In this study, four different samples of Se60Ge40-xBix chalcogenides glasses were synthesized by heating the melt for 18 h in vacuum Pyrex ampoules (under a 10-4 Torre vacuum), each with a different concentration (x = 0, 10, 15, and 20) of high purity starting materials. The results of direct current (DC) electrical conductivity measurements against a 1,000/T plot for all chalcogenide samples revealed two linear areas at medium and high temperatures, each with a different slope and with different activation energies (E1 and E2). In other words, these samples contain two electrical conduction mechanisms: a localized conduction at middle temperatures and extended conduction at high temperatures. The results showed the local and extended state parameters changed due to the effective partial substitution of germanium by bismuth. The density of extended states N(Eext) and localized states N(Eloc) as a function of bismuth concentration was used to gauge this effect. While the density of the localized states decreased from 1.6 × 1014 to 4.2 × 1012 (ev-1 cm-3) as the bismuth concentration increased from 0 to 15, the density of the extended states generally increased from 3.552 × 1021 to 5.86 × 1021 (ev-1 cm-3), indicating a reduction in the mullet’s randomness. This makes these alloys more widely useful in electronic applications due to the decrease in the cost of manufacturing.

1. Introduction
2. Experimental Procedure
    2.1. The theory part
    2.2. The process of electrical conduction betweenextended states
    2.3. The process of electrical conduction betweenlocalized states
    2.4. Electric conduction (at Fermi level)
3. Results and Discussion
4. Conclusion
References
Author Information

• Kareem Ali Jasim(Department of Physics, College of Education for Pure Sciences ibn Al-Haitham, University of Baghdad, Baghdad, 10001, Iraq) Corresponding author
• Ebtisam Mohammed Taqi Salman(Department of Physics, College of Education for Pure Sciences ibn Al-Haitham, University of Baghdad, Baghdad, 10001, Iraq)
• Shaymaa Hashim Aneed(Department of Physics, College of Education for Pure Sciences ibn Al-Haitham, University of Baghdad, Baghdad, 10001, Iraq)
• Haider Sahi Hussein(General Directorate of Karbala Education, Karbala 56001, Iraq)