Scanning tunneling microscopy of defect states in the semiconductorBi2Se3

Abstract

Scanning tunneling spectroscopy images of Bi 2 Se 3 doped with excess Bi reveal electronic defect states with a striking shape resembling clover leaves. With a simple tight-binding model, we show that the geometry of the defect states in Bi 2 Se 3 can be directly related to the position of the originating impurities. Only the Bi defects at the Se sites five atomic layers below the surface are experimentally observed. We show that this effect can be explained by the interplay of defect and surface electronic structure.

Atomically smooth ultrathin films of topological insulator Sb2Te3

“…The interaction between two adjacent QLs is of the van der Waals type [9]. A cleaved surface of a bulk crystal is usually Te-terminated with an unreconstructed (1 × 1)-Te structure [20][21][22]. Similar to the well-known layer-by-layer growth of GaAs with an As4 molecular beam [38], ideal MBE growth of a Sb 2 Te 3 film in units of a QL along the [111] direction should be possible with a Te 2 molecular beam under Te-rich conditions.…”

“…These gapless surface states, protected by time-reversal symmetry, are very robust. So far, topological surface states have been observed in Bi 1-x Sb x , Bi 2 Se 3 , and Bi 2 Te 3 [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26].…”

In-Plane Magnetic Anisotropy of Fe Atoms onBi2Se3(111)

“…Substrate corrected spectra (inset) prove that the resonance has a considerably stronger intensity and is shifted closer to the DP for the type B Fe atoms. Similar resonances have been observed on the Se vacancies [17,18] and were attributed to Coulomb scattering of the topological surface state by the impurity [8,18]. For a magnetic characterization, x-ray absorption spectra (XAS) at the Fe L 3,2 absorption edges (between 690 eV and 740 eV) were recorded in the surface sensitive total electron yield mode for different angles θ between the Bi 2 Se 3 surface normal and the x-ray beam direction.…”

“…This DP binding energy is typical for naturally grown Bi 2 Se 3 crystals, which are known to be electron doped due to the presence of Se vacancies observable in STM images ( Fig. 1(a)) [17,18]. Upon deposition of Fe ( Fig.…”

Solution to the Hole-Doping Problem and Tunable Quantum Hall Effect in Bi2Se3 Thin Films

“…Unlike conventional semiconductor materials, the problem is complicated due to the presence of both surface and bulk states in topological insulators: we have to consider the doping problem of the surface and the bulk states separately. Both the surface and bulk states of Bi2Se3 have a strong tendency toward n-type due to its native n-type defects such as selenium vacancies [1][2][3][11][12][13][14][15][16][17] . In bulk crystals compensation dopants such as Ca and Mn can be used to convert the dominant carrier type from n-to p-type [18][19][20][21][22][23][24][25] .…”