共查询到20条相似文献,搜索用时 31 毫秒
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.
S. Mridha M. Dutta Durga Basak 《Journal of Materials Science: Materials in Electronics》2009,20(Z1):376-379
A series of n-ZnO/p-Si thin film heterojunctions have been fabricated by a low cost sol–gel technique for different ZnO film thicknesses and
the dark as well as photo current–voltage (I–V) characteristics have been investigated in details. The heterojunction with ZnO thickness of 0.46 μm shows the best diode
characteristics in terms of rectification ratio, I
F/I
R = 5.7 × 103 at 5 V and reverse leakage current density, J
R = 7.6 × 10−5 A cm−2 at −5 V. From the photo I–V curves and wavelength dependent photocurrent of the heterojunctions, it is found that the junction with 0.46 μm ZnO thickness
shows the highest sensitivity towards both UV and visible lights. 相似文献
3.
The electron field emission (EFE) properties of silicon nanostructures (SiNSs) coated with ultra-nanocrystalline diamond (UNCD) were characterized. The SiNS, comprising cauliflower-like grainy structure and nanorods, was generated by reaction of a Si substrate with an Au film at 1000 °C, and used as templates to grow UNCD. The UNCD films were deposited by microwave plasma-enhanced chemical vapour deposition (MPECVD) using methane and argon as reaction gases. The UNCD films can be grown on the SiNS with or without ultrasonication pretreatment with diamond particles. The EFE properties of the SiNS were improved by adding an UNCD film. The turn-on field (E0) decreased from 17.6 V/μm for the SiNS to 15.2 V/μm for the UNCD/SiNS, and the emission current density increased from 0.095 to 3.8 mA/cm2 at an electric field of 40 V/μm. Ultrasonication pretreatments of SiNS with diamond particles varied the structure and EFE properties of the UNCD/SiNS. It is shown that the ultrasonication pretreatment degraded the field emission properties of the UNCD/SiNS in this study. 相似文献
4.
Ken Hirota Yuichi Takaura Masaki Kato Yoshinari Miyamoto 《Journal of Materials Science》2007,42(13):4792-4800
Dense Al2O3-based composites (≥99.0% of theoretical) dispersed with carbon nanofibers (CNFs) were fabricated using the pulsed electric-current
pressure sintering (PECPS) for 5 min at 1300°C and 30 MPa in a vacuum. The dispersion of CNFs into the matrix depended much
on the particle size of the starting Al2O3 powders. Mechanical properties of the composites were evaluated in relation with their microstructures; high values of three-point
bending strength σb (∼800 MPa) and fracture toughness K
IC (∼5 MPa·m1/2) were attained at the composition of CNF/Al2O3 = 5:95 vol%, which σb and K
IC values were ∼25% and ∼5%, respectively, higher than those of monolithic Al2O3. This might be due to the small Al2O3 grains (1.6 μm) of dense sintered compacts compared with that (4.4 μm) for the pure Al2O3 ceramics, resulting from the suppression of grain growth during sintering induced by uniformly dispersed CNFs in the matrix.
Electrical resistivity of CNF/Al2O3 composites decreased rapidly from >1015 to ∼2.1 × 10−2 Ωm (5vol%CNF addition), suggesting the machinability of Al2O3-based composites by electrical discharge machining.
相似文献
Ken HirotaEmail: |
5.
Choon-W. Nahm 《Journal of Materials Science: Materials in Electronics》2012,23(2):457-463
The effect of sintering process on microstructure, electrical properties, and ageing behavior of ZnO–V2O5–MnO2–Nb2O5 (ZVMN) varistor ceramics was investigated at 875–950 °C. The sintered density decreased from 5.52 to 5.44 g/cm3 and the average grain size increased from 4.4 to 9.6 μm with the increase of sintering temperature. The breakdown field (E1 mA) decreased from 6991 to 943 V/cm with the increase of sintering temperature. The ZVMN varistor ceramics sintered at 900 °C
led to surprisingly high nonlinear coefficient (α = 50). The donor concentration (Nd) increased from 3.33 × 1017 cm−3 to 7.64 × 1017 cm−3 with the increase of sintering temperature and the barrier height (Φb) exhibited the maximum value (1.07 eV) at 900 °C. Concerning stability, the varistors sintered at 925 °C exhibited the most
stable accelerated ageing characteristics, with %ΔE1 mA = 1.5% and %Δα = 13.3% for DC accelerated ageing stress of 0.85 E1 mA/85 °C/24 h. 相似文献
6.
Laijun Liu Yanmin Huang Yunhua Li Danping Shi Shaoying Zheng Shuangshuang Wu Liang Fang Changzheng Hu 《Journal of Materials Science》2012,47(5):2294-2299
In order to conciliate dielectric and non-Ohmic properties of CaCu3Ti4O12 (CCTO) ceramics, NiO, SnO2, SiO2, and Al2O3 were added as sintering aids to promote the grain growth of CCTO ceramics. Microstructure, dielectric properties, and non-Ohmic
behavior of the CCTO ceramics were investigated. Among them, NiO-modified CCTO exhibits good dielectric and non-Ohmic properties
(ε = 69833, tanδ = 0.073, α = 3.66 and E
B = 296.7 V/cm), due to NiO is also one of giant dielectric materials. Therefore, it is suitable for applying semiconductor
circuits. The relationship between electrical current density (J) and electrical field (E) demonstrated that Schottky barrier should exist at grain boundaries. Non-linear coefficient α was directly proportional to the height of barrier. Depressing barrier width would improve significantly dielectric permittivity
but decrease breakdown voltage. 相似文献
7.
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
8.
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
9.
Hua Wang Xiaodan Huang Jiwen Xu Ling Yang Shangju Zhou 《Journal of Materials Science: Materials in Electronics》2012,23(1):234-237
Bi4Ti3−xNbxO12 ferroelectric thin films were fabricated on p-Si substrates by magnetron sputtering. The effects of Nb doping on microstructure
and properties of Bi4Ti3−xNbxO12 films were investigated. Bi4Ti3−xNbxO12 films had the same structure as Bi4Ti3O12 with smaller and more uniform grains. The dielectric and ferroelectric properties of Bi4Ti3−xNbxO12 films were improved by Nb doping. Bi4Ti3−xNbxO12 films have better dielectric and ferroelectric properties with P
r = 16.5 μC/cm2, E
C < 100 kV/cm, ε
r > 290, low dielectric loss (<0.9%) and clockwise C–V curves with a memory window of 0.9 V when x = 0.03–0.045, while an excessive
Nb doping would lead to bad dielectric and ferroelectric properties. 相似文献
10.
Vitaliy Syvokon Yury Monarkha Kostyantin Nasyedkin Sviatoslav Sokolov 《Journal of Low Temperature Physics》2007,148(3-4):169-174
Mobility of surface electrons (SE) on liquid helium at low temperatures (T≃0.52 K) is studied as a function of the driving electric field E
∥
in the range 1–25 mV/cm. The experimental conditions correspond approximately to effective electron temperatures T
e
≃1–12 K. The measurements are performed for SE with the surface electron density n
s
=1.46×108 cm−2 at different holding electric fields E
⊥
=200–1400 V/cm. The mobility is observed to be an increasing function of the driving field. The function depends strongly
on the holding electric field applied. The experimental results are in reasonable agreement with theoretical curves calculated
using the force-balance equation method expressing the mobility in terms of the dynamical structure factor of SE. 相似文献
11.
Dongyun Guo Changyong Liu Chuanbin Wang Qiang Shen Lianmeng Zhang 《Journal of Materials Science: Materials in Electronics》2011,22(2):130-135
Bi3.6Ho0.4Ti3O12 and (Bi0.9Ho0.1)4−x/3Ti3−x
V
x
O12 (BHTV) (x = 0.3, 1.2, 3.0 and 6.0%) thin films were prepared on Pt/Ti/SiO2/Si substrates by sol–gel method. The effect of V content on their microstructure and ferroelectric properties were investigated.
All the BHTV samples consisted of the single phase of Bi-layered Aurivillius phase. The B-site substitution with high-valent
cation of V5+, in Bi3.6Ho0.4Ti3O12 films, enhanced the remanent polarizations (2Pr) and reduced the coercive field (2Ec). The BHTV film with x = 0.3% exhibited the better electrical properties with 2Pr 45.5 μC/cm2, 2Ec 257 kV/cm, good insulting behavior, as well as the fatigue-free characteristic. 相似文献
12.
Changyong Liu Dongyun Guo Chuanbin Wang Qiang Shen Lianmeng Zhang 《Journal of Materials Science: Materials in Electronics》2012,23(3):802-806
Bi4-xNdxTi3O12 (BNT-x, x = 0, 0.25, 0.50, 0.75 and 1.0) thin films were prepared on Pt/Ti/SiO2/Si substrates by a sol–gel method. The microstructure, ferroelectric and dielectric properties of BNT-x thin films were investigated.
The single-phase BNT-x thin films were obtained. With increasing Nd content, the preferred orientation changed from random
to (117) and surface morphologies changed from the mixture of rod- and plate-like grains to rod-like grains. The Nd substitution
improved the ferroelectric and dielectric properties of BTO films. BNT-x films showed better electrical properties at x = 0.50—1.0.
BNT-0.75 film exhibited the best electrical properties with remanent polarization (2P
r) of 26.6 μC/cm2, dielectric constant (ε
r) of 366 (at 1 MHz), dielectric loss (tanδ) of 0.034 (at 1 MHz), leakage current density (J) of ±3.0 × 10−6 A/cm2 (at ± 5 V) and fatigue-free characteristics. 相似文献
13.
Xiaokun Song Dan Hong Ying Wang Huaran Liu Linfei Liu Yijie Li 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1793-1796
It is known that the tape’s temperature controlled by a close substrate heater will still deviate after the deposition process.
In this work, we deposited YBa2Cu3O7−δ
(YBCO) films on RABiTS substrates with multilayer CeO2/YSZ/CeO2 buffer layers by pulsed laser deposition (PLD) under a different distribution of temperature deviation in order to improve
it. Thermocouples were applied to exactly measure the temperature. X-ray diffraction (XRD) and scanning electron microscopy
(SEM) were used to inspect c-axis oriented crystals and surface morphology of YBCO films. Through this work, we found that
the even shape is best. Under the temperature deviation with the best shape, a transport J
c
of 3.2×106 A/cm2 and I
c
=240 A was obtained for a 0.75 μm thick YBCO film on CeO2/YSZ/CeO2-bufferd RABiTS Ni–W alloy. 相似文献
14.
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
15.
Y. Y. Zhang J. L. Liu Y. X. Zhu Y. Shang M. Yu X. Huang 《Journal of Materials Science》2009,44(13):3364-3369
Nanocrystalline SrCO3:Tb3+ phosphor layers were coated on monodisperse and spherical polystyrene particles by a typical hydrothermal synthesis without
further annealing treatment, resulting in the formation of core-shell-structured polystyrene@SrCO3:Tb3+ particles. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence,
as well as lifetimes were employed to characterize the resulting composite particles. Under ultraviolet excitation, the polystyrene@SrCO3:Tb3+ phosphors show the characteristic 5D4–7F
J
(J = 6, 5, 4, 3) emission lines with green emission 5D4–7F5 (544 nm) as the most prominent group. The obtained core-shell phosphors are potentially applied in fluorescent lamps. 相似文献
16.
Structural, optical, and electric properties of BNT–BT0.08 thin films processed by sol–gel technique
Marin Cernea Lucian Trupina Cristina Dragoi Aurelian-Catalin Galca Liliana Trinca 《Journal of Materials Science》2012,47(19):6966-6971
Thin films with the composition [(Bi0.5Na0.5)TiO3]0.92–[BaTiO3]0.08 (hereafter BNT–BT0.08) were deposited on Pt–Si by spin-coating from a stable sol precursor. The BNT–BT0.08 film, crystallized on the Bi0.5Na0.5TiO3 rhombohedral lattice, was obtained after annealing the film-gel at 700 °C. The films have a smooth surface (Rms = 2.76 nm) and grains with ferroelectric domains. The film showed a bandgap of 3.25 eV and a refractive index of 2.20 at a wavelength of 630 nm. The dielectric characteristics of BNT–BT0.08 thin films were measured at room temperature and 10 kHz the dielectric constant (ε r) was 243 and the loss tangent (tanδ) was 0.38. The remnant polarization (P r) was 0.87 μC/cm2 and the coercive field (E c) was 220 kV/cm at 10 kHz and room temperature. The current density was approximately 2.7 × 10−5 A/cm2 at low electric fields (100 kV/cm). BNT–BT0.08 thin films shown piezoelectric properties (d 33eff = 100 pm/V) comparable to those of PZT thin films. 相似文献
17.
The Sn–3.5 wt% Ag eutectic alloy was directionally solidified upward with a constant growth rate (V = 16.5 μm/s) at different temperature gradients (G = 1.43–4.28 K/mm) and with a constant temperature gradient (G = 3.93 K/mm) at different growth rates (V = 8.3–500 μm/s) in a Bridgman-type directional solidification furnace. The rod spacings (longitudinal section, λ
L
and transverse section, λ
T
) and mechanical properties (microhardness, HV and ultimate tensile strength, σ
UTS
) of Sn–3.5 wt% Ag eutectic alloy were measured. The dependency of the microhardness, ultimate tensile strength on the temperature
gradient, growth rate and rod spacings were determined. According to experimental results, the microhardness and ultimate
tensile strength of the solidified samples increase with increasing G and V, but decrease with the increasing the rod spacing. 相似文献
18.
Pouponneau P Savadogo O Napporn T Yahia L Martel S 《Journal of materials science. Materials in medicine》2011,22(2):237-245
Once placed in a magnetic field, smart magnetic materials (SMM) change their shape, which could be use for the development
of smaller minimally invasive surgery devices activated by magnetic field. However, the potential degradation and release
of cytotoxic ions by SMM corrosion has to be determined. This paper evaluates the corrosion resistance of two SMM: a single
crystal Ni–Mn–Ga alloy and Tb0.27Dy0.73Fe1.95 alloy. Ni–Mn–Ga alloy displayed a corrosion potential (E
corr) of −0.58 V/SCE and a corrosion current density (i
corr) of 0.43 μA/cm2. During the corrosion assay, Ni–Mn–Ga sample surface was partially protected; local pits were formed on 20% of the surface
and nickel ions were mainly found in the electrolyte. Tb0.27Dy0.73Fe1.95 alloy exhibited poor corrosion properties such as E
corr of −0.87 V/SCE and i
corr of 5.90 μA/cm2. During the corrosion test, this alloy was continuously degraded, its surface was impaired by pits and cracks extensively
and a high amount of iron ions was measured in the electrolyte. These alloys exhibited low corrosion parameters and a selective
degradation in the electrolyte. They could only be used for medical applications if they are coated with high strain biocompatible
materials or embedded in composites to prevent direct contact with physiological fluids. 相似文献
19.
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
20.
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