Analysis of glass forming ability using percolation concept and tunability of physical parameters of a-Ge₁₂Se₇₆-_xAs₁₂Bi_xglassy semiconductors

Abstract

Glass forming ability of lone-pair semiconductors was analyzed for (x = 0, 2, 4, 6, 8, 10) system. Values of lone pair electrons L were calculated using average coordination number of valence electrons. These values were found to decrease, as the system was moving towards the rigid region. L > 3 values showed vitreous state. Deviation of the stoichiometry confirmed the chalcogen-rich region. A linear correlation was found between the mean bond energy and glass transition temperature. Chemical Bond Approach model was applied to calculate the cohesive energy of the system. A linear relationship was found to exist between the cohesive energy and the theoretical band gap, calculated using Shimakawa relation. A decrease in both parameters was explained on the basis of average stabilization energy and electronegativity of the system. The density values were found to increase and may account for higher refractive index of the system. Large Bohr radius of the Bi atom accounted for an increase in the polarizability. Other parameters viz. degree of covalency, packing density, compactness, molar volume, free volume percentage, excess volume and polaron radius were also calculated. An effort was made to correlate the effect of Bi addition to Ge12Se76 - xAs12Bixlone-pair semiconductor on the basis of the structure of the glassy matrix or the connectedness of the material.

Optical Characteristics of Thermally Evaporated Thin a-(Cu2ZnGe)50−xSe50+x Films

“…18,47 The constraints number, N Tot-Con for a vitreous substance arises from: the bond bending constraint, N bb, and bond stretching constraint, N bs . Hence, the overall N Tot-Con equals the sum of these two types, 60,61…”

“…One can notice that the two types of constraints are decreasing, and therefore their sum decreasing also as the Se-content increases. 61 It was observed that the total number of mechanical bond constraints, N Tot-Con decreases from 5.125 to 3.875, as the Average heat of atomization, H s .-Heat or enthalpy of atomization (Hs) is the energy that is needed to dissociate one mole of a certain substance into its constituent atoms. It can also be known as the amount of the required energy to convert an amount of some element in its standard state to a mole of atoms in the gaseous state.…”

Optical and dispersion studies of thin S35-xGe15SnxTe50 films: Assessment of some physical parameters of samples

“…It is found that the value of FM decreases from (+0.083) to (−0.083) with an increase in the Sn-content from 0 to 10%. This reduction in FM values indicates that these glassy S-Ge-Sn-Te compositions will become more rigid when increasing Sn-content[82]. Various workers have also reported similar results[67,[82][83][84].On the other hand, the deviation from stoichiometry, R, can also be determined from the average coordinated number, 〈r 〉 through this equation[67,85]:…”