Optimized growth conditions of epitaxial SnSe films grown by pulsed laser deposition

We have grown epitaxial tin monoselenide (SnSe) films on MgO or SrTiO₃ (STO) substrates by pulsed laser deposition (PLD) at T _s = 473 or 573 K, and investigated the optimized growth condition in terms of crystal orientation, crystallinity, and electrical resistivity. For the PLD procedure, a SnSe _x (x = 1.0-1.6) target containing excess Se was used to compensate for the vaporization of Se. The crystal orientation and crystallinity of the SnSe films changed depending on the growth conditions, and the magnitude of the electrical resistivity ρ of the films was closely related to the crystalline nature. The SnSe film grown on the MgO substrate at T _s = 573 K using the target with x = 1.4 was the most highly a-axis-oriented and highly crystalized among all of the films investigated in this study. However, the ρ of the film in the bc-plane was about one order of magnitude larger than those of the reported single crystal and the a-axis-oriented crystalline sample fabricated by spark plasma sintering. This larger ρ was suggested to result from the lattice mismatch and/or a small amount of nonstoichiometry in the film.