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Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films

DOI: 10.1038/srep22935 DOI Help

Authors: A. Figueroa (Diamond Light Source) , G. Van Der Laan (Diamond Light Source) , S. E. Harrison (Stanford University; University of Oxford) , G. Cibin (Diamond Light Source) , T. Hesjedal (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Scientific Reports , VOL 6

State: Published (Approved)
Published: March 2016
Diamond Proposal Number(s): 11119

Open Access Open Access

Abstract: The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi3+ in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the lowdoping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state.

Journal Keywords: EXAFS, XAFS, Magnetism

Subject Areas: Physics, Materials, Engineering

Diamond Offline Facilities: no
Instruments: B18-Core EXAFS

Other Facilities: No