  Two-dimensional (2D) materials provide an ideal platform to explore novel
superconducting behavior including Ising superconductivity, topological
superconductivity and Majorana bound states in different 2D stoichiometric Ta-,
Nb-, and Fe-based crystals. However, tuning the element content in 2D compounds
for regulating their superconductivity has not been realized. In this work, we
report the synthesis of high quality Fe1+yTe with tunable Fe content by
chemical vapor deposition (CVD). The quality and composition of Fe1+yTe are
characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and
scanning transmission electron microscopy (STEM). The superconducting behavior
of Fe1+yTe crystals with varying Fe contents is observed. The superconducting
transition of selected Fe1.13Te sample is sharp ({\Delta}Tc = 1 K), while
Fe1.43Te with a high-Fe content shows a relative broad superconducting
transition ({\Delta}Tc = 2.6 K) at zero magnetic field. Significantly, the
conspicuous vortex flow and a transition from a 3D vortex liquid state to a 2D
vortex liquid state is observed in Fe1.43Te sample. Our work highlights the
tunability of the superconducting properties of Fe1+yTe and sheds light on the
vortex dynamics in Fe-based superconductors, which facilitates us to understand
the intrinsic mechanisms of high-temperature superconductivity.
