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1.
We grew modulated BeZnO layers by hybrid plasma-assisted molecular-beam epitaxy/electron-beam deposition. A wide band-gap
investigation of the modulated Be
x
Zn 1−x
O by means of photocurrent (PC) spectroscopy was conducted. The band-gap energy was directly acquired from the wavelength
of the PC peak, caused by the band-to-band transition. By increasing x, which was the rate of the Be elements, the optical band-gap energy was empirically fitted by E
BeZnO( x) = 6.32( x–1) x + 7.305 x + 3.295. We expect that this finding can open new possibilities for wide band-gap engineering of BeZnO layers, which can
be utilized as barrier layers in active layers consisting of ZnO/BeZnO quantum well structures and solar-blind ultraviolet
photodetectors. 相似文献
2.
Cd 1−xZn xTe (where x = 0.02, 0.04, 0.06, 0.08) thin film have been deposited on glass substrate at room temperature by thermal evaporation
technique in a vacuum at 2 × 10 −5 torr. The structural analysis of the films has been investigated using X-ray diffraction technique. The scanning electron
microscopy has been employed to know the morphology behaviour of the thin films. The temperature dependence of DC electrical
conductivity has been studied. In low temperature range the thermal activation energy corresponding to the grain boundary—limited
conduction are found to be in the range of 38–48 μeV, but in the high temperature range the activation energy varies between
86 and 1.01 meV. The built in voltage, the width of the depletion region and the operating conduction mechanism have been
determined from dark current voltage (I–V) and capacitor-voltage (C–V) characteristics of Cd 1−xZn xTe thin films. 相似文献
3.
The proton conductivity of barium-yttrium hydrocuprate H xYBa 2Cu 3O 7+y ( x≤2,−0.1≤ y≤0.1) was determined for the first time. The proton conductivity (10 −6 S cm −1 at 470 K, with an activation energy of −0.6 eV) accounts for 0.1% of the total dc conductivity. Owing to the proton conductivity of strontium cerate (H zSrCe 0.9Y 0.1O 3, z<0.1) and hydrocuprate layers in the Pd/cerate/hydrocuprate/cerate/Pd sandwich structure, this heterogeneous system exhibits the properties of an electric accumulator with emf=0.6–1.2 V. 相似文献
4.
In this paper, the mechanism of Hg 1−xCd xTe/Si heterojunction grown by HWE (Hot Well Epitaxy) was studied. Opitical characterizations were shown with FTIR, the composition
x = 0.39 was deduced by using MIR transmittance, the absorbing peak at 319.4 cm −1 was measured by FIR transmittance, 319.4 cm −1 confirmed the existence of Si–Te bond of at Si/HgCdTe interfacial layer. The I-V characteristics at both room temperature
and 77 K of HgCdTe ( n-type)/Si ( p-type) heterojunction show that the good p-n heterojunction properties was obtained by using HWE. XRD study confirmed the
formation of (111) oriented HgCdTe on (211) Si. Morphology of a cross section observed using EPMA indicates the columnar growth
of HgCdTe. An analysis of interfcial layer by EPMA indicated presence of three layers composed of Si + Te, Si + Te + Hg and
Si + Te + Cd + Hg. Among them, the most important one is the first layer. The problem of lattice mismatch and the difference
of thermal expansion coefficient between Si and CdTe or HgTe may be improved by formation of Si–Te stable chemical bond through
bybridization orbital bonding between Si and Te. The second and third layers are formed by evaporation-interdiffusion. Formation
of the whole interfacial layer provides the appetency for the growth of (111) Hg 1−xCd xTe epilayer on (211) Si substrate. 相似文献
5.
High purity layers of In 1 −x
Ga
x
As have been grown by liquid phase epitaxy using a novel impurity gettering technique with rare earth atoms. The electron
concentration could thus be decreased from 3 × 10 18 cm −3 to 2·4 × 10 15 cm −3 and the mobility increased from 7 110 cm 2/Vs to 18,981 cm 2/Vs (100 K). The excellent quality of the layers has been evidenced by X-ray diffraction and photoluminescence measurements.
The fabrication of p-i-n photodiodes using this technique is described and reliability aspects addressed. 相似文献
6.
Cd 1−xZn xS/CuInSe 2 solar cells having efficiencies in the range of 2·3% were fabricated by spray pyrolysis. The best cell had the following
parameters: V
oc = 305 mV, J
sc = 32 mA/cm 2, FF = 0·32 area = 0·4 cm 2 and efficiency = 3·149%. V
oc versus temperature measurements showed that the electron affinity difference was 0·22 eV. Forward dark current versus voltage
curves were plotted and a possible current mechanism occurring in these cells has been proposed. 相似文献
7.
Deep surface states are discovered on the interface between 6H-SiC and its native thermal oxide by analyzing the C-V characteristics of metal-oxide-semiconductor structures measured at a high temperature (600 K). The maximum of the density
of states distributed according to energy ( D
tm=2×10 12 cm −2· eV −1) is at an energy about 1.2 eV below the bottom of the conduction band of SiC. It is postulated that the states discovered
are similar in nature to the P
b centers observed in the SiO 2/Si system.
Pis’ma Zh. Tekh. Fiz. 23, 55–60 (October 26, 1997) 相似文献
8.
The crystal and electronic structures, as well as the luminescence properties of Sr 2Al 2–xSi 1+xO 7–xN x:Eu 2+ are reported. First-principles calculations energetically confirm that the Al and Si atoms are in partial ordering in the 2a and 4e sites in Sr 2Al 2SiO 7. In addition, the band structure calculation shows that Sr 2Al 2SiO 7 has an indirect band gap with an energy gap of about 4.07 eV, which is in good agreement with the experimental data (~5.3 eV) obtained from the diffuse reflection spectrum. The crystal structure of Sr 2Al 2SiO 7 can be modified by Si–N substitution for Al–O in the lattice with a maximum solubility of about x ¼ 0.6. The average bond length of Eu Sr–(O,N) slightly increases although the lattice parameters decrease with the incorporation of Si–N in Sr 2Al 2SiO 7:Eu 2+. Under excitation in the visible spectral region, Sr 2Al 2–xSi 1+xO 7–xN x:Eu 2+ emits blue to yellow light with a broad emission band in the range of 480–570 nm, varying with both the Eu concentration and the x value. The red shift of the emission band of Eu 2+ is associated with an increase in the crystal-field splitting and the covalency, which arise from the incorporation of nitrogen as well as the energy transfer between the Eu ions at high Eu concentrations. Moreover, the Eu ions have a strong effect on both the concentration quenching and the thermal quenching in Sr 2Al 2–xSi 1+xO 7–xN x. The temperature dependence of photoluminescence indicates that Sr 2Al 2–xSi 1+xO 7–xN x:Eu 2+ shows strong thermal quenching due to the dominant nonradiative process at room temperature. 相似文献
9.
The temperature-dependent lifetime of trivalent cerium was determined in (Y 1−x
Ce
x
) 3Al 2.5Ga 2.5O 12 (where x = 0.1 and 0.2) over a temperature range of 20−120 °C. In both samples, the quenching temperature is significantly lower compared
to (Y 1−x
Ce
x
) 3Al 5O 12. The difference in quenching temperatures is explained by evaluating the changes in the lattice, which occur as a result
of substituting the Al 3+ for Ga 3+. The information presented in this report is useful for future design of phosphors for use as non-contact temperature sensors. 相似文献
10.
A low thermal-expansion material was synthesized with potential application in thermal-shock-resistant infrared-transmitting windows. The material is derived from a solid solution of Al 2(WO 4) 3, which has positive thermal expansion, and Sc 2(WO 4) 3 with a negative thermal expansion. An optimum composition of Al 0.5Sc 1.5(WO 4) 3 was identified by synthesizing solid solutions, Al 2−x Sc x (WO 4) 3, by a solid-state route with compositions ranging from x = 0 to 2.0. A single orthorhombic phase was obtained at all compositions. A composition corresponding to x = 1.5 had a low coefficient of thermal expansion of −0.15 × 10 −6/°C in the temperature range 25–700 °C. A low temperature solution combustion process was developed for this optimum composition, resulting in a single-phase powder with a surface area of ~14 m 2/g and average particle size (as determined from surface area) of 92 nm. The powder was consolidated by slip-casting, sintering, and hot-isostatic pressing into visibly translucent disks with a peak in-line transmittance of 73 % at 2300 cm −1. Significant infrared absorption in a 1-mm-thick disk of this material begins near 2200 cm −1 and features three absorptions arising from 2-phonon transitions at 2002, 1847, and 1676 cm −1. The infrared and Raman spectra are interpreted in terms of 1-, 2-, and 3-phonon vibrational transitions. 相似文献
11.
Series of glass based on the (80 − x)TeO 2–20ZnO–( x)Er 2O 3 system (0.5 mol% ≤ x ≤ 2.5 mol%) has successfully been made by melt quenching technique. The optical properties of glass have been investigated
by means of IR and Raman spectroscopy. It is observed that as the Er 2O 3 content is being increased, the sharp IR absorption peaks are consistently shifted from 650 to 672 cm −1 while the Raman shift intensity around 640–670 cm −1 is decreases but increases around 720–740 cm −1. It is found out that both phenomenons are related to the structural changes between the stretching vibration mode of TeO 4 tbp and TeO 3 tp, and bending vibration mode of Te–O bonds in the glass linkages. 相似文献
12.
We have measured the high energy crystalline electric field transitions in samples of Pr
x
Y 1−x
Ba 2Cu 3O 7−δ with x ≈ 0·5 and x ≈ 1. The fully Pr-doped samples exhibits three strong transitions with excitation energies of about 65, 85 and 105 meV, plus
three more weaker ones at 113, 123 and 132meV. Magnetic intensity is observed in the same energy range in the x=0.5 sample but is largely structureless in character, with only one clear peak at about 109meV. The large number of transitions
would seem to indicate a Pr valence of 3+, rather than 4+, but the intrinsically broad character of the excitations is evidence
for a dynamically mixed valence state. 相似文献
13.
Here, we fabricated In2O3(ZnO)m (IZO) superlattice microplates with hexagon morphologies by the substrate-free optical vapor supersaturated precipitation. The IZO microplates possessed a superlattice structure with a large m number, i.e., m?=?23, consisting of layered alternating stacks of octahedral InO2? as inversion boundaries and layered InZnmOm+1+ as a zig-zag modulated pattern. The Raman peak at 613 cm?1 confirmed the superlattice of the IZO microplates. The broad asymmetric excitonic photoluminescence (PL) emission with the photon energy of 3.236 eV indicated the heavy doping of indium in the IZO, resulting a redshift of?~?32 meV from the near-band-edge emission. The unusual negative thermal quenching of PL intensity was also observed. Moreover, the anisotropic electrical properties of the IZO superlattice microplates were manifested, for the first time, where the in-plane conductivity was two orders of magnitude higher than out-plane one. The present work provided new insight into the free-standing IZO superlattice microdevices for future optoelectronic applications. 相似文献
14.
A modified chemical deposition process is employed for the preparation of thin-film (CdS)
x
-(PbS) 1 −x
composites with 0·2 ≤ x ≤ 0·8. Cadmium sulphate, lead acetate and thiourea are used as the basic source materials. The electrical conductivity is
found to decrease with increasing composition parameter x up to 0·5 and increase for further increase in x. The composites are polycrystalline as is revealed from XRD and microscopic observations and show phases of both cubic and
hexagonal CdS, cubic CdO and PbS, and tetragonal PbO and PbO 2. Additional peaks of free elemental Cd and S have also been observed. For all the phases no significant variation in lattice
parameters with x has been observed. The optical absorption studies show the presence of four well-defined absorption edges at approximately
0·45 eV, 1·05eV, 1·80 eV and 2·35 eV, at the same energies for all x values. The absorption coefficient is of the order of 10 4 cm −1 and mode of band-to-band transition is of the direct type. 相似文献
15.
Transparent ZnO thin film transistors (ZnO–TFTs) with different structures and dielectric layers were fabricated by rf magnetron
sputtering. The PbTiO 3, AlO
x
, SiN
x
and SiO
x
films were attempted to serve as the gate dielectric layers in the devices, respectively, and XRD was employed to investigate
the crystal structure of ZnO films deposited on these dielectric layers. The optical properties of transparent TFTs were measured
and revealed the average transmittance ranged from 60 to 80% in the visible part of the spectrum. Electrical measurement shows
the properties of the ZnO–TFTs have great relations with the device structure. The bottom-gate TFTs have better behaviors
than top-gate ones with the mobility, threshold voltage and the current on/off ratio of 18.4 cm 2 V −1 s −1, −0.7 V and 10 4, respectively. The electrical difference of the devices may be due to different character of the interface between the channel
and dielectric layers. 相似文献
16.
New NASICON type materials of composition, Li 3−2x
Al 2−x
Sb
x
(PO 4) 3 ( x = 0·6 to 1·4), have been prepared and characterized by powder XRD and IR. D.C. conductivities were measured in the temperature
range 300–573 K by a two-probe method. Impedance studies were carried out in the frequency region 10 2−10 6 Hz as a function of temperature (300–573 K). An Arrhenius behaviour is observed for all compositions by d.c. conductivity
and the Cole-Cole plots obtained from impedance data do not show any spikes on the lower frequency side indicating negligible
electrode effects. A maximum conductivity of 4·5 × 10 −6 S cm −1 at 573 K was obtained for x = 0·8 of the Li 3−2x
Al 2−x
Sb
x
(PO 4) 3 system. 相似文献
17.
The diffusion of samarium in polycrystalline samarium sulfide with a superstoichiometric composition of Sm 1.13S has been studied at T = 1000 and 1100°C. It is concluded that Sm atoms predominantly migrate over the boundaries of monocrystalline domains of
the polycrystalline sample. The diffusion coefficient varies within D ≈ 10 −2−10 −3 cm 2/s. In the temperature dependence of the diffusion coefficient, the diffusion activation energy is evaluated at E ∼ 4.6 eV and the preexponential term at D
0 ≈ 1.8 × 10 15 cm 2/s. 相似文献
18.
Photoluminescence (PL) properties of Ammonium Silicon Fluoride samples prepared by vapour etching technique are investigated with respect to excitation energy, excitation intensity and temperature. Ageing effect at ambient conditions is also examined by Fourier Transform Infrared Spectroscopy. PL peak maximum blue shifts as the excitation intensity increases and saturates at 2.106 eV. Temperature-dependent variations in PL peak energies and intensities cannot be thoroughly elucidated via Quantum Confinement model alone and require consideration of recombination rates at Si–SiO x interface. Temperature dependence of integrated PL intensity is treated by a three-component functional form.Infrared absorption bands at 1060 cm − 1, 1113 cm − 1 and 1230 cm − 1 attain saturation with time. Agreement between the saturation time of SiO x longitudinal optic mode at 1230 cm − 1 and that deduced from PL measurements in literature is noted. It is shown that PL emissions are intrinsic in nature and have a significant excitonic contribution. 相似文献
19.
It is found that the hysteresis that develops with decreasing temperature in the current-voltage characteristics of thin-film
YBa 2Cu 3O 7−x
microbridges is due to superheating of the bridges by the transport current. The heat transport coefficient is determined
to be α=5500–7500 V/(cm 2·K) and the thermal resistance of the YBa 2Cu 3O 7−x
/MgO film-substrate interface is R
if=(1.3–1.8)×10 −4 (cm 2·K)/W.
Pis’ma Zh. Tekh. Fiz. 23, 56–62 (June 26, 1997) 相似文献
20.
Gallium indium phosphide (Ga
x
In 1−x
P) epitaxial layers were grown on GaAs substrates by chemical beam epitaxy (CBE) without thermally precracking the group V precursor. Trisdimethylaminophosphine (TDMAP), triisopropylgallium (TIPGa), and ethyldimethylindium (EDMIn) were used as the phosphorus, gallium and indium sources, respectively. Ga
x
In 1−x
P was grown without group V precracking for substrate temperatures in the range of 400–520 °C. Above 500 °C, the epilayers had a hazy appearance presumably due to being phosphorus deficit. A strong solid composition dependence on substrate temperature was observed. The samples were In-rich at low growth temperatures and Ga-rich at high growth temperatures. It was possible to grow the Ga
x
In 1−x
P epilayers over a large composition range with good morphology and strong photoluminescence. Values of full width at half maximum were as low as 45 meV at 14 K photoluminescence measurements. 相似文献
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