Study of amorphous Sn–Se–Bi–Te semiconducting materials at an average coordination number <r>= 2.4

Improvement in spectral range of Sb 2 Se 3 absorption layer on Bi addition

“…) where m i is the atomic mass fraction and D i is the density of the i th atom [32]. The values of fundamental densities for Sb is 6.697 g cm −3 , Se is 4.28 g cm −3 and Bi is 8.498 g cm −3 [33,36]. The values of the density calculated for samples on Bi incorporation to Sb 2 Se 3 system show an increase with increase in Bi content (table 2).…”

“…Bi where, a b ¡ , , and are the atomic fractions and N Sb , N Se and N Bi are the coordination numbers for Sb, Se, Bi respectively. The values of coordination number for Sb, Se and Bi are 3, 2, and 3 respectively [32,33]. For 〈Z〉 less than 2.4 system is under coordinated region, rigid regions are unconnected and isolated, for 〈Z〉 equal to 2.4 system is an ideal and for 〈Z〉 greater than 2.4, the system is over coordinated regions and stressed rigid [32].…”

“…When the coordination of atoms takes place in a system, then various types of constraints act on the system. According to the theory of constraints, there are two forms of near-neighbour bonding forces in covalent solids: bond stretching (N α ) and bond bending (N β ) [33]. Bond stretching constraint appears due to linear forces, and bond bending constraint appears due to the angular forces.…”

“…where a, b, and c represent the volume fractions and the energy gap of these atoms for computing the E g values are 0.1 eV, 1.74 eV, 0.1 eV for Sb, Se, Bi respectively [32,33]. Shaaban et al also observed an increase in the density with decrease in optical energy gap on replacing Se by Sb in Sb x Se 100-x system [44].…”