Enhanced surface mobility and quantum oscillations in topological insulator Bi1.5Sb0.5Te1.7Se1.3 nanoflakes

Abstract

In this study, a series of Bi1.5Sb0.5Te1.7Se1.3 (BSTS) flakes 80-nm to 140-μm in thickness was fabricated to investigate their metallic surface states. We report the observation of surface-dominated transport in these topological insulator BSTS nanoflakes. The achievement of surface-dominated transport can be attributed to high surface mobility (∼3000 cm2/V s) and low bulk mobility (12 cm2/V s). Up to 90% of the total conductance, the surface channel was estimated based on the thickness dependence of electrical conductance and the result of the Shubnikov-de Hass oscillations in a 200-nm BSTS. The nature of nontrivial Dirac surface states was also confirmed by the weak anti-localization effect.

Thickness-dependent conductance in Sb2SeTe2 topological insulator nanosheets

“…This is different from the reported result that the sheet conductance is independent of the thickness in 2D TMDs 29 . These results support that other sources contribute to the measured conductivity in addition to the layer transport carriers 21 . We propose that these characteristics originate from the peculiar band structure of the topological insulator, and the observed thickness-dependent sheet conductance originates from the combination of the surface state and the bulk state.…”

“…The extracted G s  = 8.7 (e 2 /h) and σ b  = 2.76 × 10 −2 (e 2 /h) nm −1 . σ b is larger than the reported value in the Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 topological insulator nanoflake by a factor of 5 21 .

Figure 2The inset shows the conductivity as a function of thickness in a log-log plot. The conductance decreases as the thickness increases.

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Low carrier concentration crystals of the topological insulator Bi2−xSbxTe3−ySey: a magnetotransport study

“…In table 2 we have collected the fit parameters ϕ l and α, as well as those obtained for BSTS nanoflakes reported in the recent literature. Hsiung et al [37] measured a flake with enhanced surface mobility and reported an α-value close to −1 as well. The α-values reported by Xia et al [32] obtained on a relatively thick nanoflake are systematically smaller than −1.…”

Quantum oscillations of the topological surface states in low carrier concentration crystals of Bi2−xSbxTe3Pan1, Никитин2, Wu3 et al. 2016Solid State Communications7100View full textAdd to dashboardCite

“…Therefore, the SdH effect in TIs has received ample attention in the literature, notably through experiments carried out on bulk crystals of Bi 2 Te 3 , Bi 2 Se 3 and Bi 2 Te 2 Se [12,11,26,27,28]. In addition, the SdH effect was reported for nonstochiometric BSTS (x, y)=(0.50,1.3) bulk crystals [29] and nanoflakes [30]. In most cases, the phase offset of the quantum oscillations obtained from a linear Landau level plot has been interpreted as a finite Berry phase.…”