Substrate independent oriented 2D growth of SnS thin films from sputtering

Highly oriented tin monosulfide (SnS) thin films were formed on a silicon (111), Si (100), and glass substrates by annealing sputtered Sn and SnS precursor in an H₂S environment. Sulfurization of pure tin precursor led to high degree of orientation but rough morphology while the sulfurization of SnS precursor resulted in smooth polycrystalline film but with no particular orientation. To achieve both preferred orientation and smooth film, mixed precursors of elemental Sn and SnS at various proportions are studied. The orientation of the film depended on the sputtered precursor rather than the substrate type on which it was grown. Since the growth was not substrate dependent, there was no in-plane-epitaxy in the film. A strong out-of-plane epitaxy at {010} with a rocking curve full width at half maximum (FWHM) as low as 0.42° was achieved for precursor made from sequential deposition of Sn and SnS in thickness ratio of 1:4. The oriented 2D SnS film obtained using such inexpensive process is highly attractive for applications in solar cells with minimal loss at grain boundaries.