of nanotubes and thus to calculate the maximum of the electron emission current density as a function of the spacing between nanotubes. Finally the triode plasma-enhanced process combined with pre-patterned catalyst films (using different lithography techniques) has been chosen in order to grow regular arrays of aligned CNTs with different pitches in the micrometer range. The comparison between the experimental and the simulation data permits to define the most efficient CNT-based electron field emitters. 相似文献
17.
S. E. Valavan 《Journal of Materials Science: Materials in Electronics》2009,20(6):555-559
In this paper, we report the ferroelectric properties and leakage current characteristics of vanadium-doped PbZr0.53Ti0.47O3 (PZTV) films grown on various seed layers prepared by a sol–gel process. The PZTV multilayered film of ~250-nm-thick showed
excellent ferroelectric properties, with a large remnant polarization (P
r) of ~30 μC/cm2 (E
c ~ 90 kV/cm), a high saturation polarization (P
s) of ~85 μC/cm2 for an applied field of 1,000 kV/cm, fatigue-free characteristics of up to ≥ 1010 switching cycles, and a low leakage current density of 7 × 10−8 A/cm2 at 100 kV/cm. X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) investigations
indicated that PZTV films grown on PbZr0.53Ti0.47O3/PbLa0.05TiO3 (PZT/PLT) seed layers exhibited a dense, well-crystallized microstructure with random orientations and a rather smooth surface
morphology. 相似文献
18.
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
19.
Beihai Ma Manoj Narayanan Sheng Tong U. Balachandran 《Journal of Materials Science》2010,45(1):151-157
We have grown ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films on Hastelloy C276 (HC) substrates by chemical solution deposition. Samples of 1.15-μm-thick PLZT films were
prepared on HC with and without lanthanum nickel oxide (LNO) films as an intermediate buffer layer. On samples with and without
LNO buffers at room temperature, we measured dielectric constants of ≈1,300 and ≈450 and loss tangents of ≈0.06 and ≈0.07,
respectively. For PLZT films grown on HC with LNO buffer, the dielectric constant increases, while the dielectric loss decreases,
with increasing temperature. A dielectric constant of ≈2,000 and loss of ≈0.05 were observed at 150 °C. Samples with LNO buffer
also exhibited slimmer hysteresis loops and lower leakage current density when compared to samples without LNO buffer. The
following results were measured on samples with and without LNO buffers: remanent polarization (P
r) values of 21.3 and 36.4 μC/cm2, coercive electric field (E
c) values of 41 and 173 kV/cm, and leakage current densities of ≈1.1 × 10−8 and ≈1.6 × 10−7 A/cm2, respectively. The energy storage capability was measured at ≈65 J/cm3 for the PLZT film-on-foil capacitor deposited on HC with LNO buffer. 相似文献
20.
Nitrogenated carbon nanotips (NCNTPs) with different structures were synthesized by plasma-enhanced hot filament chemical vapor deposition using methane, hydrogen and nitrogen as the reactive gases. The structures and compositions of the NCNTPs were studied by field emission scanning electron microscopy (FESEM), micro-Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The XPS spectra reveal that nitrogen is incorporated into the carbon nanotips to form the NCNTPs under plasma condition. The Raman spectra and FESEM images show that the NCNTPs are amorphous structure and their morphologies change with the change in deposition conditions, respectively. The electron field emission (EFE) from the NCNTPs was measured and the EFE results indicate that the NCNTPs with the smooth surfaces and high density can emit a current density of 3 × 103 μA/cm2 at an electric field of 7.2 V/μm, which exhibits better EFE characteristic than the NCNTPs with the carbon nanowires on their surfaces due to small amount of oxygen adsorbed on the smooth surfaces of NCNTPs. According to the possible structures of nitrogen in sp2 cluster in rings, the EFE enhancement of the NCNTPs compared with pure carbon nanotips was studied. The high emission current density (3 × 103 μA/cm2) at low field (7.2 V/μm) suggests that the NCNTPs can serve as effective electron emission sources for numerous applications. 相似文献