Magnetic penetration depth measurements of Pr2-xCexCuO4-δ films on buffered substrates:: Evidence for a nodeless gap -: art. no. 087001

We report measurements of the inverse squared magnetic penetration depth, lambda(-2)(T), in Pr2-xCexCuO4-delta (0.115less than or equal toxless than or equal to0.152) superconducting films grown on SrTiO3 (001) substrates coated with a buffer layer of insulating Pr2CuO4. lambda(-2)(0), T-c, and normal-state resistivities of these films indicate that they are clean and homogeneous. Over a wide range of Ce doping, 0.124less than or equal toxless than or equal to0.144, lambda(-2)(T) at low T is flat: it changes by less than 0.15% over a factor of 3 change in T, indicating a gap in the superconducting density of states. Fits to the first 5% decrease in lambda(-2)(T) produce values of the minimum superconducting gap in the range of 0.29less than or equal toDelta(min)/k(B)T(c)less than or equal to1.01.