Ambika Sharma

Linear and nonlinear optical properties of new Se-based quaternary Se–Sn–(Bi,Te) chalcogenide thin films

We are reporting the linear and nonlinear optical properties of Se-based quaternary chalcogenide Se–Sn–(Bi,Te) thin films. Thin films of bulk chalcogenide glasses, prepared by melt quenching method are deposited on glass substrate using thermal evaporation technique. The optical behavior of studied chalcogenide glass systems is investigated using transmission spectra in the spectral range of 400–2500 nm. The glasses exhibit considerable optical nonlinearities which are estimated using linear optical parameters. Linear refractive index has been calculated using well-known Swanepoel method. Wemple-DiDomenico (WDD) parameters are also reported for the investigated glasses. Optical band gap is determined using Tauc extrapolation method and is observed to increase with Sn content. The formulation proposed by Fournier and Snitzer is used to determine the nonlinear behavior of the refractive index. It is observed that n2 increases linearly with increasing n. The values of n2 are compared with pure silica and the results are 100–600 orders higher. The third-order susceptibility χ(3) is also reported in this paper. Two-photon absorption coefficient β2 is determined using optical band gap data. A strong dependence of β2 and n2 is observed on normalized photon energy () for a fixed excitation wavelength (1064 nm).

Temperature and frequency dependence of AC conductivity of new quaternary Se-Te-Bi-Pb chalcogenide glasses

The aim of the present work is to study the temperature and frequency dependence of ac conductivity of new quaternary Se84-xTe15Bi1.0Pbx chalcogenide glasses. The Se84-xTe15Bi1.0Pbx (x = 2, 6) glassy alloys are prepared by using melt quenching technique. The temperature and frequency dependent behavior of ac conductivity σac(ω) has been carried out in the frequency range 42 Hz to 5 MHz and in the temperature range of 298-323 K below glass transition temperature. The behavior of ac conductivity is described in terms of the power law ωs. The obtained temperature dependence behavior of ac conductivity and frequency component (s) are explained by means of correlated barrier hopping model recommended by Elliot.

Study of Conduction Mechanism in Amorphous Se85-xTe15Bix Thin Films

Bulk samples of Se85-xTe15Bix (where x = 0, 1, 2, 3, 4, 5) glassy alloys are prepared by melt quenching technique. Thin films of the corresponding bulk samples are prepared by vacuum evaporation technique. I-V characteristics of Se85-xTe15Bix thin films are studied using Keithley 6487 picoammeter. Linear behavior of current has been observed at low voltage range and current is found to deviate from linearity i.e. tend towards non-Ohmic behavior in the higher voltage range. The value of resistance is also calculated in three different voltage ranges (0-90 V), (110-200 V) and (220-300 V) for the films under consideration. Maximum resistance has been observed for x = 1 and minimum resistance for x = 5. The conduction mechanism is discussed qualitatively and it is found to be of Poole Frenkel type for higher voltage range.

Effect of Bi Additions upon the Physical Properties of Germanium Telluride Glassy Semiconductors

The effect of bismuth (Bi) additions upon the physical properties, coordination number (m), constraints (Nc), density (ρ), molar volume (Vm), cohesive energy (CE), lone pair electrons (L) and glass transition temperature (Tg) of Ge20Te80-xBix (x = 0, 1.5, 2.5, 5.0) bulk glassy alloy has been investigated. The density and molar volume of the glassy alloys has been found to increase with increasing Bi content. The CE of the investigated samples has been calculated by using the chemical bond approach (CBA) and is correlated with a decrease in the optical band-gap with increasing Bi content. The glass transition temperature has been estimated by using the Tichy–Ticha approach and was found to increase with an increase in the Bi content.

Mutagenic primer-based PCR-RFLP assay for genotyping IRGM gene promoter variant rs4958843 (C/T)

Single‐nucleotide polymorphisms play an important role in the susceptibility of many diseases, evolutionary studies, and genetic mapping. The rs4958843 in IRGM promoter is associated with tuberculosis and Crohns disease. As this SNP is not present in any of the restriction sites, PCR‐RFLP is not possible. Therefore, we have developed artificial‐RFLP method to genotype this SNP.

Effect of Sn doping on nonlinear optical properties of quaternary Se-Sn-(Bi,Te) chalcogenide thin films

The aim of this work is to report the effect of Sn doping on the third order nonlinear optical properties of chalcogenide Se84-xTe15Bi1.0Snx thin films. Melt quenching technique has been used for the preparation of bulk chalcogenide glasses. Thin films of the studied composition are deposited on cleaned glass substrate by thermal evaporation technique. Optical band gap (Eg) is calculated by using Tauc extrapolation method and is found to increase from 1.27 eV to 1.64 eV with the incorporation of Sn content. Stryland approach is utilized for the calculation of two photon absorption coefficient (β2). The nonlinear refractive index (n2) and third order susceptibility (χ(3) are calculated using Tichy and Ticha approach. The result shows that nonlinear refractive index (n2) follows the same trend as that of linear refractive index (n). The values of n2 of studied composition as compared to pure silica are 1000-5000 times higher.

Study of optical nonlinearities in Se-Te-Bi thin films

The present work reports the nonlinear refractive index of Se85−xTe15Bix thin films calculated by Ticha and Tichy relation. The nonlinear refractive index of Chalcogenide amorphous semiconductor is well correlated with the linear refractive index and WDD parameters which in turn depend on the density and molar volume of the system. The density of the system is calculated theoretical as well as experimentally by using Archimedes principle. The linear refractive index and WDD parameters are calculated using single transmission spectra in the spectral range of 400-1500 nm. It is observed that linear as well as nonlinear refractive index increases with Bi content. The results are analyzed on the basis of increasing polarizability due to larger radii of Bi.

Composition dependent linear and nonlinear refractive index of new Sn based chalcogenide thin films

Present paper reports the linear (n) and nonlinear refractive index (n2) of Sn based Se-Te-Bi chalcogenide thin films. n is calculated using Swanepoel’s method and n2 is calculated by Boling formula and compared with silica.

Study of conduction mechanism in amorphous Ge20Te80-xBix (x = 0, 1.5, 2.5, 5.0) chalcogenide glassy alloys

I-V characteristics of Ge20Te80-xBix chalcogenide thin films, prepared by vacuum evaporation technique are studied using Keithley 6487 picoammeter. For x = 0, 1.5, current follows linear behavior in the range 0—100V. However for x = 2.5 and 5.0 current deviates from linearity in the higher voltage range. The conduction mechanism is discussed in these samples (x = 2.5, 5.0) and is found to follow linear behavior in the range 0-40V. However for V > 40V it is found to be of Poole Frenkel type. The value of resistance is calculated for different samples and at different voltage ranges.

ELECTRICAL AND PHOTOELECTRICAL PROPERTIES OF A-Ge20Te80-xBix (x = 0, 1.5, 2.5, 5.0) THIN FILMS

Bulk samples of Te-rich Ge20Te80-xBix (x = 0, 1.5, 2.5, 5.0) glassy alloys are prepared by melt quenching technique. The thin films of the bulk samples are deposited by using vacuum evaporation technique for their electrical and photoelectrical measurements. Keithley 6487 picoammeter has been used to study the electrical and photoelectrical characteristics of Ge20Te80-XBix thin films kept in vacuum. Temperature dependent dark and photoconductivity is studied in the temperature range 300-360 K and voltage V = 80V. Photoconductivity with intensity at room temperature follows a power law where power γ lies near to 0.5, suggesting that the recombination is bimolecular in nature. The density of defect states and photosensitivity are found to follow an opposite trend with each other. The differential life time is determined from the rise and decay of photocurrent w.r.t. time. The dispersion parameter and localized state distribution parameter are estimated from decay curves and reported for the studied composition.