Hari S. Solanki

Probing thermal expansion of graphene and modal dispersion at low-temperature using graphene nanoelectromechanical systems resonators.

We use suspended graphene electromechanical resonators to study the variation of resonant frequency as a function of temperature. Measuring the change in frequency resulting from a change in tension, from 300 to 30 K, allows us to extract information about the thermal expansion of monolayer graphene as a function of temperature, which is critical for strain engineering applications. We find that thermal expansion of graphene is negative for all temperatures between 300 and 30 K. We also study the dispersion, the variation of resonant frequency with DC gate voltage, of the electromechanical modes and find considerable tunability of resonant frequency, desirable for applications like mass sensing and RF signal processing at room temperature. With a lowering of temperature, we find that the positively dispersing electromechanical modes evolve into negatively dispersing ones. We quantitatively explain this crossover and discuss optimal electromechanical properties that are desirable for temperature-compensated sensors.

Magnetotransport properties of individual InAs nanowires

We probe the magnetotransport properties of individual InAs nanowires in a field effect transistor geometry. In the low magnetic field regime we observe magnetoresistance that is well described by the weak localization (WL) description in diffusive conductors. The weak localization correction is modified to weak anti-localization (WAL) as the gate voltage is increased. We show that the gate voltage can be used to tune the phase coherence length (

Tuning mechanical modes and influence of charge screening in nanowire resonators

l_\phi

Tunable thermal conductivity in defect engineered nanowires at low temperatures

) and spin-orbit length (

Facile fabrication of lateral nanowire wrap-gate devices with improved performance

l_{so}

Coupling between quantum Hall state and electromechanics in suspended graphene resonator

) by a factor of

Electromechanical resonators as probes of the charge density wave transition at the nanoscale in NbSe2

\sim

Probing thermal expansion of graphene and modal dispersion at low-temperature using graphene NEMS resonators

2. In the high field and low temperature regime we observe the mobility of devices can be modified significantly as a function of magnetic field. We argue that the role of skipping orbits and the nature of surface scattering is essential in understanding high field magnetotransport in nanowires.

High Q electromechanics with InAs nanowire quantum dots

We probe electromechanical properties of InAs nanowire (diameter

Compact, inexpensive coaxial terminations and wiring for low temperature RF applications

\ensuremath{\sim}100\text{ }\text{nm}