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1.
The effect of annealing on the structural and optical properties of thermally evaporated Ge30Se70 and Ge30Se60Bi10 thin films is reported in this paper. The prepared films were thermally annealed at 250°C to optimize the optical properties which can be used for the optical device fabrication. X-ray diffraction study revealed no structural transformation whereas the surface morphology changed as observed from scanning electron microscopy. The optical properties of the deposited and annealed films have been investigated by using a UV–VIS–NIR spectrophotometer in the wavelength range of 400–1100?nm. The optical band gap of the Ge30Se70 annealed film is found to be increased while the energy gap of the Bi-doped annealed Ge30Se60Bi10 thin film decreased which is explained by the chemical disorderness, defect states and density of localized states in the mobility gap. The Tauc parameter and Urbach energy which measure the degree of disorder changed with the annealing process. The transmittivity increases and the absorption power decreases in the Ge30Se70 annealed film, whereas the reverse effect is noticed for the annealed Ge30Se60Bi10 thin film. The irreversible nature of this change can be useful for optical recording purposes. 相似文献
2.
Structural and optical properties of Ge20SbxSe80-x films 总被引:1,自引:0,他引:1
A.H. Moharram 《Applied Physics A: Materials Science & Processing》1998,66(5):515-519
20 SbxSe80-x (where 10≤x≤40 at.%) thin films. The optical absorption results indicate that the absorption mechanism is due to non-direct
transition. The optical gap of the as-deposited films was found to decrease monotonically with increasing antimony content,
a result which was interpreted on the basis of the chemical-bond approach proposed by Bicerno and Ovshinsky. Annealing of
the Ge20Sb40Se40 films at temperatures higher than 450 K was found to decrease the optical gap and increase the refractive index of the investigated
film. Increasing the amount of crystalline GeSe2 and Sb2Se3 phases while increasing the annealing temperature could be responsible for the continuous decrease of the optical gap of
the Ge20Sb40Se40 film.
Received: 4 November 1997/Accepted: 16 December 1997 相似文献
3.
V. S. Bilanych S. S. Kikemezey I. M. Rizak V. M. Rizak 《Physics of the Solid State》2011,53(11):2316-2320
The mechanical properties of As2Se3 and Ge2Se3 thin films have been studied by the method of quasi-static nonoindentation. The mechanisms of formation and recovery of the
indentations in the studied materials have been analyzed under conditions of their local loading. It has been revealed that
the deformation mechanism of the chalcogenide films changes in going from As2Se3 to Ge2Se3. It has been found that, during deformation of the As2Se3 film under the indenter, the accumulation of plastic deformation prevails, and, for the Ge2Se3 film, the substantial mechanism is the relaxation of its deformation. 相似文献
4.
Reversible photo-induced volume changes have been observed accompanying reversible optical absorption edge shift produced by successive cycles of band gap illumination and annealing for well-annealed evaporated As2S3 and As4Se5Ge1 films. The As2S3 film shows an increase in its volume by illumination, while As4Se5Ge1 film shows a decrease. Qualitative discussion has been given in connection with pressure-induced optical constant change. 相似文献
5.
This paper reports the effect of replacement of selenium by antimony on the optical gap and some other physical parameters of new quaternary chalcogenide As14Ge14Se72? x Sb x (where x = 3, 6, 9, 12 and 15 at%) thin films. Thin films with thickness 200–220 nm of As14Ge14Se72? x Sb x were prepared by thermal evaporation of the bulk samples. Increasing antimony content was found to affect the average heat of atomization, the average coordination number, number of constraints and cohesive energy of the As14Ge14Se72 ?x Sb x alloys. Optical absorption measurements showed that the fundamental absorption edge is a function of composition. Optical absorption is due to allowed, non-direct transition and the energy gap decreases with the increasing antimony content. The chemical bond approach has been applied successfully to interpret the decrease in the optical gap with increasing antimony content. 相似文献
6.
《Journal of Physics and Chemistry of Solids》2001,62(5):921-926
The optical absorption of As2Se3 thin films is studied in the UV–VIS spectral range and the value of the optical energy gap is determined. The effect of photo-irradiation on the optical absorption and transmission of thin film samples is also investigated. The optical energy gap was found to decrease with photo-irradiation time. The results of photo-irradiation are discussed in correlation with the structural aspects of As2Se3. A model is proposed to account for the structural changes, resulting from photo-irradiation, causing the decrease of the energy gap. The effect of γ-radiation on the optical absorption of As2Se3 thin films was studied also and no detectable effect on the value of the optical energy gap was observed. 相似文献
7.
The results of the femtosecond optical heterodyne detection of optical Kerr effect at 805 nm with the 80 fs ultrafast pulses in amorphous Ge10As40S30Se20 film is reported in this paper. The film shows an optical non-linear response of 200 fs under ultrafast 80 fs-pulse excitation, and the values of real and imaginary parts of non-linear susceptibility χ(3) were 9.0×10−12 and −4.0×10−12 esu, respectively. The large third-order non-linearity and ultrafast response are attributed to the ultrafast distortion of the electron orbits surrounding the average positions of the nucleus of Ge, As, S and Se atoms. This Ge10As40S30Se20 chalcogenide glass would be expected as a promising material for optical switching technique. 相似文献
8.
K.A. Aly A.M. Abd ElnaeimM.A.M. Uosif O. Abdel-Rahim 《Physica B: Condensed Matter》2011,406(22):4227-4232
Different compositions of GexAs10Te90−x (x=5, 10, 15, 20, and 25 at%) chalcogenide glasses were prepared by the usual melt quench technique. Amorphous GexAs10Te90−x thin films were deposited onto cleaned glass substrates using the thermal evaporation method. Transmission spectra, T(λ), of the films at normal incidence were measured in the wavelength range 400-2500 nm. A straightforward analysis proposed by Swanepoel based on the use of the maxima and minima of the interference fringes has been used to drive the film thickness, d, the complex index of refraction, n, and the extinction coefficient, k. It was found that, the addition of Ge content at the expense of Te atoms shifts the optical band gap to the short wavelength side (blue shift of the optical band gap) while the refractive index are found to decreases. The obtained results of the refractive index were discussed in terms of the electronic polarizability and the single-oscillator Wemple and DiDomenico model (WDD). The optical absorption is due to the allowed non-direct optical transitions. The observed increase in the optical band gap with the increase in Ge content was discussed in terms of the width of the tail states in the gap and the covalent bond approach. 相似文献
9.
Reversible and athermal photo-vitrification of As50Se50 thin films deposited onto silicon wafer and glass substrates 总被引:1,自引:0,他引:1
R. Prieto-Alcón E. Márquez J.M. González-Leal R. Jiménez-Garay A.V. Kolobov M. Frumar 《Applied Physics A: Materials Science & Processing》1999,68(6):653-661
Photo-vitrification of As50Se50 thin films deposited onto silicon wafer and glass substrates has been studied using X-ray diffraction, far-infrared, and
differential infrared spectroscopies. The optical study of this photo-amorphization effect has been carried out by two different
methods enabling the determination of the average thickness and refractive index of a wedge-shaped thin film. The refractive-index
behaviour of the as-evaporated, crystallized, and photo-vitrified As50Se50 films is analyzed within the single-oscillator approach. The optical-absorption edge is described using the non-direct transition
model, and the optical energy gap is calculated. In the course of the vitrification of an As50Se50 thin film deposited on a silicon substrate the photo-oxidation of the film has been additionally detected and arsenic trioxide
micro-crystals were formed on the surface of the film. Such oxidation has not been observed with As50Se50 films deposited on glass substrates, which demonstrates that the photo-vitrification phenomenon depends also on the type
of substrate. Finally, it is concluded from the optical study that a reversible photo-darkening effect accompanies the photo-induced
vitrification phenomenon.
Received: 3 August 1998 / Accepted: 13 January 1999 / Published online: 7 April 1999 相似文献
10.
The non-resonant third-order non-linear optical properties of amorphous Ge20As25Se55 films were studied experimentally by the method of the femtosecond optical heterodyne detection of optical Kerr effect. The real and imaginary parts of complex third-order optical non-linearity could be effectively separated and their values and signs could be also determined, which were 6.6 × 10−12 and −2.4 × 10−12 esu, respectively. Amorphous Ge20As25Se55 films showed a very fast response in the range of 200 fs under ultrafast excitation. The ultrafast response and large third-order non-linearity are attributed to the ultrafast distortion of the electron orbitals surrounding the average positions of the nucleus of Ge, As and Se atoms. The high third-order susceptibility and a fast response time of amorphous Ge20As25Se55 films makes it a promising material for application in advanced techniques especially in optical switching. 相似文献
11.
The optical, structural and thermal optimizations of Ge33As12Se55 glass were the aim of this study. In this regards, Ge33As12Se45M10 (M = Se, Te, S and S0.5Te0.5) glasses were synthesized by conventional melt quenching technique in quartz ampule. The prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The fundamental absorption edge for prepared samples was also analyzed in terms of the theory proposed by Davis and Mott. The addition of S and Te elements to melting batch has deleterious effects on optical properties of Ge33As12Se55 glass. Mg and Al can act as gettering elements for reduction of the intensity of oxide absorption bands from FTIR spectra (without any effects on optical properties of Ge33As12Se55 glass). The precipitation of GeSe phase, during crystallization process, has negligible effects on optical properties of Ge33As12Se55 glass. 相似文献
12.
In this paper, different homogenous compositions of Ge30? x Se70Ag x (0?≤?x?≤?30 at%) thin films were prepared by thermal evaporation. Reflection spectra, R(λ), for the films were measured in the wavelength range 400–2500?nm. A straightforward analysis proposed by Minkov [J. Phys. D: Appl. Phys. 22 (1989) p.1157], based on the maxima and minima of the reflection spectra, allows us to derive the real and imaginary parts of the complex index of refraction and the film thickness of the studied films. Increasing Ag content at the expense of Ge atoms is found to affect the refractive index and the extinction coefficient of the films. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple–DiDomenico model. Optical absorption measurements were used to obtain the fundamental absorption edge as a function of composition. With increasing Ag content, the refractive index increases while the optical band gap decreases. The compositional dependence of the optical band gap for the Ge30? x Se70Ag x (0?≤?x?≤?30) thin films is discussed in terms of the chemical bond approach. 相似文献
13.
《Journal of Physics and Chemistry of Solids》2007,68(5-6):993-997
Films of nominal composition Ge28Se60Sb12 were deposited on microscope slides by pulsed laser deposition (PLD), using either bulk or powdered glassy targets and a Nd:YAG laser (λ=266 nm). The films with thickness comprised between 400 and 800 nm showed a smooth and dense morphology. They were homogeneous in composition all over the samples with a composition somewhat deficient in selenium compared to the nominal one: Ge28.1±0.3Se56.1±0.1Sb15.8±0.2 and Ge29.0±0.3Se55.5±0.1Sb15.5±0.2 for films obtained from powdered glassy targets and bulk targets, respectively. The optical characteristics of the films were extracted from the transmission spectra recorded between 250 and 2500 nm. In particular, the refractive index at 1.5 μm was found to be 2.75±0.03, close to that of the bulk glass, as expected for dense films. The decrease in the optical band gap and the increase in the Urbach absorption edge with the film thickness were attributed to an increase in disorder. 相似文献
14.
F.A. Al-Agel 《Optics & Laser Technology》2011,43(4):781-786
Bulk Ge20Se80−xTlx (x ranging from 0 to 15 at%) chalcogenide glasses were prepared by conventional melt quenching technique. Thin films of these compositions were prepared by thermal evaporation, on glass and Si wafer substrates at a base pressure of 10−6 Torr. X-ray diffraction studies were performed to investigate the structure of the thin films. The absence of any sharp peaks in the X-ray diffractogram confirms that the films are amorphous in nature. The optical constants (absorption coefficient, optical band gap, extinction coefficient and refractive index) of Ge20Se80−xTlx thin films are determined by absorption and reflectance measurements in a wavelength range of 400-900 nm. In order to determine the optical gap, the absorption spectra of films with different Tl contents were analyzed. The absorption data revealed the existence of allowed indirect transitions. The optical band gap showed a sharp decrease from 2.06 to 1.79 eV as the Tl content increased from 0% to 15%. It has been found that the values of absorption coefficient and refractive index increase while the extinction coefficient decreases with increase in Tl content in the Ge-Se system. These results are interpreted in terms of the change in concentration of localized states due to the shift in Fermi level. DC electrical conductivity of Ge20Se80−xTlx thin films was carried out in a temperature range 293-393 K. The electrical activation energy of these films was determined by investigating the temperature dependence of dc conductivity. A decrease in the electrical activation energy from 0.91 to 0.55 eV was observed as the Tl content was increased up to 15 at% in Ge20Se80−xTlx system. On the basis of pre-exponential factor, it is suggested that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. 相似文献
15.
As20Se60Tl20 bulk material was prepared firstly then thermal evaporation method was used to prepare As20Se60Tl20 films. Illumination effect at room temperature for the mentioned films has been studied within the homogeneous glass-forming region. The prepared film samples were amorphous, this is depicted by X-ray chart. Optical properties have been studied using spectrophotometric measurements. The absorption edge was shifted to shorter wavelengths due to light exposure or photobleaching effect. It was found that the extinction coefficient and the optical band gap have opposite character after illumination. 相似文献
16.
H. T. El-Shair 《Applied Physics A: Materials Science & Processing》1991,53(2):164-167
Electrical, optical and structural, properties, of Te40As38Ge10Si10 thin films were studied. X-ray diffraction patterns indicate that these films are in an amorphous state. The dark electrical resistivity of Te40As38Ge10Si12 films was measured at room temperature and at elevated temperature. The thermal activation energy E was determined. The optical constants (refractive index n and absorption index k) of such films were determined in the spectral range of 0.5–2.0 m. The absorption coefficient () of this system was also determined using the known equation =4k/. The refractive index n has anomalous behaviour near the absorption edge. Analysis of the absorption spectrum reveals indirect optical transitions. The corresponding forbidden-band width was determined. Its value is approximately twice the thermal activation energy. 相似文献
17.
Kamal A. Aly 《Applied Physics A: Materials Science & Processing》2010,99(4):913-919
Amorphous As x Se70Te30?x thin films with (0≤x≤30 at.%) were deposited onto glass substrates by using thermal evaporation method. The transmission spectra T(λ) of the films at normal incidence were measured in the wavelength range 400–2500 nm. A straightforward analysis proposed by Swanepoel based on the use of the maxima and minima of the interference fringes has been used to drive the film thickness, d, the complex index of refraction, n, and the extinction coefficient, k. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple and DiDomenico model (WDD). Increasing As content is found to affect the refractive index and the extinction coefficient of the As x Se70Te30?x films. With increasing As content the optical band gap increases while the refractive index decreases. The optical absorption is due to allowed indirect transition. The chemical bond approach has been applied successfully to interpret the increase of the optical gap with increasing As content. 相似文献
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20.
This paper reports on the results of investigations into the nonlinear optical characteristics of chalcogenide films (As2S3, As20S80, 2As2S3/As2Se3, 3As2S3/As2Se3). The nonlinear refractive indices and two-photon absorption coefficients for these films are measured using the Z-scan technique at wavelengths of a picosecond Nd: YAG laser (λ=1064 and 532 nm). The optical limiting due to Kerr-type nonlinearities is analyzed. 相似文献