HIGH-RESOLUTION AND ANALYTICAL ELECTRON-MICROSCOPY OF HGBA2CUO4+DELTA - A NEW COPPER-OXIDE SUPERCONDUCTOR

High-resolution and analytical electron microscopy (HREM and AEM, respectively) techniques have been utilized to probe the submicroscopic details of crystallography, chemistry and electronic structure of HgBa2CuO4+delta, a recently discovered single--layer copper-oxide superconductor. Core loss EELS analysis of O K edge reveals a pre-edge similar to many p-type doped copper oxide superconductors, while a free charge carrier plasmon has been identified with low loss EELS. It is discovered that the delocalized hole carrier concentration in a lower-T(c) sample (argon annealed), as inferred from oscillator strengths, is about approximately 60% of that of a fully oxygenated sample, which has a higher T(c). It is also discovered that there is a strong excitation just above the delocalized hole state (by approximately 2 eV) in both lower- and higher-T(c) samples. These observations are compared with other cuprate superconductors.