Two-dimensional bismuth-rich nanosheets through the evaporative thinning of Se-doped Bi2Te3

Eve D. Hanson; Fengyuan Shi; Thomas C. Chasapis; Mercouri G. Kanatzidis; Vinayak P. Dravid

doi:10.1016/j.jcrysgro.2015.11.033

Two-dimensional bismuth-rich nanosheets through the evaporative thinning of Se-doped Bi₂Te₃

Eve D. Hanson, Fengyuan Shi, Thomas C. Chasapis, Mercouri G. Kanatzidis, Vinayak P. Dravid^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

High bulk conductance obscures the behavior of surface states in the prototypical topological insulators Bi₂Te₃ and Bi₂Se₃. However, ternary phases of Bi₂Te_3-ySe_y with balanced donor and acceptor levels may lead to large bulk resistivity, allowing for the observation of the surface states. Additionally, the contribution of the bulk conductance may be further suppressed by nanostructuring, increasing the surface-to-volume ratio. Herein we report the synthesis of a ternary tetradymite newly confined to two dimensions. Ultra-thin large-area stable nanosheets were fabricated via evaporative thinning of a Bi₂Te_2.9Se_0.1 original phase. Owing to vapor pressure differences, a compositional shift to a final Bi-rich phase is observed. The Se/Te ratio of the nanosheet increases tenfold, due to the higher stability of the Bi-Se bonds. Hexagonal crystal symmetry is maintained despite dramatic changes in thickness and stoichiometry. Given that small variations in stoichiometry of this ternary system can incur large changes in carrier concentration and switch majority carrier type, the large compositional shifts found in this case imply that compositional analysis of similar CVD and PVD grown materials is critical to correctly interpret topological insulator performance. Further, the characterization techniques deployed, including STEM-EDS and ToF-SIMS, serve as a case study in determining such compositional shifts in two-dimensional form.

Original language	English (US)
Pages (from-to)	138-144
Number of pages	7
Journal	Journal of Crystal Growth
Volume	436
DOIs	https://doi.org/10.1016/j.jcrysgro.2015.11.033
State	Published - Feb 15 2016

Funding

This material is partially based upon work supported by the Air Force Office of Scientific Research under Award no. FA9550-12-1–0280 as well as work supported by the National Science Foundation under Grant no. DMR-1507810. This work was also supported by the Department of Energy, Office of Science Basic Energy Sciences grant DE-SC0014520 . This work made use of the EPIC facility and Keck facility of the NU ANCE Center at Northwestern University, which has received support from the MRSEC Program (NSF DMR-1121262 ) at the Materials Research Center; the International Institute for Nanotechnology (IIN) ; and the State of Illinois, through the IIN.

Keywords

A1. Solid solutions
A3. Evaporative thinning
A3. Physical vapor deposition processes
B1. Nanomaterials
B2. Semiconducting ternary compounds
B2. Topological insulators

ASJC Scopus subject areas

Condensed Matter Physics
Inorganic Chemistry
Materials Chemistry

Access to Document

10.1016/j.jcrysgro.2015.11.033

Cite this

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title = "Two-dimensional bismuth-rich nanosheets through the evaporative thinning of Se-doped Bi2Te3",

abstract = "High bulk conductance obscures the behavior of surface states in the prototypical topological insulators Bi2Te3 and Bi2Se3. However, ternary phases of Bi2Te3-ySey with balanced donor and acceptor levels may lead to large bulk resistivity, allowing for the observation of the surface states. Additionally, the contribution of the bulk conductance may be further suppressed by nanostructuring, increasing the surface-to-volume ratio. Herein we report the synthesis of a ternary tetradymite newly confined to two dimensions. Ultra-thin large-area stable nanosheets were fabricated via evaporative thinning of a Bi2Te2.9Se0.1 original phase. Owing to vapor pressure differences, a compositional shift to a final Bi-rich phase is observed. The Se/Te ratio of the nanosheet increases tenfold, due to the higher stability of the Bi-Se bonds. Hexagonal crystal symmetry is maintained despite dramatic changes in thickness and stoichiometry. Given that small variations in stoichiometry of this ternary system can incur large changes in carrier concentration and switch majority carrier type, the large compositional shifts found in this case imply that compositional analysis of similar CVD and PVD grown materials is critical to correctly interpret topological insulator performance. Further, the characterization techniques deployed, including STEM-EDS and ToF-SIMS, serve as a case study in determining such compositional shifts in two-dimensional form.",

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author = "Hanson, {Eve D.} and Fengyuan Shi and Chasapis, {Thomas C.} and Kanatzidis, {Mercouri G.} and Dravid, {Vinayak P.}",

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AU - Hanson, Eve D.

AU - Shi, Fengyuan

AU - Chasapis, Thomas C.

AU - Kanatzidis, Mercouri G.

AU - Dravid, Vinayak P.

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AB - High bulk conductance obscures the behavior of surface states in the prototypical topological insulators Bi2Te3 and Bi2Se3. However, ternary phases of Bi2Te3-ySey with balanced donor and acceptor levels may lead to large bulk resistivity, allowing for the observation of the surface states. Additionally, the contribution of the bulk conductance may be further suppressed by nanostructuring, increasing the surface-to-volume ratio. Herein we report the synthesis of a ternary tetradymite newly confined to two dimensions. Ultra-thin large-area stable nanosheets were fabricated via evaporative thinning of a Bi2Te2.9Se0.1 original phase. Owing to vapor pressure differences, a compositional shift to a final Bi-rich phase is observed. The Se/Te ratio of the nanosheet increases tenfold, due to the higher stability of the Bi-Se bonds. Hexagonal crystal symmetry is maintained despite dramatic changes in thickness and stoichiometry. Given that small variations in stoichiometry of this ternary system can incur large changes in carrier concentration and switch majority carrier type, the large compositional shifts found in this case imply that compositional analysis of similar CVD and PVD grown materials is critical to correctly interpret topological insulator performance. Further, the characterization techniques deployed, including STEM-EDS and ToF-SIMS, serve as a case study in determining such compositional shifts in two-dimensional form.

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