Use of cathodoluminescence microscopy to distinguish semiconducting from metallic phases in high T_c superconductors

We show that semiconducting and insulating metal-oxide phases emit substantially greater luminescence when irradiated with 10-30 keV electrons than metallic, candidate high T_c superconducting phases. The use of a cathodoluminescence (CL) detector in a scanning electron microscope to form high-resolution CL images of Y₂O₃, BaCO₃, Y₂BaCuO₅, oxygen-depleted YBa₂Cu ₃O_7-x(x>0.5), and oxygen-annealed YBa₂Cu₃O_7-x(x∼0) is reported. The spatial resolution obtained in CL micrographs of YBa ₂Cu₃O_7-x is found to be about 0.1 μm when the electron beam current is 190 nA. The use of CL microscopy in combination with energy-dispersive x-ray analysis may be a promising technique for identifying candidate superconducting phases of novel stoichiometry in complex multiphase samples.