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

Abstract

We show that semiconducting and insulating metal-oxide phases emit substantially greater luminescence when irradiated with 10–30 keV electrons than metallic, candidate high Tc 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 YBa2Cu3O7−x(x>0.5), and oxygen-annealed YBa2Cu3O7−x(x∼0) is reported. The spatial resolution obtained in CL micrographs of YBa2Cu3O7−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.

Homogeneity assessment of YBa2Cu3O7−x single crystals by cathodoluminescence microscopy

“…More recently, CL in the scanning electron microscope ͑SEM͒ has been used to characterize HTSC ceramics. Miller et al 7 observed that insulating phases in YBa 2 Cu 3 O 7Ϫx emit higher CL signals than nominally metallic phases, and other CL microscopy works indicated the relationship between certain luminescence features and oxygen-depleted zones in YBa 2 Cu 3 O 7Ϫx . [8][9][10][11] In particular a 2.3 eV emission band was related to centers involving oxygen vacancies.…”

Study of structural changes in YBa2Cu3O7−x by cathodoluminescence in the scanning electron microscope

“…In Ref. 5 it was found that the total CL emission from oxygen-depleted YBa20.l307 x(x > 0.5) is consistently higher than that emitted by oxygen-annealed YBa2Cu307 _ xCx ~ 0). The role of oxygen in the luminescence emission of high Tc superconductors has also been pointed out in Ref.…”

Cathodoluminescence microscopy of superconducting and non-superconducting Tl2Ba2CuO6+δ polycrystals

“…Since the mentioned treatments cause a variation in the oxygen stoichiometry or distribution, the possibility that the 540 nm luminescence is related to mechanisms in the oxygen sub-lattice has been investigated. Miller et al [14] reported an increase of CL signal in oxygen-depleted zones of YBCO produced by electron irradiation. Similar effects were reported in Refs.…”