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1.
Thermal stability of Mg2Si epitaxial film formed on Si(111) substrate by solid phase reaction 下载免费PDF全文
A single crystalline Mg2 Si film was formed by solid phase reaction(SPR) of a Si(111) substrate with an Mg overlayer capped with an oxide layer(s),which was enhanced by post annealing from room temperature to 100 ℃in a molecular beam epitaxy(MBE) system.The thermal stability of the Mg2 Si film was then systematically investigated by post annealing in an oxygen-radical ambient at 300℃,450℃ and 650 ℃,respectively.The Mg2 Si film stayed stable until the annealing temperature reached 450 ℃ then it transformed into amorphous MgO x attributed to the decomposition of Mg2 Si and the oxidization of dissociated Mg. 相似文献
2.
This paper investigates the infrared absorption spectra of oxygen-related complexes in silicon crystals irradiated with
electron (1.5~MeV) at 360~K. Two groups of samples with low [Oi]=6.9× 1017~cm-3 and high [ Oi]=1.06× 1018~cm-3 were used. We found that the
concentration of the VO pairs have different behaviour to the
annealing temperature in different concentration of oxygen specimen,
it is hardly changed in the higher concentration of oxygen specimen. It
was also found that the concentration of VO2 in lower concentration
of oxygen specimen gets to maximum at 450~℃ and then
dissapears at 500~℃, accompanied with the appearing of
VO3. For both kinds of specimens, the concentration of VO3
reachs to maximum at 550~℃ and does not disappear
completely at 600~℃. 相似文献
3.
Superhydrophobic surfaces via controlling the morphology of ZnO micro/nano complex structure 下载免费PDF全文
ZnO micro/nano complex structure films, including reticulate papillary nodes, petal-like and flake-hole, have been self-assembled by a hydrothermal technique at different temperatures without metal catalysts. The wettability of the above film surfaces was modified with a simple coating of heptadecafluorodecyltrimethoxy-silane in toluene. After modifying, the surface of ZnO film grown at 50~${^\circ}$C was converted from superhydrophilic with a water contact angle lower than 5$^{\circ}$ to superhydrophobic with a water contact angle of 165$^{\circ}$. Additionally, the surface of reticulate papillary nodes ZnO film grown at 100~${^\circ}$C had excellent superhydrophobicity, with a water contact angle of 173$^{\circ}$ and a sliding angle lower than 2$^{\circ}$. Furthermore, the water contact angle on the surface of petal-like and flake-hole ZnO films grown at 150~${^\circ}$C and 200~${^\circ}$C were found to be 140$^{\circ}$ and 120$^{\circ}$, respectively. The wettability for the samples was found to depend strongly on the surface morphology which results from the growth temperature. 相似文献
4.
Effects of concentration and annealing on the performance of regioregular poly(3-hexylthiophene) field-effect transistors 下载免费PDF全文
This paper investigates the effects of concentration on the
crystalline structure, the morphology, and the charge carrier
mobility of regioregular poly(3-hexylthiophene) (RR-P3HT)
field-effect transistors (FETs). The RR-P3HT FETs with RR-P3HT as an
active layer with different concentrations of RR-P3HT solution from
0.5~wt% to 2~wt% are prepared. The results indicate that the
performance of RR-P3HT FETs improves drastically with the increase
of RR-P3HT weight percentages in chloroform solution due to the
formation of more microcrystalline lamellae and bigger nanoscale
islands. It finds that the field-effect mobility of RR-P3HT FET with
2~wt% can reach 5.78× 10^-3~cm2/Vs which is higher
by a factor of 13 than that with 0.5~wt%. Further, an appropriate
thermal annealing is adopted to improve the performance of RR-P3HT
FETs. The field-effect mobility of RR-P3HT FETs increases
drastically to 0.09~cm2/Vs by thermal annealing at
150~℃, and the value of on/off current ratio can reach
10^4. 相似文献
5.
Investigations on spectroscopic parameters, vibrational levels, classical turning points and inertial rotation and centrifugal distortion constants for the X1∑+g state of sodium dimer 下载免费PDF全文
The density functional theory (B3LYP, B3P86) and the quadratic
configuration-interaction method including single and double
substitutions (QCISD(T), QCISD) presented in Gaussian03 program
package are employed to calculate the equilibrium internuclear
distance $R_{\rm e}$, the dissociation energy $D_{\rm e }$ and the
harmonic frequency $\omega _{\rm e}$ for the $X{}^{1}\Sigma^{ +
}_{\rm g}$ state of sodium dimer in a number of basis sets. The
conclusion is gained that the best $R_{\rm e}$, $D_{\rm e}$ and
$\omega _{\rm e}$ results can be attained at the
QCISD/6-311G(3df,3pd) level of theory. The potential energy curve at
this level of theory for this state is obtained over a wide
internuclear separation range from 0.16 to 2.0~nm and is fitted to
the analytic Murrell--Sorbie function. The spectroscopic parameters
$D_{\rm e}$, $D_{0}$, $R_{\rm e}$, $\omega _{\rm e}$,
$\omega _{\rm e}\chi _{\rm e}$,
$\alpha _{\rm e}$
and $B_{\rm e}$ are calculated to be 0.7219~eV,
0.7135~eV, 0.31813~nm, 151.63~cm$^{ - 1}$, 0.7288~cm$^{ - 1}$,
0.000729~cm$^{ - 1}$ and 0.1449~cm$^{ - 1}$, respectively, which are in good
agreement with the measurements. With the potential obtained at the
QCISD/6-311G(3df,3pd) level of theory, a total of 63 vibrational
states is found when $J=0$ by solving the radial Schr\"{o}dinger equation
of nuclear motion. The vibrational level, corresponding classical turning
point and inertial rotation constant are computed for each vibrational
state. The centrifugal distortion constants
($D_{\upsilon }\, H_{\upsilon }$,
$L_{\upsilon }$, $M_{\upsilon }$, $N_{\upsilon }$ and $O_{\upsilon })$ are
reported for the first time for the first 31 vibrational states when $J=0$. 相似文献
6.
Study on spectroscopic parameters and molecular constants of HCl(X~1Σ~+) molecule by using multireference configuration interaction approach 下载免费PDF全文
Equilibrium internuclear separations, harmonic frequencies
and potential energy curves (PECs) of HCl($X^{1}\Sigma ^{ + })$
molecule are investigated by using the highly accurate valence
internally contracted multireference configuration interaction
(MRCI) approach in combination with a series of
correlation-consistent basis sets in the valence range. The PECs are
all fitted to the Murrell--Sorbie function, and they are used to
accurately derive the spectroscopic parameters ($D_{\rm e}$,
$D_{0}$, $\omega_{\rm e}\chi_{\rm e}$, $\alpha_{\rm e}$ and $B_{\rm
e})$. Compared with the available measurements, the PEC obtained at
the basis set, aug-cc-pV5Z, is selected to investigate the
vibrational manifolds. The constants $D_{0}$, $D_{\rm e}$, $R_{\rm
e}$, $\omega_{\rm e}$, $\omega_{\rm e}\chi_{\rm e}$, $\alpha_{\rm
e}$ and $B_{\rm e}$ at this basis set are 4.4006~eV, 4.5845~eV,
0.12757~nm, 2993.33~cm$^{ - 1}$, 52.6273~cm$^{ - 1}$, 0.2981~cm$^{ -
1}$ and 10.5841~cm$^{ - 1}$, respectively, which almost perfectly
conform to the available experimental results. With the potential
determined at the MRCI/aug-cc-pV5Z level of theory, by numerically
solving the radial Schr\"{o}dinger equation of nuclear motion in the
adiabatic approximation, a total of 21 vibrational levels are
predicted. Complete vibrational levels, classical turning points,
inertial rotation and centrifugal distortion constants are
reproduced, which are in excellent agreement with the available
Rydberg--Klein--Rees data. Most of these theoretical vibrational
manifolds are reported for the first time to the best of our
knowledge. 相似文献
7.
Large scale, high density boron carbide nanowires have been synthesized by using an improved carbothermal reduction method with B/B203/C powder precursors under an argon flow at 1100℃. The boron carbide nanowires are 5-10 μm in length and 80-100 nm in diameter. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) characterizations show that the boron carbide nanowire has a B4C rhombohedral structure with good crystallization. The Raman spectrum of the as-grown boron carbide nanowires is consistent with that of a B4C structure consisting of B11C icosahedra and C-B-C chains. The room temperature photoluminescence spectrum of the boron carbide nanowires exhibits a visible range of emission centred at 638 nm. 相似文献
8.
This paper reports that the m-plane GaN layer is grown on (200)-plane LiAlO2 substrate by metal-organic chemical wpour deposition (MOCVD) method. Tetragonal-shaped crystallites appear at the smooth surface. Raman measurement illuminates the compressive stress in the layer which is released with increasing the layer's thickness. The high transmittance (80%), sharp band edge and excitonic absorption peak show that the GaN layer has good optical quality. The donor acceptor pair emission peak located at -3.41 eV with full-width at half maximum of 120 meV and no yellow peaks in the photoluminescence spectra partially show that no Li incorporated into GaN layer from the LiAlO2 substrate. 相似文献
9.
GaN layers with different polarities prepared by radio frequency molecular beam epitaxy and characterized by Raman scattering 下载免费PDF全文
GaN layers with different polarities have been prepared by radio-frequency
molecular beam epitaxy (RF-MBE) and characterized by Raman
scattering. Polarity control are realized by controlling
Al/N flux ratio during high temperature AlN buffer growth. The Raman results
illustrate that the N-polarity GaN films have frequency shifts at $A_{1}$(LO)
mode because of their high carrier density; the forbidden $A_{1}$(TO) mode
occurs for mixed-polarity GaN films due to the destroyed translation
symmetry by inversion domain boundaries (IDBS); Raman spectra for
Ga-polarity GaN films show that they have neither frequency shifts mode nor forbidden
mode. These results indicate that Ga-polarity GaN films have a better
quality, and they are in good agreement with the results obtained from the
room temperature Hall mobility. The
best values of Ga-polarity GaN films are 1042 cm$^{2}$/Vs with a carrier
density of 1.0$\times $10$^{17}$~cm$^{ - 3}$. 相似文献
10.
The fabrication of nickel silicide ohmic contacts to n-type 6H-silicon carbide 总被引:1,自引:0,他引:1 下载免费PDF全文
This paper reports that the nickel silicide ohmic contacts to n-type
6H-SiC have been fabricated. Transfer length method test patterns
with NiSi/SiC and NiSi硅化镍;欧姆触点;n型碳化硅;制造;能带;带隙 Project supported by the National Basic Research Program of China (Grant
No~2002CB311904), the
National Defense Basic Research Program of China (Grant No~51327010101) and
the National Natural Science Foundation of China (Grant No~60376001). 2006-09-192006-10-30 This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi2/SiC structure axe formed on N-wells created by N^+ ion implantation into Si-faced p-type 6H-SiC epilayer respectively. NiSi and NiSi2 films are prepared by annealing the Ni and Si films separately deposited. A two-step annealing technology is performed for decreasing of oxidation problems occurred during high temperature processes. The specific contact resistance Pc of NiSi contact to n-type 6H-SiC as low as 1.78× 10^-6Ωcm^2 is achieved after a two-step annealing at 350 ℃for 20 min and 950℃ for 3 min in N2. And 3.84×10-6Ωcm^2 for NiSi2 contact is achieved. The result for sheet resistance Rsh of the N+ implanted layers is about 1210Ω/□. X-ray diffraction analysis shows the formation of nickel silicide phases at the metal/n-SiC interface after thermal annealing. The surfaces of the nickel silicide after thermal annealing are analysed by scanning electron microscope. 相似文献
11.
The effect of single A1GaN interlayer on the structural properties of GaN epilayers grown on Si (111) substrates 下载免费PDF全文
High-quality and nearly crack-free GaN epitaxial layer was obtained
by inserting a single AlGaN interlayer between GaN epilayer and
high-temperature AlN buffer layer on Si (111) substrate by
metalorganic chemical vapor deposition. This paper investigates the
effect of AlGaN interlayer on the structural properties of the
resulting GaN epilayer. It confirms from the optical microscopy and
Raman scattering spectroscopy that the AlGaN interlayer has a
remarkable effect on introducing relative compressive strain to the
top GaN layer and preventing the formation of cracks. X-ray
diffraction and transmission electron microscopy analysis reveal
that a significant reduction in both screw and edge threading
dislocations is achieved in GaN epilayer by the insertion of AlGaN
interlayer. The process of threading dislocation reduction in both
AlGaN interlayer and GaN epilayer is demonstrated. 相似文献
12.
Elastic collisions between Si and D atoms at low temperatures and accurate analytic potential energy function and molecular constants of the SiD(χ^2П) radical 下载免费PDF全文
Interaction potential of the SiD(X2Π) radical is constructed by using the CCSD(T) theory in combination with the largest correlation-consistent quintuple basis set augmented with the diffuse functions in the valence range. Using the interaction potential, the spectroscopic parameters are accurately determined. The present D0, De, Re, ωe, αe and Be values are of 3.0956 eV, 3.1863 eV, 0.15223 nm, 1472.894 cm-1, 0.07799 cm-1 and 3.8717 cm-1, respectively, which are in excellent agreement with the measurements. A total of 26 vibrational states is predicted when J=0 by solving the radial Schro¨dinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J=0 are reported for the first time, which are in good accord with the available experiments. The total and various partial-wave cross sections are calculated for the elastic collisions between Si and D atoms in their ground states at 1.0×10-11–1.0×10-3 a.u. when the two atoms approach each other along the SiD(X2Π) potential energy curve. Four shape resonances are found in the total elastic cross sections, and their resonant energies are of 1.73×10-5, 4.0×10-5, 6.45×10-5 and 5.5×10-4 a.u., respectively. Each shape resonance in the total elastic cross sections is carefully investigated. The results show that the shape of the total elastic cross sections is mainly dominated by the s partial wave at very low temperatures. Because of the weakness of the shape resonances coming from the higher partial waves, most of them are passed into oblivion by the strong s partial-wave elastic cross sections. 相似文献
13.
14.
A new transition metal diphosphide α-MoP2 synthesized by a high-temperature and high-pressure technique 下载免费PDF全文
Xiaolei Liu 《中国物理 B》2023,32(1):18102-018102
Monoclinic $\alpha $-MoP$_{2}$, with the OsGe$_{2}$-type structure (space group $C2/m$, $Z = 4$) and lattice parameters $a = 8.7248(11) $ Å, $b = 3.2322(4) $ Å, $c = 7.4724(9) $ Å, and $\beta =119.263^\circ $, was synthesized under a pressure of 4 GPa at a temperature between 1100 ${^\circ}$C and 1200 ${^\circ}$C. The structure of $\alpha $-MoP$_{2}$ and its relationship to other transition metal diphosphides are discussed. Surprisingly, the ambient pressure phase orthorhombic $\beta $-MoP$_{2}$ (space group Cmc2$_{1}$) is denser in structure than $\alpha $-MoP$_{2}$. Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition from $\beta $-MoP$_{2}$ to $\alpha $-MoP$_{2}$, suggesting that $\alpha $-MoP$_{2}$ is a stable phase at ambient conditions; this is also supported by the total energy and phonon calculations. 相似文献
15.
Effect of annealing on photoluminescence and microstructures of InGaN/GaN multi-quantum well with Mg-doped p-type GaN 总被引:3,自引:0,他引:3 下载免费PDF全文
InGaN/GaN multi-quantum well structure with Mg-doped p-type GaN was grown by low-pressure metalorganic vapour phase epitaxy. After rapid-thermal-annealing at 700 and 900${^\circ}$C, both the red-shift and the blue-shift of the photoluminescence (PL) peak, the decreased and the enhancement of the PL intensity were observed. The transmission electron microscopic images showed that InGaN multi-quantum-dots-like (MQD-like) structures with dimensions less than 5$\tm$10nm were formed in InGaN wells. The changes of PL spectra could be tentatively attributed to the competition between the red-shift mechanism of the quantum-confined Stark effect and the blue-shift mechanism of the quantum size effect due to MQD-like structures. 相似文献
16.
Nanosecond-time-resolved infrared spectroscopic study of fast relaxation kinetics of protein folding by means of laser-induced temperature-jump 下载免费PDF全文
Elucidating the initial kinetics of folding pathways is critical to the understanding of the protein folding mechanism. Transient infrared spectroscopy has proved a powerful tool to probe the folding kinetics. Herein we report the construction of a nanosecond laser-induced temperature-jump (T-jump) technique coupled to a nanosecond timeresolved transient mid-infrared (mid-IR) spectrometer system capable of investigating the protein folding kinetics with a temporal resolution of 50 ns after deconvolution of the instrumental response function. The mid-IR source is a liquid N2 cooled CO laser covering a spectral range of 5.0μm (2000 cm^-1)-6.5μm (1540 cm^-1). The heating pulse was generated by a high pressure H2 Raman shifter at wavelength of 1.9μm. The maximum temperature-jump could reach as high as 26±1℃. The fast folding/unfolding dynamics of cytochrome C was investigated by the constructed system, providing an example. 相似文献
17.
High energy electron radiation effect on Ni and Ti/4H-SiCSchottky barrier diode at room temperature 下载免费PDF全文
This paper reports that Ni and Ti/4H-SiC Schottky barrier diodes
(SBDs) were fabricated and irradiated with 1~MeV electrons up to a
dose of 3.43×1014~e/cm2. After radiation, the Schottky
barrier height φ B of the Ni/4H-SiC SBD increased from
1.20~eV to 1.21~eV, but decreased from 0.95~eV to 0.94~eV for the
Ti/4H-SiC SBD. The degradation of φ B could be
explained by interface states of changed Schottky contacts. The
on-state resistance RS of both diodes increased with the
dose, which can be ascribed to the radiation defects. The reverse
current of the Ni/4H-SiC SBD slightly increased, but for the Ti/4H-SiC
SBD it basically remained the same. At room temperature,
φ B of the diodes recovered completely after one week,
and the RS partly recovered. 相似文献
18.
The Ni/4H-SiC Schottky barrier diodes (SBDs) and transfer length
method (TLM) test patterns of Ni/4H-SiC Ohmic contacts were
fabricated, and irradiated with 1~MeV electrons up to a dose of
3.43× 1014~e/cm-2. After radiation, the forward
currents of the SBDs at 2~V decreased by about 50%, and the
reverse currents at -200~V increased by less than 30%. Schottky
barrier height (φ B ) of the Ni/4H-SiC SBD increased
from 1.20~eV to 1.21~eV under 0~V irradiation bias, and decreased
from 1.25~eV to 1.19~eV under -30~V irradiation bias. The
degradation of φ B could be explained by the variation
of interface states of Schottky contacts. The on-state resistance
(Rs) and the reverse current increased with the dose, which
can be ascribed to the radiation defects in bulk material. The
specific contact resistance (\rhoc) of the Ni/SiC Ohmic
contact increased from 5.11× 105~Ωega.cm2 to 2.97× 10-4~Ωega.cm2. 相似文献
19.
Noninvasive temperature estimation by detecting echo-strain change including thermal expansion 下载免费PDF全文
This article studies the feasibility of noninvasive temperature estimation
by detecting echo-strain including thermal expansion in therapeutic
ultrasound treatment. This technique evaluates distributions of echo-strain
and temperature inside the tissue by detecting echo signals pre- and
post-heating, in combination with the temperature dependence of sound speed
and thermal expansion. In the computer simulation and experimental study,
echo signals pre- and post-heating are acquired and then the temperature
elevation is evaluated by correlation analysis. Results demonstrate that
this technique can effectively extend the measured temperature range up to
75$^{\circ}$C with an accuracy of $\pm $2$\,^{\circ}$C. 相似文献
20.
This paper reports that indium tin oxide (ITO) crystalline powders are prepared by coprecipitation method. Fabrication conditions mainly as sintering temperature and Sn doping content are correlated with the phase, microstructure, infrared emissivity c and powder resistivity of indium tin oxides by means of x-ray diffraction, Fourier transform infrared, and transmission electron microscope. The optimum sintering temperature of 1350℃ and Sn doping content 6~8wt% are determined. The application of ITO in the military camouflage field is proposed. 相似文献