  In this work, we use charge extraction via organic overlayer deposition to
lower the chemical potential of topological insulator Bi2Se3 thin films into
the intrinsic (bulk-insulating) regime. We demonstrate the tuning and
stabilization of intrinsic topological insulators at high mobility with
low-cost organic films. With the protection of the organic charge extraction
layers tetrafluorotetracyanoquinodimethane(F4TCNQ) or
tris(acetylacetonato)cobalt(III) (Co(acac)3), the sample is stable in the
atmosphere with chemical potential ~135 meV above the Dirac point (85 meV below
the conduction band minimum, well within the topological insulator regime)
after four months, which is an extraordinary level of environmental stability.
The Co complex represents the first use of an organometallic for modulating TI
charge density. The mobility of surface state electrons is enhanced as high as
~2000 cm2/Vs. Even at room temperature, a true topologically insulating state
is realized and stabilized for months' exposure to the atmosphere.
