Infrared Reflectance from Mat Surfaces

Chalcogenide glasses have attracted much attention largely due to their interesting physical and chemical properties. Though few published articles exist on the As-Te system, little is known about the optical properties of eutectic or near eutectic composition of As-Te system upon heat treatment. Therefore, this paper reports the effects of annealing temperature on the structural and optical parameters of As 30 Te 70 thin films. The bulk and thin films of 150 nm thick As 30 Te 70 chalcogenide glasses were prepared by melt-quenching and thermal evaporation techniques, respectively. The glass transition and crystallization reactions of the bulk samples were investigated using differential scanning calorimetry (DSC). The influence of annealing temperature on the transformation of the crystal structure was studied by X-ray diffraction (XRD), while the surface morphology of the annealed samples was examined using scanning electron microscope (SEM). The optical band gap, refractive index and extinction coefficient were also calculated. The DSC scans showed that the melting temperature remains constant at 636.56 K. In addition, other characteristic temperatures such as the glass transition temperature, the onset crystallization temperature, and the crystallization peak temperature increase with increasing the heating rate. The crystalline phases for the as-prepared and annealed films consist of orthorhombic As, hexagonal Te, and monoclinic As 2 Te 3 phases. Furthermore, the average crystallite size, strain, and dislocation density depend on the annealing temperature. The optical absorption results revealed that the investigated films have a direct transition, and their optical energy gap decreases from 1.82 eV to 1.49 eV as the annealing temperature increases up to 433 K. However, the refractive index, extinction coefficient, dielectric constant and the ratio of free carrier concentration to its effective mass, increase with increasing the annealing temperature.

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“…The refractive index (n), and extinction coefficient (k ex ) of the studied films have been estimated using the following relations [37,38]:…”

Section: Dispersion Optical Constantsmentioning

confidence: 99%

Influence of annealing temperature on the structural and optical properties of As₃₀Te₇₀ thin films

Abd‐Elnaiem

Mohamed

Hassan

et al. 2017

Materials Science-Poland

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“…Some coatings exhibit a 26 µm feature and others do not, which indicates variations in preferred crystal growth [Onari et al, 1977;Pecharoman and Inglesias, 2000]. Potential causes of other spectral variations include scattering, optical, and preferred crystal orientation effects, and contaminants [Vincent and Hunt, 1968;Estep-Barnes, 1977;Onari et al, 1977;Pecharoman and Inglesias, 2000;Estep-Barnes, 1972;Salisbury et al, 1991;Lane et al, 2002]. Those effects have received almost no attention for a hematite coating.…”

Section: Comparison To Tes Datamentioning

confidence: 99%

“…Material can scatter light through surface or volume scattering [Vincent and Hunt, 1968;Hapke, 1993]. A strong absorption causes high opacity, and the resulting mirror-like surface reflectance ("surface scattering") causes a clear emissivity trough (a spectral band) because radiance exiting the material is reflected inward ( Figure 1, "solid surface") [Planck, 1914].…”

Section: Introductionmentioning

confidence: 99%

“…Volume scattering causes a reststrahlen band emission peak, (Figure 1, lower trace), which counters the surface scattering trough, and thus causes low spectral contrast (Figure 1, upper trace) [Vincent and Hunt, 1968;Salisbury et al, 1991;Salisbury and Wald, 1992]. The lower trace shows the spectrum measured of a hematite hand sample ("grhemfrhr").…”

Section: Introductionmentioning

confidence: 99%

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Lunar and Planetary Institute

2006

Choice Reviews Online

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“…In relatively transparent materials, light is scattered out of fine-grained samples before much absorption takes place, resulting in spectra that have weak absorption bands and a bright background or "continuum" (Vincent and Hunt, 1968). Coarser samples commonly show more pronounced absorption bands, although in very coarse-grained materials both the continuum reflectance and the band depths can be reduced (Adams and Filice, 1967).…”

Section: Introductionmentioning

confidence: 99%

Near-Infrared Reflectance Spectra of Mixtures of Kaolin-Group Minerals: Use in Clay Mineral Studies

Crowley

Vergo

1988

Clays and clay miner.

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Abstract--Near-infrared (NIR) reflectance spectra for mixtures of ordered kaolinite and ordered dickite have been found to simulate the spectral response of disordered kaolinite. The amount of octahedral vacancy disorder in nine disordered kaolinite samples was estimated by comparing the sample spectra to the spectra of reference mixtures. The resulting estimates are consistent with previously published estimates of vacancy disorder for similar kaolin minerals that were modeled from calculated X-ray diffraction patterns. The ordered kaolinite and dickite samples used in the reference mixtures were carefully selected to avoid undesirable particle size effects that could bias the spectral results.NIR spectra were also recorded for laboratory mixtures of ordered kaolinite and halloysite to assess whether the spectra could be potentially useful for determining mineral proportions in natural physical mixtures of these two clays. Although the kaolinite-halloysite proportions could only be roughly estimated from the mixture spectra, the halloysite component was evident even when halloysite was present in only minor amounts. A similar approach using NIR spectra for laboratory mixtures may have applications in other studies of natural clay mixtures.

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Infrared Reflectance from Mat Surfaces

Cited by 192 publications

References 9 publications

Influence of annealing temperature on the structural and optical properties of As₃₀Te₇₀ thin films

Influence of annealing temperature on the structural and optical properties of As₃₀Te₇₀ thin films

Lunar and Planetary Institute

Near-Infrared Reflectance Spectra of Mixtures of Kaolin-Group Minerals: Use in Clay Mineral Studies

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Infrared Reflectance from Mat Surfaces

Cited by 192 publications

References 9 publications

Influence of annealing temperature on the structural and optical properties of As30Te70 thin films

Influence of annealing temperature on the structural and optical properties of As30Te70 thin films

Lunar and Planetary Institute

Near-Infrared Reflectance Spectra of Mixtures of Kaolin-Group Minerals: Use in Clay Mineral Studies

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Influence of annealing temperature on the structural and optical properties of As₃₀Te₇₀ thin films

Influence of annealing temperature on the structural and optical properties of As₃₀Te₇₀ thin films