Thermal studies of the effect of thallium in ternary Ge-Te-Tl chalcogenide glasses
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Thermal studies of the effect of thallium in ternary GeTe-Tl chalcogenide glasses Mohammad Mahbubur Rahman1,3, K. Rukmani1,*
, Rajam Sekar2, and S. Asokan2
1
Department of Physics, Bangalore University, Bangalore 560056, India Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India 3 Present address: Department of Physics, International University of Business Agriculture and Technology (IUBAT), Dhaka-1230, Bangladesh 2
Received: 23 August 2020
ABSTRACT
Accepted: 9 November 2020
Alternating differential scanning calorimetric (ADSC) studies have been carried out on bulk Ge17Te83-xTlx glasses over a wide range of compositions (0 B x B 13), to estimate the thermal parameters and also to understand the effect of thallium addition on the non-isothermal crystallization process. It is found that glass transition temperature (Tg) decreases with increasing thallium concentration, indicating decrease in network connectivity with thallium addition. The decrease in Tg is large in the composition range 0 B x B 6 and much less for compositions x C 7. The observed composition dependence of Tg is similar to the variation in switching voltages with composition and is in close agreement with the variation in the average bond energy. Further, two crystallization temperatures (Tc1 and Tc2) have been observed in Ge17Te83-xTlx glasses, in the composition range 2 B x B 10, which indicates that glasses in this range are phase separated. As these glasses are tellurium rich, it is probable that the regions formed by Te- chains crystallize first and the rest of the matrix crystallizes later. The change in enthalpy due to non-reversing part of the heat flow is very small and fairly constant over the entire range of glasses studied. This indicates that structural re-organization is easy in this system which agrees well with the memory type electrical switching observed in these samples.
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Springer Science+Business
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1 Introduction Electrical switching in chalcogenide glasses can be of two types, such as memory type switching and threshold type switching, where the former is irreversible and the latter is reversible when the
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https://doi.org/10.1007/s10854-020-04863-w
switching voltage is removed. Materials exhibiting memory type switching which involves transformation of the glass from amorphous to crystalline state can be used as phase change memories (PCMs) and are found to be possible replacements for conventional flash non-volatile random access memories
J Mater Sci: Mater Electron
(NVRAMS) [1–4]. The seeds of this commercial application were sown with the observation of two resistance states in MOS2 and later the discovery of switching in As-Te-Br or I semiconducting glasses [5]. However, the appreciation of the application potential and the need to understand the details of the behavior of such materials really began with the classic paper of Ovshinsky [6]. There have been several
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