Distinct effects of Cr bulk doping and surface deposition on the chemical environment and electronic structure of the topological insulator Bi 2 Se 3

Journal Article · Mon Feb 20 23:00:00 EST 2017 · Applied Surface Science

DOI: https://doi.org/10.1016/j.apsusc.2017.02.160 · OSTI ID:1412746

Yilmaz, Turgut ^[1]; Hines, William ^[1]; Sun, Fu-Chang ^[1]; Pletikosić, Ivo ^[2]; Budnick, Joseph ^[1]; Valla, Tonica ^[3]; Sinkovic, Boris ^[1]

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1. Univ. of Connecticut, Storrs, CT (United States)
2. Princeton Univ., NJ (United States)
3. Brookhaven National Lab. (BNL), Upton, NY (United States)

In this report, it is shown that Cr doped into the bulk and Cr deposited on the surface of Bi2Se3 films produced by molecular beam epitaxy (MBE) have strikingly different effects on both the electronic structure and chemical environment. Angle resolved photoemission spectroscopy (ARPES) shows that Cr doped into the bulk opens a surface state energy gap which can be seen at room temperature; much higher than the measured ferromagnetic transition temperature of ≈ 10 K. On the other hand, similar ARPES measurements show that the surface states remain gapless down to 15 K for films with Cr surface deposition. In addition, core-level photoemission spectroscopy of the Bi 5d, Se 3d, and Cr 3p core levels show distinct differences in the chemical environment for the two methods of Cr introduction. Surface deposition of Cr results in the formation of shoulders on the lower binding energy side for the Bi 5d peaks and two distinct Cr 3p peaks indicative of two Cr sites. These striking differences suggests an interesting possibility that better control of doping at only near surface region may offer a path to quantum anomalous Hall states at higher temperatures than reported in the literature.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: SC0012704
• OSTI ID: 1412746
• Report Number(s): BNL--114706-2017-JA; KC0207010
• Journal Information: Applied Surface Science, Journal Name: Applied Surface Science Journal Issue: C Vol. 407; ISSN 0169-4332
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English