Optical properties of selenium–tellurium nanostructured thin film grown by thermal evaporation
TL;DR: In this article, the surface morphology of Se-Te thin films was investigated through Scanning Electron Microscopy (SEM) and XRD analysis was performed to confirm glassy nature of the nanostructured thin films.
Abstract: Se–Te nanostructured thin films were deposited on glass substrates in the presence of oxygen and argon by thermal evaporation. The properties of Se–Te thin films strongly depend on the deposition method. During the process used, the substrate is cooled to a temperature of 77 K employing liquid nitrogen. The nanostructured thin films of Se 100− x Te x (where x =4, 8 and 16) are deposited on glass substrate. The surface morphology of the deposited films was investigated through Scanning Electron Microscopy (SEM). The typical size of these nanostructures is in the range 40–100 nm and the length is of the order of several micrometers. The optical parameters i.e. optical gap ( E g ), absorption coefficient ( α ), and extinction coefficient ( k ) are calculated in the wavelength range 190–1100 nm. It was found that the optical band gap decreased from 3.4 to 2.9 eV when Te concentration was increased in the Se 100− x Te x nanostructured thin films. The large bandgap may be attributed to the decrease in particle size which clearly exhibits a quantum size effect. XRD analysis was performed to confirm glassy nature of the nanostructured thin films.
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TL;DR: In this article, the authors evaluated the physiological response of a chrysosporium to tellurium and selenium oxyanion oxyanions in the environment, which poses a strong concern due to their inherent toxicity at high concentrations, and the potential to exploit this fungus for bioremediation applications and for the biosynthesis of unique nanoparticles.
41 citations
TL;DR: The electrical and optical studies of thin films of a-GaxSe100−x nanorods have been synthesized thermal evaporation technique and it is suggested that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges.
Abstract: We report the electrical and optical studies of thin films of a-GaxSe100−x nanorods (x = 3, 6, 9 and 12). Thin films of a-GaxSe100−x nanorods have been synthesized thermal evaporation technique. DC electrical conductivity of deposited thin films of a-GaxSe100−x nanorods is measured as a function of temperature range from 298 to 383 K. An exponential increase in the dc conductivity is observed with the increase in temperature, suggesting thereby a semiconducting behavior. The estimated value of activation energy decreases on incorporation of dopant (Ga) content in the Se system. The calculated value of pre-exponential factor (σ0) is of the order of 101 Ω−1 cm−1, which suggests that the conduction takes place in the band tails of localized states. It is suggested that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. On the basis of the optical absorption measurements, an indirect optical band gap is observed in this system, and the value of optical band gap decreases on increasing Ga concentration.
39 citations
TL;DR: In this paper, structural and optical studies of Se88Te12 chalcogenide nanoparticles prepared by ball milling were performed in a Laboratory 8000 M-Mixer/Mill (SPEX) mill using hardened steel balls and a vial with a ball-to-powder weight ratio of 10:1.
26 citations
TL;DR: In this paper, thin films of Se35Te65-xGex (x = 0, 3, 6, 9, 12) nanoparticles were synthesized using thermal evaporation method using X-ray diffraction (XRD), scanning electron microscope (SEM), and absorption and transmission spectra.
Abstract: Thin films of Se35Te65-xGex (x = 0, 3, 6, 9, 12) nanoparticles were synthesized using thermal evaporation method. They were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and absorption and transmission spectra. XRD results show that these films are of amorphous nature, while SEM images show nanoparticles with average particle size around 30 nm. No significant changes are observed in morphology of the deposited films by changing concentrations of Te and Ge. The optical behaviors of these films have been studied using the absorption and transmission spectra in the spectral region 400- 1100 nm. The absorption, extinction coefficients and refractive index were obtained and investigated in more detail. The optical band gap (Eg) values were also determined and are found to decrease from 0.83 to 0.69 eV by increasing the concentration of Ge from 0 to 12. The transmission spectra for the thin films of Se35Te65-xGex nanoparticles show strong absorption at wavelength less than 500 nm and become highly transparent at wavelength above 800 nm. No significant changes in the transmission spectra are observed by increasing concentration of Ge. These results might be useful for development of optical disks and other semiconducting devices based on these nanochalcogenides.
19 citations
Cites background from "Optical properties of selenium–tell..."
...[5] have studied the optical properties of Se-Te nanostructured thin films grown by thermal evaporation, and Kotkata et al....
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TL;DR: In this article, the authors measured the dc electrical conductivity of the as-deposited films of Ga x Te100−x nanoparticles and found that the conduction is due to thermally assisted tunneling of carriers in localized states near the band edges.
Abstract: Thin films of Ga x Te100− x (x = 3, 6, 9 and 12) have been synthesized by thermal evaporation. From SEM images, it is observed that all the films contain nanoparticles of sizes varying from 100 to 200 nm. The dc electrical conductivity of the as-deposited films of Ga x Te100−x nanoparticles is measured as a function of temperature range from 298 to 383 K, and increases exponentially with temperature. The value of the activation energy, calculated from the slope of ln σ dc versus 1000/T plots, is found to decrease with increase in the Ga content. On the basis of the value of the pre-exponential factor σ o, it is suggested that the conduction is due to thermally assisted tunneling of carriers in localized states near the band edges. The optical measurements suggest an indirect optical band gap in this system. The value of the optical band gap decreases on increasing the Ga concentration.
15 citations
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TL;DR: Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated and self-organized, <0001> oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process.
Abstract: Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated The self-organized, oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process These wide band-gap semiconductor nanowires form natural laser cavities with diameters varying from 20 to 150 nanometers and lengths up to 10 micrometers Under optical excitation, surface-emitting lasing action was observed at 385 nanometers, with an emission linewidth less than 03 nanometer The chemical flexibility and the one-dimensionality of the nanowires make them ideal miniaturized laser light sources These short-wavelength nanolasers could have myriad applications, including optical computing, information storage, and microanalysis
8,592 citations
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01 Jan 1940
TL;DR: The Fermi Glass and the Anderson Transition as discussed by the authorsermi glass and Anderson transition have been studied in the context of non-crystalline Semiconductors, such as tetrahedrally-bonded semiconductors.
Abstract: 1. Introduction 2. Theory of Electrons in a Non-Crystalline Medium 3. Phonons and Polarons 4. The Fermi Glass and the Anderson Transition 5. Liquid Metals and Semimetals 6. Non-Crystalline Semiconductors 7. Tetrahedrally-Bonded Semiconductors - Amorphous Germanium and Silicon 8. Aresnic and Other Three-Fold Co-ordinated Materials 9. Chalcogenide and Other Glasses 10. Selenium, Tellurium, and their Alloys
8,188 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.
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