  The parameters influencing the band gap of tin sulphide thin nano-crystalline
films have been investigated. Both grain size and lattice parameters are known
to influence the band gap. The present study initially investigates each
contribution individually. The experimentally determined dependency on lattice
parameter is verified by theoretical calculations. We also suggest how to treat
the variation of band gap as a two variable problem. The results allow us to
show dependency of effective mass (reduced) on lattice unit volume.
