Abstract-Nonvolatile Solid-State Charged-Polymer Gating of Topological Insulators into the Topological Insulating Regime

R. M. Ireland, Liang Wu, M. Salehi, S. Oh, N. P. Armitage, and H. E. Katz

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.9.044003

We demonstrate the ability to reduce the carrier concentration of thin films of the topological insulator (TI) ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ by utilizing a nonvolatile electrostatic gating via corona charging of electret polymers. Sufficient electric field can be imparted to a polymer-TI bilayer to result in significant electron density depletion, even without the continuous connection of a gate electrode or the chemical modification of the TI. We show that the Fermi level of ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ is shifted toward the Dirac point with this method. Using terahertz spectroscopy, we find that the surface chemical potential is lowered into the bulk band gap (approximately 50 meV above the Dirac point and 170 meV below the conduction-band minimum), and it is stabilized in the intrinsic regime while enhancing electron mobility. The mobility of surface state electrons is enhanced to a value as high as approximately $1600{\mathrm{cm}}^2/Vs$ at 5 K.

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