Vortex States of Exfoliated Bi2Sr2CaCu2O8+y Thin Films with and without Micro-Hole Array

To investigate vortex states in exfoliated Bi2Sr2CaCu2O8+y high-Tc superconductor with and without micro-hole arrays, the in-plane resistance in the vortex states has been measured. In exploration of vortex-lattice melting transition in pristine films, signs of the transition have been successfully found in the films as thin as a few hundred nm. A comparison of irreversibility lines in both samples indicates that influence of artificial micro holes is masked at low temperatures due to the native residual pinnings.