Sn_xS_y MSELD stack thin films: Processing, characteristics and devices for photonic applications

摘要

SnxSy varied stoichiometric stack thin films (S1, S2, S3) were obtained using multisource sequential elemental layer deposition (MSELD) technique on annealing. The composition of the SnxSy thin films were varied by supplementing sulphur on predeposited Sn : S (1 : 1) constituents using MSELD technique. Present investigation exhibit formation dynamics of MSEL deposited SnxSy films by condensed state reaction on varying composition and annealing temperatures (473 K, 523 K and 623 K) under constant vacuum. The deposited films exhibit composition variation ranging from 0.5 (S/Sn) to 1.5 (S/Sn) and results into the formation of varied alloy SnxSy phases. These varied alloy phase formation achieved due to diffusion of sulphur atoms on annealing of the varied composition MSELD stack. These variations in phases and composition on annealing allow bandgap tuning from 1.1 eV to 2.1 eV with changed absorption coefficient over the Vis-NIR (Visible - Near infrared) region. The stack films (S1, S2, S3) exhibit p-type electrical resistivity with promising electrical parameters viz. lower resistivity (62-309 Omega cm), mobility (3.1-17 cm(2)/V s) and carrier concentration (similar to 10(14)-10(15) cm(-3)) on annealing at 523 K for their use in photovoltaic (PV) technology. To achieve photonic and electronic devices, the schottky (FTO/SnxSy(S2)/Ag) diodes of varied composition and heterojunction (FTO/SnxSy(S2)-CdS/Ag) were tested and exhibit nearly ideal behaviour (ideality factor 1.1) for S2 films. In summary, the results demonstrates peculiar characteristics of the SnxSy material system as nano dimension electrical switches, tunable narrow and wide direct bandgaps with higher absorption capabilities in Vis - NIR region for their use in PV technology.