Microstructural parameters and optical constants of ZnTe thin films with various thicknesses
TL;DR: In this article, the structural characteristics of polycrystalline ZnTe films have been studied by X-ray diffraction (XRD) and it was observed that the refractive index, n increased upon increasing the film thickness up to 508nm, lying within the experimental error for further increases in film thickness.
Abstract: Different thickness of polycrystalline ZnTe films have been deposited onto glass substrates at room temperature by vacuum evaporation technique. The structural characteristics studied by X-ray diffraction (XRD) showed that the films are polycrystalline and have a zinc blende (cubic) structure. The calculated microstructure parameters revealed that the crystallite size increases and microstrain decreases with increasing film thickness. The transmittance and reflectance have been measured at normal and near normal incidence, respectively, in the spectral range 400–2500 nm. For ZnTe films of different thicknesses, the dependence of absorption coefficient, α on the photon energy showed the occurrence of a direct transition with band gap energy E g opt = 2.21 ± 0.01 eV (For ZnTe films of different thicknesses) confirming the independency of deduced energy gap on film thickness. The refractive indices have been evaluated in terms of envelope method, which has been suggested by Swanepoul in the transparent region. The refractive index could be extrapolated by Cauchy dispersion relationship over the whole spectra range, which extended from 400 to 2500 nm. It was observed that the refractive index, n increased upon increasing the film thickness up to 508 nm, lying within the experimental error for further increases in film thickness.
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TL;DR: In this paper, the structural, optical and morphological properties of polycrystalline cupric oxide (CuO) thin films are studied and the bath temperature effects on the structural and optical properties of copper oxide films are investigated.
82 citations
TL;DR: In this paper, the dispersion of refractive index has been analyzed in terms of the Wemple-DiDomenico (WDD) single-oscillator model for different compositions of Co-doped zinc oxide.
Abstract: Different compositions of Co-doped zinc oxide [(Zn(1−x)Co
x
O) (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10)] thin films were evaporated onto highly clean glass substrates by thermal evaporation technique using a modified source. The structural properties investigated by X-ray diffraction revealed hexagonal wurtzite ZnO-type structure. The crystallite size of the films was found to decrease with increasing Co content. The optical characterization of the films has been carried out using spectral transmittance and reflectance obtained in the wavelength range from 300 to 2500 nm. The refractive index has been found to increase with increasing Co content. It was further found that optical energy gap decreases from 3.28 to 3.03 eV with increasing Co content from x = 0 to x = 0.10, respectively. The dispersion of refractive index has been analyzed in terms of Wemple–DiDomenico (WDD) single-oscillator model. The oscillator parameters, the single-oscillator energy (E
o), the dispersion energy (E
d), and the static refractive index (n
0), were determined. The nonlinear refractive index of the Zn(1−x)Co
x
O thin films was calculated and revealed well correlation with the linear refractive index and WDD parameters which in turn depend on the density and molar volume of the system.
59 citations
TL;DR: In this article, the optical constants (n, k ) and film thicknesses of ZnSe thin films were obtained by fitting the ellipsometric parameters ( ψ and Δ ) data using three layer model systems in the wavelength range 300-1100nm.
48 citations
TL;DR: In this paper, the electrical and optical properties of indium tin oxide (ITO) films with different thicknesses were measured by the standard four-point probe method, showing that the measured electrical properties refer to a decrease in the sheet resistance Rs (Ω/sq) with the increase in the annealing temperature.
40 citations
TL;DR: In this article, an optical characterization method based on Swanepoel's ideas (envelope method) has been employed to extract the refractive index n and film thickness d, with accuracies better than 1%.
Abstract: Optical properties of amorphous Se80 − xTe20Bix thin films with different compositions (x = 0, 2, 4, 6 and 8 at.%) deposited by evaporation technique have been investigated by optical spectrophotometry measurements in the wavelength range of 400–2500 nm. An optical characterization method for uniform films based on Swanepoel's ideas (envelope method) has been employed to extract the refractive index n and film thickness d, with accuracies better than 1%. It was found that the refractive index increases with increasing the concentration of Bi at the expense of Se content. The increasing in refractive index n is interpreted in terms of polarizability and the mean coordination number. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple–DiDomenico model. The fundamental parameters for the investigated semiconducting thin films Se80 − xTe20Bix e.g. absorption coefficient and band gap are calculated in the strong absorption region of transmittance and reflectance spectra. The possible optical transition in these films is found to be allowed indirect transition with energy gap Egoptdecreases from 1.467 to 1.035 eV with increasing Bi content at expense of Se. Finally, the decrease in the optical band gap with increasing Bi content in Se80 − xTe20Bix has been explained in terms of the chemical bond approach.
39 citations
References
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TL;DR: In this paper, the authors used a Geiger counter spectrometer to measure the changes in intensity distribution in the spectra of cold worked aluminium and wolfram and found that the line breadths may be attributed to simultaneous small particle size and strain broadening, the latter predominating at the higher Bragg angles.
7,802 citations
Book•
01 Jan 1954
6,295 citations
"Microstructural parameters and opti..." refers background or methods in this paper
...In the present work, the instrumental broadening-corrected ‘‘pure’’ FWHM of each reflection was calculated from the parabolic approximation correction [14]:...
[...]
...Each X-ray diffraction line profile is broadened due to instrumental and physical factors (crystallite size and lattice strains) [14]....
[...]
...Therefore, the first indispensable preparatory step to the calculation of crystallite size and lattice strain from the recorded XRD scan is the determination of the ‘‘pure’’ diffraction line profile for a given reflection whose full-width at half maximum (FWHM) depends solely on the physical factors [14]....
[...]
...Simple equations or graphs based on line profiles of assumed analytical forms can be used for the instrumental broadening correction [14]....
[...]
...The method was based on the assumption that the crystallite size and strain line profiles are both presumed to be Cauchy and the appropriate equation for the separation of crystallite size (Dv) and microstrain (e) takes the following form [14]:...
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Book•
01 Jan 1971TL;DR: Optical processes in semiconductors as mentioned in this paper, Optical Process in Semiconductors (OPP), Optical Process of Semiconductor (OPS) and Optical Process (OPI)
Abstract: Optical processes in semiconductors , Optical processes in semiconductors , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
4,630 citations
"Microstructural parameters and opti..." refers background in this paper
...where K is a characteristic parameter (independent of photon energy) for respective transitions [25], hn denotes to photon energy, E g is optical energy gap and m is a number which characterizes the transition process....
[...]
TL;DR: In this article, a rigorous expression for the transmission of a thin absorbing film on a transparent substrate is manipulated to yield formulae in closed form for the refractive index and absorption coefficient.
Abstract: The rigorous expression for the transmission of a thin absorbing film on a transparent substrate is manipulated to yield formulae in closed form for the refractive index and absorption coefficient. A procedure is presented to calculate the thickness to an accuracy of better than 1% with similar accuracies in the values of n. A method to correct for errors due to slit width is also given. Various formulae to calculate the absorption coefficient accurately over almost three orders of magnitude are discussed. Only data from the transmission spectrum are used and the procedure is simple, fast and very accurate. All formulae are in closed form and can be used on a programmable pocket calculator.
3,482 citations
TL;DR: In this article, the experimental evidence concerning the density of states in amorphous semiconductors and the ranges of energy in which states are localized is reviewed; this includes d.c and a.c. conductivity, drift mobility and optical absorption.
Abstract: The experimental evidence concerning the density of states in amorphous semiconductors and the ranges of energy in which states are localized is reviewed; this includes d.c. and a.c. conductivity, drift mobility and optical absorption. There is evidence that for some chalcogenide semiconductors the model proposed by Cohen, Fritzsche and Ovshinsky (1969) should be modified by introducing a band of localized states, near the centre of the gap. The values of C, when the d.c. conductivity is expressed as C exp (- E/kT), are considered. The behaviour of the optical absorption coefficient near the absorption edge and its relation to exciton formation are discussed. Finally, an interpretation of some results on photoconductivity is offered.
3,465 citations