Exploring Electronic Properties of SnS Cubic Phase

SnS is an earth-abundant semiconductor with an orthorhombic crystallographic structure that possesses near-optimal direct band-gap of 1.3eV, high absorption coefficient and high density of charge carriers. Consequently, this material is widely used in environmentally-friendly applications, such as photovoltaic and photocatalytic devices for clean and renewable energy production. Recently, a new cubic binary phase of SnS was discovered in our group – a crystallographic structure of this material that was hitherto unknown. Preliminary research demonstrated unique properties, including exceptionally high lattice parameter (11.6Å), increased band gap of 1.5-1.7eV, mechanical stability and p-type conductivity of the cubic SnS phase. In the current work, we explored the electronic properties of the cubic SnS and compared them with those of its orthorhombic-phase counterpart. First, we deposited orthorhombic and cubic SnS thin films on Fluorine doped Tin Oxide (FTO) and p-Si substrates. This was attained using the chemical bath deposition method, which is an inexpensive, simple and environment-friendly growth technique. We characterized the structure of the resulting films using Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy and X-ray Diffraction. After achieving a complete and adherent coverage of the substrate in glove box environment, preliminary contact potential difference (CPD) measurements by the Kelvin probe method, aimed at characterizing the film`s work function, showed unexpectedly low values suggesting the presence of tin oxide on the surfaces of both of the films. Ultraviolet Photoelectron Spectroscopy, aimed at characterizing the ionization potential, showed similar trends. X-ray Photoelectron Spectroscopy was then used to confirm this. Future work will include sputtering (milling) of the surface, in order to remove the oxide layer and to characterize the properties of the SnS phases.