  The superconductivity phase diagrams of electron doped cuprates of the form
R(2-x)CexCuO4 (with R= La, Pr, Nd, Sm, and Eu) have been determined for cerium
compositions 0 < x < 0.36 in a consistent series of epitaxial thin films grown
by reactive molecular beam epitaxy (MBE). The use of epitaxial thin films
allows the growth of materials away from thermodynamical equilibrium expanding
the accessible phase space beyond the availability of bulk material. The
superconducting phase space systematically increases with the rare earth ionic
size. The doping concentration where the maximal transition temperature occurs
in La(2-x)CexCuO4 is considerably shifted to lower doping (x ~ 0.09) compared
to La(2-x)SrxCuO4 (x ~ 0.15). At the same time, the width of the
superconducting region is broadened.
