Evolution of the resistivity of single-layer Bi2Sr1.6La0.4CuOy thin films with doping and phase diagram

The temperature dependence of the in-plane resistivity rho (T) is measured on epitaxial c-axis oriented single-layer Bi2Sr1.6La0.4CuOgamma thin films at various oxygen concentrations. By successive annealing treatments, the o xygen content of the same film is changed from maximally overdoped to stron gly underdoped non-superconducting state, passing through the optimal state with T-cmax = 30 K. The underdoped states show a downturn of the resistivi ty from the high T-linear behavior below a characteristic temperature T*, s ignature of the pseudogap effect. T*: appears near optimally doped state an d increases sharply with decreasing carrier concentration. Two other charac teristic temperatures are observed in rho (T) for underdoped states: the te mperature T-I of the inflection point in rho (T) (T-I similar to 0.5T*) and the temperature T-M corresponding to the onset of localization effects. A phase diagram T versus doping is established. (C) 2001 Elsevier Science B.V . All rights reserved.