2 research outputs found
Few-Hundred GHz Carbon Nanotube Nanoelectromechanical Systems (NEMS)
We study 23–30 nm long suspended single-wall carbon
nanotube
quantum dots and observe both their stretching and bending vibrational
modes. We use low-temperature DC electron transport to excite and
measure the tubes’ bending mode by making use of a positive
feedback mechanism between their vibrations and the tunneling electrons.
In these nanoelectromechanical systems (NEMS), we measure fundamental
bending frequencies <i>f</i><sub>bend</sub> ≈ 75–280
GHz and extract quality factors <i>Q</i> ∼ 10<sup>6</sup>. The NEMS's frequencies can be tuned by a factor of 2 with
tension induced by mechanical breakjunctions actuated by an electrostatic
force or tension from bent suspended electrodes
Gate Controlled Photocurrent Generation Mechanisms in High-Gain In<sub>2</sub>Se<sub>3</sub> Phototransistors
Photocurrent in photodetectors incorporating
van der Waals materials is typically produced by a combination of
photocurrent generation mechanisms that occur simultaneously during
operation. Because of this, response times in these devices often
yield to slower, high gain processes, which cannot be turned off.
Here we report on photodetectors incorporating the layered material
In<sub>2</sub>Se<sub>3</sub>, which allow complete modulation of a
high gain, photogating mechanism in the ON state in favor of fast
photoconduction in the OFF state. While photoconduction is largely
gate independent, photocurrent from the photogating effect is strongly
modulated through application of a back gate voltage. By varying the
back gate, we demonstrate control over the dominant mechanism responsible
for photocurrent generation. Furthermore, because of the strong photogating
effect, these direct-band gap, multilayer phototransistors produce
ultrahigh gains of (9.8 ± 2.5) × 10<sup>4</sup> A/W and
inferred detectivities of (3.3 ± 0.8) × 10<sup>13</sup> Jones,
putting In<sub>2</sub>Se<sub>3</sub> among the most sensitive 2D materials
for photodetection studied to date