  We have synthesized polycrystalline samples and single crystals of
Fe(Te1-xSx)y, and characterized their properties. Our results show that the
solid solution of S in this system is limited, < 30%. We observed
superconductivity at ~ 9 K in both polycrystalline samples Fe(Te1-xSx)y with 0<
x <= 0.3 and 0.86 <= y <= 1.0, and single crystals with the composition
Fe(Te0.9S0.1)0.91, consistent with the recent report of Tc ~ 10 K
superconductivity in the FeTe1-xSx polycrystalline samples with x = 0.1 and
0.2. Furthermore, our systematic studies show that the superconducting
properties of this system sensitively depend on excess Fe at interstitial sites
and that the excess Fe suppresses superconductivity. Another important
observation from our studies is the coexistence of the superconducting phase
and antiferromagnetism. Our analyses suggest that this phase coexistence may be
associated with the random distribution of excess Fe and possibly occurs in the
form of electronic inhomogeneity.
