Localization processes near the superconductor–insulator transition in Bi2Sr2 − xLaxCuOy nanoscale thin films

Thin film Bi2Sr2 − xLaxCuOy (x = 0.6) was deposited onto SrTiO3 by using DC magnetron sputtering. The structural characterization was carried by X-ray diffraction and the transport properties were carried by resistivity and Hall Effect measurements. The underdoped system near superconductor–insulator transition (SIT) was performed by partial substitution of Sr with x = 0.6 La. By varying the oxygen content in very small amounts through a vacuum anneal process, a highly precise hole-doping of thin film was obtained and the same film is changed from initial superconducting state to strongly insulating underdoped state. More than 14 doping states in the vicinity of SIT were performed and studied by electrical resistivity as function of temperature. The thermally activated behavior, log (1/T) behavior or electrical resistivity and VRH localization processes were evidenced function of doping and temperature.