Infrared Reflection and Raman Scattering Studies of the Vibrational Properties and Structure of As2S3Gex Glasses

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Abstract
Infrared reflection and Raman spectra of As2S3Gex (0 ≦ x ≦ 35 at%) glasses are studied. The spectra are explained in terms of vibrational modes of atomic building blocks the investigated glasses are composed of. Particularly, the vibrational properties of the As2S3Gex (x < 4 at%) glasses are due to internal vibrations of AsS3/2 pyramidal and weakly As‐rich AsrSs (r/s ⪅ 1) building blocks. The number of GeS4/2 tetrahedral building blocks is very small, therefore, these structures do not noticeably affect the infrared reflection and Raman spectra of the considered glasses. The vibrational properties of the As2S3Gex. (4 ⪅ x ⪅ 14 at%) samples are dominantly affected by vibrations of As‐rich AsrSs (r/s ≈ 1), GeS4/2 tetrahedral, and AsS3/2 pyramidal building blocks. (The number of AsS3/2 pyramidal building blocks approaches zero in samples with Ge contents above about 10 at%.) Raman spectra indicate that samples with Ge contents between about 4 and 12.5 at% contain realgar‐like microcrystals. The vibrational properties of the As2S3Gex (x > 14 at%) glasses mainly are caused by vibrational modes of GeS4/2 tetrahedral and strongly As‐rich AsrSs (r/s ⪆ 1.3; including AsAs3/3) building blocks. Stretching vibrations of AsAs bonds of these strongly As‐rich AsrSs building blocks are indicated in the Raman spectra of the considered glasses. In glasses with x ⪆ 23 at% Ge content the number of AsS bonds becomes zero, therefore weakly Ge‐rich GeuSv (u/v ⪆ 0.67) building blocks are formed.