We report on transport properties of the topological insulator single crystal $Sb2Te3$ nanoflakes with thickness about from 7 to 50nm. A steep drop of resistance is appeared near $3K$ in the ultrathin $Sb2Te3$ nanoflakes, manifesting a superconducting transition.The magnetic field induced superconductor insulator transition of disordered 2D superconductor system is observed in the nanoflakes.The results show that the existence of certain optimum degree of disorder is a necessary condition for emergence of superconductivity.Temperature dependence of magneto-resistance shows a consecutive transformation of weak antilocalization cusp into the superconducting transition at low field when $B < BC$.
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