Near-Edge Fine Structure Analysis of Copper in Cu-Bi2Se3 Topological Insulators

Doped Topological Insulators have raised interest in the physics community because of the possible coupling/co-existence of the surface states with magnetic order induced by doping. For example, it has been observed that Cu doped Bi2Se3 is superconducting [1] below 10K. But, with more than one possible site, it is imperative to know where the dopant atom is present. So far [2] the valence state of Cu is used to determine this, and the common consensus is on Cu +1 . In this work, we use energy loss near-edge fine structure analysis (ELNES) [3] to observe the valence, local co-ordination and electronic structure around the dopant atom (Cu) in Cu-Bi2Se3. We use a Jeol 2010F to record the EEL spectra and the FEFF8.4 code [4] for ELNES simulations. The ARM200F and Nion UltraSTEM 100 MC were used to collect the HAADF-STEM images and Dr. Kirkland’s STEMSLICE code to simulate the same. Commercial samples of Cu(I)Se [Cu2Se] and Cu(II)Se [CuSe] were used as references.