Preparation of electron-doped La2−xCexCuO4±δ thin films with various Ce doping by dc magnetron sputtering

A series of c-axis oriented electron-doped high-Tc superconducting La2−xCexCuO4 thin films, from heavily underdoped x = 0.06 to heavily overdoped x = 0.19, have been synthesized by dc magnetron sputtering technique on (1 0 0) SrTiO3 substrates. The influence of various fabrication conditions, such as the deposition temperature and the deposition rate, etc., on the quality of the thin films has been scrutinized. We find that the quality of the films is less sensitive to the deposition temperature in the overdoped region than that in the underdoped region. In the phase diagram of Tc(x), the superconducting dome indicates that the optimally doping level is at the point x = 0.105 with the transition temperature Tc0 = 26.5 K. Further more, both the disappearance of the upturn in the ρxx(T) curve at low temperature under H = 10 T and the positive differential Hall coefficient, RH′=dρxy/dH, are observed around x = 0.15, implying a possible rearrangement of Fermi surface at this doping level.