Solution processed Ge₂₀Sb₅S₇₅ thin films: the effect of solution concentration and multiple layers stacking

Abstract

Ge 20 Sb 5 S 75 thin films with high chemical resistance to aliphatic amines were deposited from solutions of various glass concentrations (0.015-0.09 g of grinded glass material/ml of n-butylamine) by the spin-coating technique. As-prepared and annealed thin films were analyzed by spectroscopic ellipsometry and EDS (energy-dispersive X-ray spectroscopy). Results proved that the refractive index of thin films was not affected by the solution concentration (within studied range), and the studied optical properties of deposited samples were homogenous in their volume. The Ge 20 Sb 5 S 75 solution of the highest concentration (0.09 g/ml) was chosen for deposition of thicker chalcogenide glass material using multiply deposition/thermal stabilization procedure. Prepared multilayers proved to have good optical quality and homogenous chemical resistance through the whole thickness. No interfaces between layers were observed from etching kinetics and SEM scans. Thus, the results confirmed that multiple layers stacking procedure is suitable for deposition of thick homogenous Ge 20 Sb 5 S 75 thin films.

Preparation of quaternary solution processed chalcogenide thin films using mixtures of separate As40S60 and Ge20Sb5S75 glass solutions

“…We can also speculate that the significantly smaller sizes of Ge20Sb5S75 glass dissolution products also significantly decrease the dissolution rate of studied samples. Obtained results of high chemical resistance of annealed Ge20Sb5S75 are in a good agreement with our previous studies on Ge-Sb-S thin films [22,25].…”

“…Significant overstoichiometry of sulfur in Ge20Sb5S75 composition is manifested by presence of bands at 150, 219 and 475 cm -1 belonging to sulfur rings S8 [39,40] and sulfur chains S-S at 490 cm -1 [39,40]. Three additional bands at 142, 190 and 455 cm -1 can be attributed to the vibrations of ionic dissolution products in form of AAGS salts [22,25,42]. Similarly to the As40S60 thin films, the annealing induces decomposition of AAGS salts and consequently structural polymerization.…”

“…Moreover, the As40S60 bulk glass and thin films were already thoroughly studied and bulk glass is commercially available as AMTIR 6, IRG 27 or IRRADIANCE TM Classic-1. The annealed Ge20Sb5S75 solution processed thin films showed very high chemical stability that allows thickness tuning using layer stacking [25] and proved to be suitable for preparation of solution processed thin films with high optical quality. In this paper, we show the influence of composition and thermal post-deposition treatment on structure, thickness, surface roughness, organic residual content, optical properties and chemical resistance of spin-coated thin films prepared by mixing of two different glass solutions.…”

Solution processed multi-layered thin films of Ge20Sb5S75 and Ge20Sb5Se75 chalcogenide glasses

“…Figure 2 gives evidence that both nitrogen and oxygen contents decrease significantly with increasing annealing temperature, which proves release of the organic residua from the structure of the thin film. It is worth mentioning that hard-baked thin films show significantly lower content of nitrogen in comparison to sulfur-based thin films of analogous composition Ge 20 Sb 5 S 75 37 .

Figure 2 Annealing temperature dependence of the N/Ge and O/Ge elemental ratios in the thin films.

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“…The optical properties of prepared thin films were studied in dependence on the annealing temperature in order to study the thermoinduced compositional and structural changes occurring in the thin film during annealing. Our previous work on Ge 20 Sb 5 S 75 amorphous thin films revealed significant chemical resistance of hard-baked thin films allowing direct repeated depositions of the glass solution on the thin film to reproducibly prepare thicker samples 37 . The hard-baked Ge 20 Sb 5 Se 75 thin films studied in the presented paper showed remarkably high chemical resistance as well, which in combination with high refractive index allowed their use for production multilayered photonic materials.…”