Browsing Physics by Author "Sathiaraj, T.S."
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Sathiaraj, T.S. (Elsevier Ltd, NaN, 2008)[more][less]
Abstract: Indium tin oxide (ITO) thin films were prepared by RF sputtering of ceramic ITO target in pure argon atmosphere at a high base pressure of 3 10 4mbar without substrate heating and oxygen admittance. The use of pure argon during deposition resulted in films with high transparency (80–85%) in the visible and IR wavelength region. The films were subsequently annealed in air in the temperature range 100–400 1C. The annealed films show decreased transmittance in the IR region and decreased resistivity. The films were characterized by electron microscopy, spectrophotometry and XRD. The predominant orientation of the films is (2 2 2) instead of (4 0 0). The transmission and reflection spectra in the wavelength range 300–2500 nm are used to study the optical behaviour of the films. The optical transmittance and reflectance spectra of the films were simultaneously simulated with different dielectric function models. The best fit of the spectrophotometric data was obtained using the frequency-dependent damping constant in the Drude model coupled with the Bruggeman effective medium theory for the surface roughness. It has been found that the sputtering power and the chamber residual pressure play a key role in the resulting optical properties. This paper presents the refractive index profile, the structure determined from the XRD and the electrical properties of ITO films. It has been found from the electrical measurement that films sputtered at 200W power and subsequently annealed at 400 1C have a sheet resistance of 80O/& and resistivity of 1.9 10 3Ocm. Description: Some mathematical symbols may not come as they are in the abstract. URI: http://hdl.handle.net/10311/690 Files in this item: 1
Effect of annealing.pdf (1.308Mb) -
Sathiaraj, T.S. (Elsevier Science Ltd. http://www.elsevier.com/locate/mejo, NaN, 2008)[more][less]
Abstract: Indium tin oxide (ITO) thin films were prepared by RF sputtering of ceramic ITO target in pure argon atmosphere at a high base pressure of 3×10−4 mbar without substrate heating and oxygen admittance. The use of pure argon during deposition resulted in films with high transparency (80–85%) in the visible and IR wavelength region. The films were subsequently annealed in air in the temperature range 100–400 °C. The annealed films show decreased transmittance in the IR region and decreased resistivity. The films were characterized by electron microscopy, spectrophotometry and XRD. The predominant orientation of the films is (2 2 2) instead of (4 0 0). The transmission and reflection spectra in the wavelength range 300–2500 nm are used to study the optical behaviour of the films. The optical transmittance and reflectance spectra of the films were simultaneously simulated with different dielectric function models. The best fit of the spectrophotometric data was obtained using the frequency-dependent damping constant in the Drude model coupled with the Bruggeman effective medium theory for the surface roughness. It has been found that the sputtering power and the chamber residual pressure play a key role in the resulting optical properties. This paper presents the refractive index profile, the structure determined from the XRD and the electrical properties of ITO films. It has been found from the electrical measurement that films sputtered at 200 W power and subsequently annealed at 400 °C have a sheet resistance of 80 Ω/□ and resistivity of 1.9×10−3 Ωcm. URI: http://hdl.handle.net/10311/631 Files in this item: 1
Sathiaraj_MJ_2008.pdf (763.9Kb) -
Kumar, J.; Kumar, P.; Suri, N.; Ahmad, M.; Thangaraj, R.; Sathiaraj, T.S. ( NaN, 2008)[more][less]
Abstract: Optical properties of Pb doped ternary Ge-Sb-Te chalcognide films prepared by thermal evaporation have been studied in the visible and near-infrared spectral regions. The straightforward analysis proposed by Swanepoel has been successfully employed and it has allowed us to accurately determine the refractive index and extinction coefficient of the films. The refractive index has been determined from the upper and lower envelopes of the transmission spectra. The absorption coefficient and extinction coefficient have been determined from the transmission spectra in the strong-absorption region. The dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single oscillator model. URI: http://hdl.handle.net/10311/544 Files in this item: 1
Effect of composition.pdf (950.3Kb) -
Ahmad, M.; Thangaraj, R.; Sathiaraj, T.S. (Springer, NaN, 2010)[more][less]
Abstract: Bulk samples of Sn10Sb20-xBixSe70 (0 B x B 8) chalcogenide alloys were prepared by the conventional melt quenching technique. Thin films were prepared on wellcleaned glass substrates by thermal evaporation technique. X-ray diffraction studies revealed that the alloys with x = 0 and 2 at.% of Bi were amorphous, whereas the alloys with x = 4, 6, 8 at.% were crystalline. The crystalline phases are identified as due to the formation of Bi2Se3 and BiSe2 phases. The microstructural and differential scanning calorimetric studies show the presence of these phases. A simple, straight forward procedure suggested by Swanepoel has been used to calculate the optical parameters, refractive index, and extinction coefficient. The optical gap for all the samples has been obtained from the Tauc plots. The variation in optical parameters for different Bi concentration has been explained on the basis of presence of defect states and the change in stoichiometry with the change in Bi concentration. Description: some symbols on the abstract may not appear as they are on the text. URI: http://hdl.handle.net/10311/752 Files in this item: 1
Heterogeneous crystallization.pdf (777.8Kb) -
Kumar, P.; Sathiaraj, T.S.; Thangaraj, R. (Taylor & Francis, NaN, 2010)[more][less]
Abstract: The measurements and analysis of optical transmission and far-infrared (IR) reflectivity spectra of thermally evaporated Sb2Se3:Sn films are reported. The refractive index and film thickness have been determined from the upper and lower envelopes of the transmission spectra (Swanepoel’s standard envelope method), measured at normal incidence, in the spectral range from 800 to 2500 nm. Values of the refractive index fit well to Cauchy’s dispersion relation. The optical gap decreases with an increase in the Sn content, while a maximum in the tailing parameter and Urbach’s energy occurs with only a small amount ( 1 at %) of this additive. Characteristic vibrational bands for SbSe3 structural units are revealed in the far-IR spectrum with no additional ones arising from the Sn additive. The Kramers–Kronig analysis has been used to calculate the dielectric constants and hence the longitudinal optic and transverse optic splitting for various compositions. The inclusion of Sn as a charged entity along with the Coulomb interactions which serve to polarize the glass medium is found to be responsible for these results. URI: http://hdl.handle.net/10311/547 Files in this item: 1
Optical properties.pdf (1.116Mb) -
Kumar, J.; Ahmad, M.; Chander, R.; Thangaraj, R.; Sathiaraj, T.S. (EDP Sciences, NaN, 2008)[more][less]
Abstract: Effect of Pb substitution on the amorphous-crystalline transformation temperature, optical band gap and crystalline structure of Ge2Sb2Te5 has been studied. In Pb:GeSbTe chalcogenide films prepared by thermal evaporation, an amorphous to crystallization transition is observed at 124, 129, 136 and 138 ◦C in Pb0Ge20Sb24Te56, Pb1.6Ge19Sb26Te54, Pb3Ge17Sb28Te53 and Pb5Ge12Sb28Te55 respectively. XRD investigations of annealed samples reveal that Pb substitution retains NaCl type crystalline structure of GST but expands the lattice due to large atomic radii. The increase in amorphous-crystalline transformation temperature is followed with the increase in phase segregation. The optical gap shows marginal variations with composition. URI: http://hdl.handle.net/10311/531 Files in this item: 1
Phase segregation.pdf (573.5Kb) -
Kumar, J.; Ahmad, M.; Chander, R.; Thangaraj, R.; Sathiaraj, T.S. (EDP Sciences. http://www.epjap.org/, NaN, 2008)[more][less]
Abstract: Effect of Pb substitution on the amorphous-crystalline transformation temperature, optical band gap and crystalline structure of Ge2Sb2Te5 has been studied. In Pb:GeSbTe chalcogenide films prepared by thermal evaporation, an amorphous to crystallization transition is observed at 124, 129, 136 and 138 ◦C in Pb0Ge20Sb24Te56, Pb1.6Ge19Sb26Te54, Pb3Ge17Sb28Te53 and Pb5Ge12Sb28Te55 respectively. XRD investigations of annealed samples reveal that Pb substitution retains NaCl type crystalline structure of GST but expands the lattice due to large atomic radii. The increase in amorphous-crystalline transformation temperature is followed with the increase in phase segregation. The optical gap shows marginal variations with composition. URI: http://hdl.handle.net/10311/278 Files in this item: 1
Kumar_EPJAP41_2008.pdf (796.1Kb) -
Thermal annealing dependence of some physical propertiesof Bi-substituted Sn–Sb–Se glassy thin filmsAhmad, M.; Thangaraj, R.; Sathiaraj, T.S. (EDP Sciences, NaN, 2009)[more][less]
Abstract: Bulk glasses of the Sn10Sb20−xBixSe70 (0 x 8) system were prepared by the conventional melt quenching technique. Thin films were prepared by the thermal evaporation technique on glass substrates. Appearance of some crystalline phases is observed from the X-ray diffractograms after heat treatment below the glass transition temperature for 1 h. Scanning electron microscopy studies also show the presence of microcrystalline phases in the amorphous matrix after annealing for 1 h. The effect of Bi concentration and heat treatment on the optical gap and activation energy for dark conductivity were also investigated for the pristine as well as annealed films. The results are discussed on the basis of models related to the presence of defect states in chalcogenide materials. URI: http://hdl.handle.net/10311/534 Files in this item: 1
Thermal annealing dependence.pdf (822.7Kb)
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