Evidence for the Eu 4f Character of Conduction-Band Edge at the Eu2O3 Surface Studied by Scanning Tunneling Spectroscopy

Abstract

<p>Effects of localized Eu 4f levels on the band gap properties of Eu₂O₃ have attracted significant fundamental and technological interest, and the band structure of such thin films has been thoroughly studied by photoelectron spectroscopies (T. Hadamek et al., J. Appl. Phys. 127 (2020) 074101). Here we apply a scanning tunneling spectroscopy (STS) to clarify the character of the conduction band (CB) bottom at the surface of epitaxial Eu₂O₃ grown on GaN(0001)/Si(111) substrates. It is shown that the CB edge is formed solely by an unoccupied Eu 4f state 0.8 eV above the Fermi level at the Eu₂O₃ surface and does not overlap with unoccupied Eu 5d6s states laying more than 2 eV higher than the bottom of the 4f band<br></p>