S. Asokan

Glass formation in germanium telluride glasses containing metallic additives

Differential scanning calorimetric (DSC) studies have been carried out on germanium telluride glasses containing Cu and Ag. Both CuxGe15Te852xO2 # x # 10U and AgxGe15Te852xO2:5 # x # 21:5U glasses are found to exhibit single glass transition and single crystallization. On the basis of the devitrification behaviour of these glasses one can conclude that the network connectivity of the parent Ge‐Te matrix is not improved by the addition of Cu whereas Ag improves the connectivity. Overconstraining of the structural network for x . 5 is rapid in Cu added glasses and more gradual in Ag added glasses. The difference in the glass formation in the Cu‐Ge‐Te and Ag‐Ge‐Te systems is understood in light of the above differences in the structural network. q 1999 Elsevier Science Ltd. All rights reserved.

Composition tunable memory and threshold switching in Al20As xTe80− x semiconducting glasses

I-V studies indicate a composition dependent switching behavior (Memory or Threshold) in bulk Al20AsxTe80−x glasses, which is determined by the coordination and composition of aluminum. Investigations on temperature and thickness dependence of switching and structural studies on switched samples suggest thermal and electronic mechanisms of switching for the memory and threshold samples, respectively. The present results also show that these samples have a wider composition range of threshold behavior with lower threshold voltages compared to other threshold samples.

Composition dependence of photoconductivity of Al20AsxTe80−x glasses

The time dependent photocurrent of

High-pressure resistivity behavior of As–Te–In glasses – the effect of network topological thresholds

Al_2_0 As_x Te_8_0 - x

Tomographic imaging of phase objects in turbid media through quantitative estimate of phase of ballistic light

glasses has been studied at low temperatures. It is found that the photocurrent of all the

Strip inverse-configuration photopyroelectric technique to measure the thermal conductivity of bulk samples

Al_2_0 As_x Te_8_0 - x

Direct measurement of phase of foreward-scattered light using polarization heterodyne interferometer

samples studied does not decrease appreciably during illumination, which is consistent with the behavior of other narrow band gap amorphous chalcogenides. Further, the photosensitivity is found to be maximized for the composition x=25, which can be associated with rigidity percolation.

Influence of chemical disorder on electrical switching in chalcogenide glasses

Abstract Electrical resistivity measurements have been carried out on As–Te–In glasses up to a pressure of 8 GPa using an Opposed Anvil Cell. It is found that the electrical resistivity and conductivity activation energy decrease continuously with pressure and the samples become metallic at pressures in the range 1.5–2.5 GPa. The variation with composition of the normalized electrical resistivity at different pressures suggests the possibility of rigidity percolation and chemical thresholds occurring around the average coordination of 〈 r 〉=2.65 and 2.7 respectively. It is also observed that As–Te–In samples remain amorphous when they undergo metallization at high pressures, which is analogous to the threshold switching exhibited by these samples.

Electrical switching in chalcogenide glasses - Some newer insights

We demonstrate experimental measurement of phase of the ballistic and near-ballistic component of light transmitted through scattering media. This is done through measurement of transport of intensity of the ballistic component whose strength is measured using polarization gating. The measured phase of the ballistic light is inverted using filtered backprojection algorithm and the reconstructed real refractive index for an optical fiber hidden in a scattering media is presented.

TRANSIENT AND STEADY STATE PHOTOCONDUCTIVITY STUDIES ON BULK GLASSES AND AMORPHOUS FILMS OF Ge-Te-Pb - COMPOSITION AND SPECTRAL DEPENDENCE

The strip inverse-configuration photopyroelectric technique to measure the thermal conductivity of bulk samples of metals, semiconductors, and insulators is presented. It utilizes a narrow (500 μm wide) strip of a 9 μm thick pyroelectric sensor in an inverse configuration. A mathematical model is outlined that yields an expression for the output voltage of the pyroelectric sensor following heat dissipation into the sample, in a frequency range where the proposed measurement is possible. Experimentally, the sensor was operated in an “isothermal-voltage” mode to identify the frequency regime within which the measurement of the thermal conductivity of representative samples was possible after suitable calibration of the system.