Topological surface states of Bi₂Te₂Se are robust against surface chemical modification

Abstract

The robustness of the Dirac‐like electronic states on the surfaces of topological insulators (TIs) during materials process‐ing is a prerequisite for their eventual device application. Here, the (001) cleavage surfaces of crystals of the topological insulator Bi2Te2Se (BTS) were subjected to several surface chemical modification procedures that are common for electronic materials. Through measurement of Shubnikov–de Hass (SdH) oscillations, which are the most sensitive measure of their quality, the surface states of the treated surfaces were compared to those of pristine BTS that had been exposed to ambient conditions. In each case – surface oxidation, deposition of thin layers of Ti or Zr oxides, or chemical modification of the surface oxides – the robustness of the topological surface electronic states was demonstrated by noting only very small changes in the frequency and amplitude of the SdH oscillations. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Synthesis of Sb2Se3 and Bi2Se3 Nanoparticles in Ionic Liquids at Low Temperatures and Solid State Structure of [C4C1Im]3[BiCl6]

“…A very recent XPS study clearly revealed that Bi 2 Te 3 and Bi 2 Te 2 Se easily form the corresponding oxides upon expose to air, while Bi 2 Se 3 was significantly more stable . Comparable findings were previously reported and also observed for Bi 2 Te 3 nanoparticles, which were shown to form bismuth oxides and tellurium oxides within a day upon expose to air …”

Surface State-Dominated Photoconduction and THz Generation in Topological Bi2Te2Se Nanowires

“…Such a property has facilitated the detection of spin-polarized currents generated in this compound . As another advantage, the topological surface states of BTS have been documented to be robust against chemical surface modification including oxidation under ambient conditions . Furthermore, BTS can be grown in the form of nanowires or ribbons, which are required for high-density device integration. , This renders them into valuable test structures for the implementation of TIs into future information technology circuits.…”

Surface Oxidation of Bi2(Te,Se)3 Topological Insulators Depends on Cleavage Accuracy

“…2,11−13 Yet, if new devices based on TIs, such as for spintronics and quantum computation, 2,14 are to be realized, addressing TIs through their surface chemistry must also be understood. 15,16 Indeed, precisely controlling the surface chemistry of TIs could be a prerequisite for interfacing them with other materials: Dirac states are highly surface-sensitive. 3,5 Absent packaging, a freshly cleaved sample of the TI would be exposed to air, and there are conflicting accounts as to the effects of such exposure on members of the Bi 2 (Te,Se) 3 family of TIs.…”

“…These layers are separated by a van der Waals gap, 22 which allows in principle for facile cleavage along a basal plane leading to a terraced surface that can be visualized by atomic force microscopy (AFM). 16,18 A common method to cleave these materials is to align a sharp blade parallel to the basal (0001)…”

“…Topological insulators are characterized by their unique surface electronic states, which involve a Dirac cone with linear dispersion and massless electrons that exhibit spin-momentum locking. , It is not surprising, therefore, that most research on TIs has focused on their physics, including transport measurements, − angle-resolved photoemission spectroscopy, , scanning tunneling microscopy, , and theory. ,− Yet, if new devices based on TIs, such as for spintronics and quantum computation, , are to be realized, addressing TIs through their surface chemistry must also be understood. , Indeed, precisely controlling the surface chemistry of TIs could be a prerequisite for interfacing them with other materials: Dirac states are highly surface-sensitive. , Absent packaging, a freshly cleaved sample of the TI would be exposed to air, and there are conflicting accounts as to the effects of such exposure on members of the Bi 2 (Te,Se) 3 family of TIs. ,,− In particular, several reports based on X-ray photoelectron spectroscopy (XPS) and transport measurements claim rapid, general oxidation of Bi 2 Te 3 and Bi 2 Se 3 surfaces with concomitant degradation of their TI properties. , Others use density functional theory, scanning probe microscopy, and XPS to claim that basal planes of these same species are resistant to oxidation, with defects proposed, but not demonstrated, to be sites of oxidation. ,, Herein we provide direct XPS comparison among Bi 2 Te 3 , Bi 2 Se 3 , and Bi 2 Te 2 Se aerobic oxidation profiles that shows Bi 2 Te 2 Se to be comparable in reactivity to Bi 2 Te 3 . No Se oxidation is observed, suggesting an oxide growth method different from that suggested for Bi 2 Se 3 . , We also address disparate oxidation reactivity claims through scanning photoelectron microscopy (SPEM) analysis, which provides direct experimental evidence for rapid aerobic oxidation at the step edges of Bi 2 Te 2 Se (BTS) TIs, but not, as predicted by calculation, ,, on basal planes.…”