共查询到20条相似文献,搜索用时 15 毫秒
1.
Thin films of amorphous Se100−xSbx (x=5,10 and 20 at%) system are deposited on a silicon substrate at room temperature (300 K) by thermal evaporation technique. The optical constant such as refractive index (n) has been determined by a method based on the envelope curves of the optical transmission spectrum at normal incidence by a Swanpoel method. The oscillator energy (Eo), dispersion energy (Ed) and other parameters have been determined by the Wemple–DiDomenico method. The absorption coefficient (α) has been determined from the reflectivity and transmitivity spectrum in the range 300–2500 nm. The optical-absorption data indicate that the absorption mechanism is a non-direct transition. We found that the optical band gap, Egopt, decreases from 1.66±0.01 to 1.35±0.01 eV with increase Sb content. 相似文献
2.
Qian Dingrong Tang Wenguo Shen Jie Chu Junhao Zheng Guozhen 《Solid State Communications》1985,56(9):813-816
The infrared absorption spectra, including absorption edge spectra and below-gap absorption spectra, were investigated both experimentally and theoretically for an In-doped degenerate HgCdTe sample with an electron concentration Ne = 7.0 × 1017 cm-3 for wavelengths 7 μm<L<17 μm at the temperatures 77 K <T< 300 K. The possibility of applying free-carrier absorption theory developed for InSb to HgCdTe is discussed. It is concluded that the virtual crystal approximation works fairly well for HgCdTe and that the two-mode Callen effective charge should be used in the calculation of free-carrier absorption coefficients to account for the two-mode character of the optical phonons of HgCdTe. Good agreement between theory and experiment in the below-gap absorption spectra was obtained. The concentration of ionized impurities was found to be Nimp=3.4 × 1018 cm-3. A good account of the behaviour of absorption edge in the light of Burstein-Moss effect has also been given. 相似文献
3.
N.M. Gasanly 《Physica B: Condensed Matter》2012,407(21):4318-4322
The absorption edge of undoped Tl2Ga2S3Se crystals have been studied through transmission and reflection measurements in the wavelength range 440–1100 nm and in the temperature range 10–300 K. The absorption edge was observed to shift toward lower energy values with increasing temperature. As a result, the rate of the indirect band gap variation with temperature γ=−2.6×10−4 eV/K and the absolute zero value of the band gap energy Egi(0)=2.42 eV were obtained. 相似文献
4.
I. V. Bodnar’ S. A. Pavlyukovets A. V. Danilchik E. V. Lutsenko 《Journal of Applied Spectroscopy》2011,78(5):755-758
We have used the Bridgman method to grow single crystals of the ternary compound FeIn2Se4 and we have determined their composition and structure. We measured the transmission spectra in the intrinsic absorption
edge region in the temperature range 20–300 K. From the transmission spectra, we determined the bandgap width and plotted
its temperature dependence. We show that the Eg(T) dependence has a shape typical for semiconductor compounds. 相似文献
5.
D. Auvergne J. Camassel H. Mathieu A. Joullie 《Journal of Physics and Chemistry of Solids》1974,35(2):133-140
Piezoreflective experiments between 77 and 300°K are performed on Gax, In1?x Sb alloys. Eo and Eo + Δo transition energies, vs composition are determined. Band gap Eo variations, are obtained in good agreement with the two band dielectric model. The Δo splitting is observed to be linear with composition.The fundamental edge temperature coefficient β is also determined, it is found to vary linearly with composition.Eo and Eo + Δo energy determination permit one to deduce effective mass and ge value variation with composition. 相似文献
6.
《Infrared physics》1990,30(6):505-511
Photosensitive monocrystalline films Pb1 − xCdxSe (x⩽ 0.03) of low carrier concentration (n = 0.3 ÷ 4 × 1017 cm−3 have been grown by hot wall epitaxy method on cleaved (111)BaF2 or (100)KCl substrates.Photoconductive thresholds determined by spectral response measurements (at temperatures 4.2, 77 and 300 K) were in good agreement with the fundamental absorption edges and showed a large increase in the energy gap Eg with Cd content. Photoconductivity in the impurity range (hv < Eg) was observed.The temperature dependence of the Hall coefficient and the mobility between 4.2 and 300 K have been studied. Temperature freeze out of the free carriers was observed.Discussion of the carrier scattering mechanisms and impurity photoconductivity phenomena is presented. 相似文献
7.
Katerina Kotkova Helena Ticha Ladislav Tichy 《Journal of Raman spectroscopy : JRS》2008,39(9):1219-1226
Five (PbO)x(Bi2O3)0.2(B2O3)0.8−x glasses, where x = 0, 0.2, 0.3, 0.4 and 0.6, were prepared. The dilatometric glass transition temperature (Tg) was found in the region 470 (x = 0)≥ Tg ( °C) ≥ 347 (x = 0.6), and the density (ρ) varied within 4.57 (x = 0) ≤ ρ (g/cm3) ≤ 8.31 (x = 0.6). Raman spectra indicated the conversion of BO3 to BO4 entities for low x values but for x > 0.3, namely, for x → 0.6, back‐conversion occurred, most probably. From the measurements of the optical transmission on very thin bulk samples, the room temperature optical gap values (Eg) were determined to be in the range 4.03 (x = 0)≥ Eg (eV) ≥ 3.08 (x = 0.6). The temperature (T) dependence of the optical gap (Eg(T)) in the region 300 ≤ T(K) ≤ 600 was examined and approximated by a linear relationship of the form of Eg(T) = Eg(0)− γT, where γ × 10−4(eV/K) varied from 5.1 to 6.8. The non‐linear refractive index (n2) was estimated from the optical gap values and it was found to correspond to the n2 values calculated from the experimental third‐order non‐linear optical susceptibility taken from the literature. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
8.
The temperature dependence of the fundamental absorption edge in CuGaSe2 single crystals was determined in the temperature range from 15 to 300 K. Above about 120 K the gap energy changes linearly with temperature with dEg/dT = ? (2.1 ± 0.1) eV K?1. The downshift in dEg/dT of the I–III–VI2 compounds compared to their II–VI analogs is discussed accounting for the p-d hybridization of the uppermost valence band. 相似文献
9.
Optical transmittance measurements near the absorption edge of [Kx(NH4)1−x]2ZnCl4 mixed crystals, where x=0.00, 0.232, 0.522, 0.644, 0.859 and 1.00, are reported over 276–350 K range. Analysis reveals that the type of transition is the indirect allowed one. The absorption edge shifted towards lower energy with increasing temperature. It is shown that [Kx(NH4)1−x]2ZnCl4 mixed crystals with x0.644 reveal a phase transition at 319 K, this phase disappeared at high concentrations of K+ ions. The steepness parameter is given, its value is used to estimate the temperature dependence of the indirect energy gap. In the region of the absorption edge, the absorption coefficient obeys Urbach's rule. Urbach parameters are investigated as a function of temperature. 相似文献
10.
A.S SoltanA.A Abu-Sehly M.A Abdel-Rahim 《Journal of Physics and Chemistry of Solids》2002,63(5):801-809
The optical absorption of the as-prepared and thermally annealed Se85−xTe15Sbx (0≤x≤9) thin films was measured. The mechanism of the optical absorption follows the rule of non-direct transition. The optical energy gap (E0) decreased from 1.12 to 0.84 eV with increasing Sb content of the as-prepared films from 0 to 9 at.%. The as-prepared Se76Te15Sb9 films showed an increase in (E0) with increasing the temperature of annealing in the range above Tg (363 K). The electrical conductivity of the as-prepared and annealed films was found to be of Arrhenius type with temperature in the range 300-360 K. The activation energy for conduction was found to decrease with increasing both the Sb content and temperature of annealing. The results were discussed on the basis of the lone-pair electron effect and of amorphous crystalline transformation. 相似文献
11.
12.
E. A. Popov 《Russian Physics Journal》2003,46(10):962-968
Results of experimental investigations into the optical absorption spectrum of Rb2MnxCd1–x
Cl4 solid solutions corresponding to 6
A
1g
4
A
1g
4
E
g transitions in manganese ions are presented. The spectra were measured at variable temperatures, magnetic fields, and concentrations x. The magnetic phase transitions accompanying variations of these parameters cause considerable changes in the spectrum. The exciton and exciton-magnon bands, their cold and hot magnon analogs, and the phonon satellite bands have been detected. The specific features of the optical absorption spectrum caused by the low-dimensional magnetic order are elucidated. 相似文献
13.
Barbara Sujak-Cyrul Bogumil Kolodka Jan Misiewicz Janusz M. Pawlikowski 《Journal of Physics and Chemistry of Solids》1982,43(11):1045-1051
Absorption measurements were made on single crystals and thin films of Zn3As2; within the photon energy range of 0.12–1.16 eV at temperatures of 300, 80 and 5 K and reflectivity was measured in the range of 1.0–5.5 eV at 300 K. Absorption below the fundamental edge has been interpreted as a process involving three mechanisms: (i) free-carrier absorption, (ii) intraband transitions between levels in the valence band, and (iii) direct transitions from valence levels to the acceptor level/band. The fundamental absorption edge has been ascribed to direct interband transitions from three valence levels to one conduction level. An isotropic three-level Kane band model has been used to interpret the experimental data, modified by introducing the light-hole level split from the heavy-hole level due to the tetragonal crystal field. A reasonable fit of the model to the experimental results has been obtained in the region of both intraband and interband absorption for the following set of parameters: Eg = 0.985 eV, ΔSO = 0.30 eV, ΔCF = 0.05 eV, m*hh = 0.36 m0 and P = 4 × 10?10eVm (at 300 K). A proposed Zn3As2 energy-band model near the Γ point is described to interpret the observed absorption. 相似文献
14.
Amorphous alloys of Si and Ge have been prepared over the entire composition range by r.f. plasma decomposition of mixed gases of SiH4 and GeH4. The optical absorption edge is found to have a linear dependence on alloy composition given by: Eg = 0.95 + 0.70x (eV). 相似文献
15.
I. Balslev 《Solid State Communications》1980,35(10):771-773
A spectroscopic determination of the energy gap Eg and the exciton energy Ex in highly excited Ge at T = 5–20K is presented. Within 0.05 meV we observe no shift of Eg and Ex up to electron-hole densities of 1014?1015 cm?3. In this range all previous theories predict a sizeable band renormalization (ΔEg ≈?0.3 meV to ? 2 meV). 相似文献
16.
D. I. Bletskan V. N. Kabacij I. P. Studenyak V. V. Frolova 《Optics and Spectroscopy》2007,103(5):772-776
Edge absorption spectra of crystalline and glassy lead thiogermanate (PbGeS3) have been measured in the temperature range from 77 to 470 K. It is shown that the dependence of the absorption coefficient on the photon energy for the glassy and crystalline states in the polarization E ∥ c is described by the Urbach rule. For the crystal in the polarization E ∥ b, at T < 300 K, an almost parallel shift of the intrinsic absorption edge to lower energies occurs with an increase in temperature, whereas at T ≥ 300 K, the Urbach absorption edge is observed. The parameter σ0, related to the electron-phonon coupling constant, and the energy ?ωph of the effective phonons involved in the formation of the absorption edge of crystalline PbGeS3 are determined from the temperature dependence of the parameter of the absorption edge slope. The contributions of the dynamic and static disorders to the diffusion of the absorption edge of crystalline PbGeS3, as well as the topological disorder of glassy PbGeS3, have been estimated. 相似文献
17.
介绍了利用电子束蒸发技术在蓝宝石光纤端面上生长具有良好表面形貌和晶体结构的ZnO薄膜方法.不同测试温度(室温至773 K)条件下的透射光谱显示,蒸镀在蓝宝石光纤端面上的ZnO薄膜,其光学吸收边随温度升高而发生红移现象,且禁带宽度和热力学温度之间满足Eg(T)=340-491×10-4T的关系.这为今后进一步利用ZnO薄膜的禁带宽度检测相应的环境温度,研制以ZnO薄膜为敏感材料的新型宽量程光纤温度传感器打下了良好的基础.
关键词:
ZnO薄膜
蓝宝石光纤
光学吸收边
光纤温度传感器 相似文献
18.
Magnetic and kinetic properties as well as transmission and absorption spectra of Hg
1−x−y
Mn
x
Fe
ySe (0.09 ≤ x ≤ 0.099 and 0.001 ≤ y ≤ 0.01) crystals are investigated at H ≈ 0.5–6 kOe in the temperature range T = 77–300
K. The band parameters are determined on the basis of experimental data. It is found that in the crystals under study at T
≈ 300 K, electron scattering by polar optical phonons dominates, direct optical band-to-band transitions occur, and replacement
of a part of Mn atoms by Fe for x + y = 0.1 results in an increase in Eg
op with Fe content.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 35–39, March, 2007. 相似文献
19.
I. V. Bodnar 《Journal of Applied Spectroscopy》2010,77(5):654-657
Single crystals of In2Se3 and CuIn5Se8 compounds and (In2Se3)1–x·(CuIn5Se8)x solid solutions have been grown from the melt using the Bridgman method and their composition and structure determined. It
is shown that the crystals have n-type conductivity. Their transmission spectra were studied in the self-absorption edge region
at 80 and 295 K. Based on the spectral measurements, the band gap width (Eg) was determined and the band gap concentration dependences were plotted. It is found that Eg varies with the x composition nonlinearly. Using the dielectric model of Van Vechten–Bergstresser and the Hill–Richardson
pseudo potential model, Eg(x) was calculated theoretically. 相似文献
20.
Cd1-x ZnxS nanocrystals are prepared by a co-precipitation method with different atomic fractions of Zn.The texture,structural transformation and optical properties with increasing x value in Cd1-x ZnxS are studied with scanning electron microscopy,electron diffraction patterning,and absorption spectra respectively.Quantum confinement in a strained CdS/Cd1-xZnxS related nanodot with various Zn content values is investigated theoretically.Binding energies on exciton bound CdS/CdxZn1-xS quantum dot are computed,with consideration of the internal electric field induced by the spontaneous and piezoelectric polarizations,and thereby the interband emission energy is calculated as a function of the dot radius.The optical band gap from the UV absorption spectrum is compared with the interband emission energy computed theoretically.Our results show that the average diameter of composite nanoparticles ranges from 3 nm to 6 nm.The X-ray diffraction pattern shows that all the peaks shift towards the higher diffracting angles with an increase in Zn content.The lattice constant gradually decreases as the Zn content increases.The strong absorption edge shifts towards the lower wavelength region and hence the band gap of the films increases as the Zn content increases.The values of the absorption edge are found to shift towards the shorter wave length region and hence the direct band gap energy varies from 2.5 eV for the CdS film and 3.5 eV for the ZnS film.Our numerical results are in good agreement with the experimental results. 相似文献