  We present phase-sensitive evidence that the electron-doped cuprates
Nd1.85Ce0.15CuO4-y (NCCO) and Pr1.85Ce0.15CuO4-y (PCCO) have d-wave pairing
symmetry. This evidence was obtained by observing the half-flux quantum effect,
using a scanning SQUID microscope, in c-axis oriented films of NCCO or PCCO
epitaxially grown on tricrystal [100] SrTiO3 substrates designed to be
frustrated for a d(x2-y2) order parameter. Samples with two other
configurations, designed to b unfrustrated for a d-wave superconductor, do not
show the half-flux quantum effect.
