Analysis of Thickness and Quality factor of a Double Paddle Oscillator at Room Temperature.

In this paper, we evaluate the quality (Q) factor and the resonance frequency of a double paddle oscillator (DPO) with different thickness using analytical, computational and experimental methods. The study is carried out for the 2nd anti-symmetric resonance mode that provides extremely high experimental Q factors on the order of 105. The results show that both the Q factor and the resonance frequency of a DPO increase with the thickness at room temperature.

Hydrogen-free amorphous silicon with no tunneling states.

The ubiquitous low-energy excitations, known as two-level tunneling systems (TLSs), are one of the universal phenomena of amorphous solids. Low temperature elastic measurements show that e-beam amorphous silicon (a-Si) contains a variable density of TLSs which diminishes as the growth temperature reaches 400 °C. Structural analyses show that these a-Si films become denser and more structurally ordered. We conclude that the enhanced surface energetics at a high growth temperature improved the amorphous structural network of e-beam a-Si and removed TLSs. This work obviates the role hydrogen was previously thought to play in removing TLSs in the hydrogenated form of a-Si and suggests it is possible to prepare "perfect" amorphous solids with "crystal-like" properties for applications.

Shear modulus of monolayer graphene prepared by chemical vapor deposition.

We report shear modulus (G) and internal friction (Q(-1)) measurements of large-area monolayer graphene films grown by chemical vapor deposition on copper foil and transferred onto high-Q silicon mechanical oscillators. The shear modulus, extracted from a resonance frequency shift at 0.4 K where the apparatus is most sensitive, averages 280 GPa. This is five times larger than those of the multilayered graphene-based films measured previously. The internal friction is unmeasurable within the sensitivity of our experiment and thus bounded above by Q(-1) ≤ 3 × 10(-5), which is orders-of-magnitude smaller than that of multilayered graphene-based films. Neither annealing nor interface modification has a measurable effect on G or Q(-1). Our results on G are consistent with recent theoretical evaluations and simulations carried out in this work, showing that the shear restoring force transitions from interlayer to intralayer interactions as the film thickness approaches one monolayer.

An ultra-high Q silicon compound cantilever resonator for Young's modulus measurements.

We describe the design of ultra-high Q mechanical cantilever resonators, fabricated from single-crystal silicon wafers. The mechanical resonance mode at f ≈ 8.5 kHz achieves a background damping of Q(-1)