Mechanism of the dissolution of As–S chalcogenide glass in n-butylamine and its influence on the structure of spin coated layers

Abstract

Chalcogenide glass thin layers are useful to many practical applications especially for the fabrication of infrared (IR) optical elements. In comparison to the conventional vacuum deposition methods of their preparation, recently chemical methods such as spin coating are gaining attention. They involve dissolution of the source bulk glass in appropriate solvent and then depositing its thin layer. Chemical processes occurring during the glass dissolution and thin layer deposition determine the physicochemical properties of deposited thin layers. The structure of chalcogenide bulk glasses (As x S 100-x , where 30  x  40) and their solutions in n-butylamine has been studied in this work by Raman spectroscopy. From the composition and time dependence of Raman spectra of solutions the mechanism of arsenic-sulfur glass dissolution involving the reaction of aliphatic amine solvent with homopolar S-S bonds is proposed and the presence of alkyl ammonium arsenic sulfide salts in thin layers is established.

Structure and properties of spin-coated Ge_25S_75 chalcogenide thin films

“…The S8 ring bands at 151, 218 and 475 cm -1 are also present in measured spectrum, but their intensity is higher than in the Raman spectrum of source bulk glass. The bands at 2800 -3000 cm -1 prove that the deposited thin films contain also residual BA molecules [16]. Three additional bands at 144, 191 and 455 cm -1 can be identified in Raman spectrum of as-prepared sample.…”

“…9) proved, that the chemical stability gradually increases with increasing annealing temperature. According to the literature [16,17] the annealing above the organic salts decomposition temperature also induces significant structural polymerization resulting in more compact thin films. As the organic AAGS salt decomposition temperature was based on SE and EDS measurements expected to be above 120 °C, the chemical stabilization effect of annealing is evident.…”

“…Spincoating and dip-coating deposition methods are frequently used for ChG thin films deposition [12][13][14][15][16][17], but these techniques are suitable only for basic material research and small scale production. Well known and managed printing [18] and coating [19] techniques allowing continuous deposition are gaining attention for large scale production purposes.…”

“…Major disadvantage of solution based deposition methods are the residual amount of solvent remaining in the thin film's structure. But its content can be significantly lowered by proper annealing [12,13,16].…”

“…Thin films deposited by solution based techniques have been widely studied on arsenicbased ChGs [12][13][14][15][16][17], which limits their wide-spread application due to the arsenic toxicity. Germanium-based spin-coated thin films of Ge23Sb7S70 glass composition were successfully prepared [20], but further study of other germanium-based systems is needed to obtain plurality of different non-toxic optical materials prepared by solution based deposition techniques.…”