Improving Processing and Coating Protocol to Promote Crystal Formation and Optical Function in Thin GeSbSeTe Films

Thin optical films are created by dissolving glass powder into an amine, like ethylene-diamine (EDA) and ethanethiol, applying a thin layer of this solution onto a glass or silicon substrate and then heating the substrate to remove excess solvent. The current method used to create glass films composed of germanium (Ge), antimony (Sb), selenium (Se), and tellurium (Te) (GSST) contains a high amount of Te crystals and crystal growth post heat treatments. Working with our partners at University of Central Florida, a way to reduce the unwanted crystal formation was explored using a few modifications. The first modification involves altering the composition of the bulk glass that will be dissolved to create the solution. A second modification requires altering the ratio of thiol to EDA used to dissolve the glass to create the solution. A third modification requires the solutions to be filtered using a syringe and a fine filter, instead of using a sieve only. FTIR measurements were made to determine the transmission and to see the amount, if any, of EDA or Thiol residue left in the film. Raman spectroscopy, post-bake transparency, and laser irradiation were used to determine the crystallinity of Te in the films. The goal of this research is to improve the current processing methods to create dip coated films and to reduce the unwanted Te crystal formation and promote 4 – crystal phase growth which will, in turn, be used as a phase change material. This phase change material will exhibit refractive index changes upon light or thermal radiation