Ge and As x-ray absorption fine structure spectroscopic study of homopolar bonding, chemical order, and topology in Ge-As-S chalcogenide glasses

X-ray photoelectron spectra of Ge-As-Te glasses

“…Thus, the number of GeTe 4/2 pyramidal units decrease and Ge-Ge-containing units corresponding to the high binding energy doublets, appear in Ge 10 As 45 Te 45 glasses. In fact, the existence of homopolar Ge-Ge or Ge-As bonds is in agreement with those reported in Raman analysis of Ge x As 2x Te 100-3x , 28 x-ray absorption fine structure spectroscopic studies of Ge-As-S 29,30 and XPS studies of Ge-As-Se glasses, 21,32 where such homopolar bonds appear in the chalcogen-poor glasses. Moreover, the amount of GeTe 4/2 structural units decreases but that of Ge-Ge-containing units increases with decreasing Te content.…”

Atomic structure and chemical order in binary Ge–Te and As–Te glasses: A Te K-edge X-ray absorption fine structure spectroscopic study

“…The non-linear variation in physical properties with composition in chalcogenide glasses has been variously ascribed to rigidity percolation, topological phase transition and chemical bonding effects [10,12,13,[16][17][18][19][20]. According to the percolation and topological models, the physical properties of chalcogenide glasses are expected to be controlled by the average coordination number <r> rather than the actual chemical composition of the glass [16][17][18][19][20].…”

“…On the other hand, structural models based on chemical ordering have correlated physical property variations with the formation of Ge/As-Ge/As (S, Se-S, Se) homopolar bonds in chalcogen -deficient (excess) non-stoichiometric glasses, especially in binary Ge-S, Se or As-S, Se systems [21,22]. Recent structural studies with Raman spectroscopy and Ge and As K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) have indicated a more complex picture of structure-property relationships in ternary Ge-As-S glasses where homopolar and heteropolar bonds are significantly different [10,13]. Raman spectroscopic results have shown conclusively that As-As homopolar bonding results in the formation of molecular As 4 S 3 units in S-deficient Ge-As-S glasses, especially in As-rich compositions [13].…”

“…Recently there has been a renewed surge of interest in telluride glasses as these materials exhibit interesting phenomena such as electrical switching and optical phase change recording [6,7]. As a result, the structure-property relationships in chalcogenide glasses have received a great deal of research attention in recent years [8][9][10][11][12][13][14][15].…”

Short range order in Ge–As–Se glasses

“…Various experimental studies revealed that chemical ordering is very pronounced in the Ge-As-S system as well. Sen et al investigated the structure of Ge x As y S 1-x-y glasses with x:y = 1:2, 1:1, and 2.5:1 over a wide-ranging S content [40]. It was found that upon decreasing the S content first As-As bonds appear, while Ge takes part in metal-metal bonds only in strongly S-poor compositions.…”