Amorphous To Amorphous Insulator-Metal Transition In Gese3:Ag Glasses

We study an insulator-metal transition in a ternary chalcogenide glass (GeSe3)(1-x)Ag-x for x = 0.15 and 0.25. The conducting phase of the glass is obtained by using gap sculpting [Prasai et al., Sci. Rep. 5, 15522 (2015)] and it is observed that the metallic and insulating phases have nearly identical density functional energies but have a conductivity contrast of similar to 10(8). As such, we demonstrate an example of polyamorphism for which energetically close phases exhibit dramatically different optical properties. The transition from insulator to metal involves growth of an Ag-rich phase accompanied by a depletion of tetrahedrally bonded Ge(Se-1/2)(4) in the host network. The relative fraction of the amorphous Ag2Se phase and GeSe2 phase is shown to be a critical determinant of dc conductivity.