  Sulfur-doped SnSe single crystal was successfully synthesized using a melt
and slow-cooling method. The chemical composition and valence state of the
obtained sample were analyzed by X-ray photoelectron spectroscopy. The pressure
range of a diamond anvil cell with boron-doped diamond electrodes was upgraded
to 104 GPa using nano-polycrystalline diamond anvil to investigate a pressure
effect for the sample. Electrical resistivity measurements of sulfur-doped SnSe
single crystal showed the insulator-metal-superconductor transition by applying
high pressure up to 75.9 GPa.
