Publication Date:
2016-05-18
Description:
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 2 Se 3 films 6–10 quintuple layer (QL) thick with amorphous high-κ oxides of Al 2 O 3 and Y 2 O 3 . Large gating effect of tuning the Fermi level E 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 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 2 D /ΔV g varies with TI film thickness as ∼t −0.75 . To enhance the gating effect, a Y 2 O 3 layer thickness 4 nm was inserted into Al 2 O 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 2 Se 3 to form Bi 2 Te x Se 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 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 F for dissipationless spintronics based on well-established semiconductor technology.
Print ISSN:
0003-6951
Electronic ISSN:
1077-3118
Topics:
Physics
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