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Title: Demonstration of large field effect in topological insulator films via a high-κ back gate

Abstract

The spintronics applications long anticipated for topological insulators (TIs) has been hampered due to the presence of high density intrinsic defects in the bulk states. In this work we demonstrate the back-gating effect on TIs by integrating Bi{sub 2}Se{sub 3} films 6–10 quintuple layer (QL) thick with amorphous high-κ oxides of Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3}. Large gating effect of tuning the Fermi level E{sub F} to very close to the band gap was observed, with an applied bias of an order of magnitude smaller than those of the SiO{sub 2} back gate, and the modulation of film resistance can reach as high as 1200%. The dependence of the gating effect on the TI film thickness was investigated, and ΔN{sub 2D}/ΔV{sub g} varies with TI film thickness as ∼t{sup −0.75}. To enhance the gating effect, a Y{sub 2}O{sub 3} layer thickness 4 nm was inserted into Al{sub 2}O{sub 3} gate stack to increase the total κ value to 13.2. A 1.4 times stronger gating effect is observed, and the increment of induced carrier numbers is in good agreement with additional charges accumulated in the higher κ oxides. Moreover, we have reduced the intrinsic carrier concentration in the TI filmmore » by doping Te to Bi{sub 2}Se{sub 3} to form Bi{sub 2}Te{sub x}Se{sub 1−x}. The observation of a mixed state of ambipolar field that both electrons and holes are present indicates that we have tuned the E{sub F} very close to the Dirac Point. These results have demonstrated that our capability of gating TIs with high-κ back gate to pave the way to spin devices of tunable E{sub F} for dissipationless spintronics based on well-established semiconductor technology.« less

Authors:
; ; ; ; ; ; ; ; ;  [1]
  1. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China)
Publication Date:
OSTI Identifier:
22591736
Resource Type:
Journal Article
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 108; Journal Issue: 20; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0003-6951
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALUMINIUM OXIDES; BISMUTH SELENIDES; DENSITY; FERMI LEVEL; FILMS; LAYERS; MIXED STATES; SEMICONDUCTOR MATERIALS; SILICON OXIDES; SPIN; THICKNESS; TITANIUM SULFIDES; YTTRIUM OXIDES

Citation Formats

Wang, C. Y., Lin, H. Y., Yang, S. R., Chen, K. H. M., Kwo, J., E-mail: mhong@phys.ntu.edu.tw, E-mail: raynien@phys.nthu.edu.tw, Lin, Y. H., Chen, K. H., Young, L. B., Cheng, C. K., Fanchiang, Y. T., Hong, M., E-mail: mhong@phys.ntu.edu.tw, E-mail: raynien@phys.nthu.edu.tw, and Tseng, S. C. Demonstration of large field effect in topological insulator films via a high-κ back gate. United States: N. p., 2016. Web. doi:10.1063/1.4950849.
Wang, C. Y., Lin, H. Y., Yang, S. R., Chen, K. H. M., Kwo, J., E-mail: mhong@phys.ntu.edu.tw, E-mail: raynien@phys.nthu.edu.tw, Lin, Y. H., Chen, K. H., Young, L. B., Cheng, C. K., Fanchiang, Y. T., Hong, M., E-mail: mhong@phys.ntu.edu.tw, E-mail: raynien@phys.nthu.edu.tw, & Tseng, S. C. Demonstration of large field effect in topological insulator films via a high-κ back gate. United States. doi:10.1063/1.4950849.
Wang, C. Y., Lin, H. Y., Yang, S. R., Chen, K. H. M., Kwo, J., E-mail: mhong@phys.ntu.edu.tw, E-mail: raynien@phys.nthu.edu.tw, Lin, Y. H., Chen, K. H., Young, L. B., Cheng, C. K., Fanchiang, Y. T., Hong, M., E-mail: mhong@phys.ntu.edu.tw, E-mail: raynien@phys.nthu.edu.tw, and Tseng, S. C. Mon . "Demonstration of large field effect in topological insulator films via a high-κ back gate". United States. doi:10.1063/1.4950849.
@article{osti_22591736,
title = {Demonstration of large field effect in topological insulator films via a high-κ back gate},
author = {Wang, C. Y. and Lin, H. Y. and Yang, S. R. and Chen, K. H. M. and Kwo, J., E-mail: mhong@phys.ntu.edu.tw, E-mail: raynien@phys.nthu.edu.tw and Lin, Y. H. and Chen, K. H. and Young, L. B. and Cheng, C. K. and Fanchiang, Y. T. and Hong, M., E-mail: mhong@phys.ntu.edu.tw, E-mail: raynien@phys.nthu.edu.tw and Tseng, S. C.},
abstractNote = {The spintronics applications long anticipated for topological insulators (TIs) has been hampered due to the presence of high density intrinsic defects in the bulk states. In this work we demonstrate the back-gating effect on TIs by integrating Bi{sub 2}Se{sub 3} films 6–10 quintuple layer (QL) thick with amorphous high-κ oxides of Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3}. Large gating effect of tuning the Fermi level E{sub F} to very close to the band gap was observed, with an applied bias of an order of magnitude smaller than those of the SiO{sub 2} back gate, and the modulation of film resistance can reach as high as 1200%. The dependence of the gating effect on the TI film thickness was investigated, and ΔN{sub 2D}/ΔV{sub g} varies with TI film thickness as ∼t{sup −0.75}. To enhance the gating effect, a Y{sub 2}O{sub 3} layer thickness 4 nm was inserted into Al{sub 2}O{sub 3} gate stack to increase the total κ value to 13.2. A 1.4 times stronger gating effect is observed, and the increment of induced carrier numbers is in good agreement with additional charges accumulated in the higher κ oxides. Moreover, we have reduced the intrinsic carrier concentration in the TI film by doping Te to Bi{sub 2}Se{sub 3} to form Bi{sub 2}Te{sub x}Se{sub 1−x}. The observation of a mixed state of ambipolar field that both electrons and holes are present indicates that we have tuned the E{sub F} very close to the Dirac Point. These results have demonstrated that our capability of gating TIs with high-κ back gate to pave the way to spin devices of tunable E{sub F} for dissipationless spintronics based on well-established semiconductor technology.},
doi = {10.1063/1.4950849},
journal = {Applied Physics Letters},
issn = {0003-6951},
number = 20,
volume = 108,
place = {United States},
year = {2016},
month = {5}
}