Effect of tellurium substitution in Sn

The as-prepared samples of Sn10Sb20Se$_{70-X}$ TeX chalcogenide system were amorphous as evidenced by X-ray diffraction and Differential scanning calorimetry studies. The different crystalline phases emerged in annealed Sn10Sb20Se$_{70-X}$ TeX samples have been identified. Glass transition temperature Tg of the as-prepared samples decreases sharply with tellurium substitution upto 2 at% and then it starts increasing upto 10 at% and decreases again on further substitution of tellurium. The change in glass transition temperature Tg has been explained based on bond formation energy of different heteropolar bonds and crystalline phases obtained in the annealed samples with different tellurium contents

Phase segregation in Pb:GeSbTe chalcogenide system

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

Phase transformation in Pb:GeSbTe chalcogenide films

A comprehensive analysis on the amorphous to crystalline phase transformation in Pb:GeSbTe chalcogenide alloy has been discussed. The structure identified with X-ray measurements has been discussed in relation to thermal analysis carried out on bulk samples. Optical constants have been calculated in the 350 to 800 nm wavelength range, using Fresnel's equation. The effect of Pb substitution on the optical contrast in terms of change in reflectivity and optical parameters (viz. refractive index, extinction coefficient) has been discussed. Marginal decrease in the optical contrast has been observed with a small increase in Pb content, which is effective to maintain the sufficient signal to noise ratio for optical phase-change storage