Electronic structure and dielectric function of oxide superconductors via transmission EELS with a cold field emission TEM

Abstract

Transmission high-energy electron energy loss spectrometry (EELS) with a cold field emission transmission electron microscope (TEM) is employed to analyze the evolution of electronic structure and dialectric function of oxide superconductors. The O-K core loss spectra of p-type doped oxide superconductors are analyzed in terms of formation of holes on oxygen sites while momentum-controlled EELS is utilized to identify their crystallographic confinement in YBa 2Cu 4O 8 (Y124). The semiconductor-to-metal transition in Ba 1- x K x BiO 3 (BKBO) is monitored via low-loss EELS. Emergence of free carrier plasmons for x > 0.35 is confirmed using momentum-resolved low-loss EELS. It is argued that transmission EELS with a cold field emission TEM very much complements soft X-ray absorption and optical spectroscopy, with added advantages of high spatial resolution and its compatibility with other analytical and high-resolution TEM techniques readily available in a TEM.