Defects in a Disordered World: The Structure of GlassyGeSe2

Abstract

The full set of partial structure factors for the prototypical network glass GeSe2 was measured using the method of isotopic substitution in neutron diffraction. The basic building block of the network is the Ge(Se(1/2))(4) tetrahedron in which 34(5)% of the Ge reside in edge-sharing configurations. The intrinsic chemical order of the glass is, however, broken with a maximum of 25(5)% Ge and 20(5)% Se being involved in homopolar bonds at distances of 2.42(2) and 2.32(2) A, respectively.

Short range order in Ge–As–Se glasses

“…N i , the total coordination number of the ith component is defined as the sum of N ij , the average number of j type neighbors around i type atoms. We note here that the validity of the '8-N' rule in IV-V-VI glasses have been confirmed by several studies [35][36][37][38]. The above coordination constraints were fulfilled generally by ~95% of the atoms.…”

Reverse Monte Carlo simulations and Raman scattering of an amorphous GeSe4 alloy produced by mechanical alloying

“…The first peak of G RMC Se-Se (r) function is located at 2.33Å, and it corresponds to a coordination number N Se-Se = 1.71, which is much higher than that obtained for the MQ-GeSe 2 samples (N Se-Se = 0.20) 3,5 . This suggests that some of the tetrahedral units are connected by Se "bridges", forming sequences such as Ge-Se-Se-Se-Ge.…”

“…As described in Ref. 5, this alloy is formed by CS and ES units with heteropolar bonds but there are homopolar bonds in very small quantities. It should be noted, however, that almost all available data about a-Ge x Se 1−x alloys were determined for MQ samples, and the preparation method can affect the SRO and IRO.…”

Building block modeling technique: Application to ternary chalcogenide glasses g-Ge2As4SeCai1, Zhang2, Drabold3 2011Phys. Rev. B

“…However, the lack of translational periodicity makes it hard to predict the microscopic structure of these glasses. Experimental results indicate that chemical order is broken and homopolar bonds are observed in chalcogenide glasses [4][5][6] . To further understand the topology and its role in determining optoelectronic and electronic properties, realistic atomistic models of these glasses are required.…”