Deposition of Ge23Sb7S70 chalcogenide glass films by electrospray

a r t i c l e i n f o Solution-based chalcogenide glass films, traditionally deposited by spin-coating, are attractive for their potential use in chip-based devices operating in the mid-infrared and for ease of nanostructure incorporation. To overcome limitations of spin-coating such as excessive material waste and difficulty for scale-up, this paper introduces electrospray as a film deposition technique for solution-based chalcogenide glasses. Electrospray is shown to produce Ge 23 Sb 7 S 70 films with similar surface quality and optical properties as films deposited by spin-coating. The advantages of electrospray deposition for nanoparticle dispersion, scalable and continuous manufacturing with little material waste, and comparable film quality to spin-coating make electrospray a promising deposition method for practical applications of chalcogenide glass films. Chalcogenide glasses (ChGs) are well-known for their potential use as optical components within chip-based photonic devices when fabricated in thin film form [1–9]. Several techniques of ChG thin film deposition exist and have been previously evaluated for physical property attributes as compared to materials in their parent bulk glass form, as such property variation directly impacts post-fabrication optical quality. These include physical vapor deposition techniques (PVD) such as thermal evaporation (TE) or pulsed laser deposition (PLD) methods which both utilize targets of bulk glass (non-solution based) [10–15]. Additionally, recent efforts to exploit the deposition of glass-loaded solutions onto diverse surfaces have received further attention, such as in the wet processing of the amine-based solutions, which offer the flexibility to integrate other functions through solution mixing [16–18]. Furthermore, since glass type and properties can be tuned to tailor the optical and physical properties of the resulting film, integration with other on-chip optical components is envisioned, including coupling of solution-derived waveguides to quantum cascade lasers [19], inter-band cascade lasers, and detectors as well as to resonators which have been function-alized with polymer films or foams [6]. Each type of ChG film deposition has advantages and disadvantages for specific scenarios. PVD techniques, especially TE, are the most commonly used method when studying planar photonic devices because of their low loss, compared to solution-derived films which contain residual organic solvent [16]. However, TE films can show inhomogeneity due to varying volatilization rates of the constituents at different temperatures [10,20]. The typical solution based processing method is spin-coating, which offers the ability to quickly deposit relatively thick films over large areas. However, spin-coating has several limitations: (i) significant amounts of solution …