  We found that the electronic transport property of SnSe single crystals was
sensitive to oxygen content. Semiconducting SnSe single crystals were obtained
by using Sn of grain form as a starting material while powder Sn resulted in
metallic SnSe. X-ray photoelectron spectroscopy analysis revealed that the
surfaces of raw Sn were oxidized, where the volume fraction was relatively low
in grain Sn. This demonstrates that contamination of oxygen causes metallic
behavior in grown SnSe single crystals.
