  Among iron based superconductors, the layered iron chalcogenide Fe(Te1-xSex)
is structurally the simplest and has attracted considerable attentions. It has
been speculated from bulk studies that nanoscale inhomogeneous
superconductivity may inherently exist in this system. However, this has not
been directly observed from nanoscale transport measurements. In this work,
through simple micromechanical exfoliation and high precision low-energy ion
milling thinning, we prepared Fe(Te0.5Se0.5) nano-flake with various thickness
and systematically studied the correlation between the thickness and
superconducting phase transition. Our result revealed a systematic evolution of
superconducting transition with thickness. When the thickness of Fe(Te0.5Se0.5)
flake is reduced down to 12nm, i.e. the characteristic length of Te/Se
fluctuation, the superconducting current path and the metallicity of normal
state in Fe(Te0.5Se0.5) atomic sheets is suppressed. This observation provides
the first direct transport evidence for the nano-scale inhomogeneous nature of
superconductivity in Fe(Te1-xSex).
