We present a design approach that enables monolithic integration of high-quality-factor (Q) radio-frequency (RF) microelectromechanical systems (MEMS) resonators with CMOS electronics. Commercially available CMOS processes that feature two polysilicon layers and field oxide isolation can be used to implement this approach. By using a nonplanar resonator geometry in conjunction with mechanical stress in polycrystalline silicon (poly) gate layers, we create rigid and robust mechanical structures with efficient electromechanical transduction.

Interferometric imaging of normal mode dynamics in electromechanical resonators, oscillating in the rf regime, is demonstrated by synchronous imaging with a pulsed nanosecond laser. Profiles of mechanical modes in suspended thin film structures and their equilibrium profiles are measured through all-optical Fabry-Perot reflectance fits to the temporal traces. As a proof of principle, the mode patterns of a microdrum silicon resonator are visualized, and the extracted vibration modes and equilibrium profile show good agreement with numerical estimations.

Nanomechanical resonators operating in vacuum are capable of detecting and weighing single biomolecules, but their application to the life sciences has been limited by viscous forces that impede their motion in liquid environments. A promising approach to avoid this problem, encapsulating the fluid within a mechanical resonator surrounded by vacuum, has not yet been tried with resonant sensors of mass less than ∼100 ng, despite predictions that devices with smaller effective mass will have proportionally finer mass resolution.

Resonant RF MEMS structures can offer excellent performance for integrated sensing and RF signal processing applications. MEMS devices offer small size and low power consumption and improved physical parameters such as FQ product; however, significant impediments to a large scale commercial adoption include: production cost, difficulty of implementation and signal transduction.

We demonstrate that silicon-polymer composite microbridges provide a robust means of water vapor detection at ambient pressure. Volumetric changes in the reactive polymer alter the tension in a doubly clamped structure leading to large and rapid changes in the resonance frequency. We demonstrate stress-based sensing of water vapor in ambient pressure nitrogen using doubly clamped buckled beams coated with a hygroscopic polymer. We show stress sensitivity of around 20 kPa (∼170 ppb of water vapor) and subsecond response time for coated microbridges.

We probe electromechanical properties of InAs nanowire (diameter ∼100nm) resonators where the suspended nanowire is also the active channel of a field-effect transistor. We observe and explain the nonmonotonic dispersion of the resonant frequency with dc gate voltage (Vgdc). The effect of electronic screening on the properties of the resonator can be seen in the amplitude. We observe the mixing of mechanical modes with V gdc. We also experimentally probe and quantitatively explain the hysteretic nonlinear properties, as a function of Vg dc, of the resonator using the Duffing equation.

We demonstrate the use of anodic bonding to fabricate cells with characteristic size as large as 7×10mm2, with height of ≈640 nm, and without any internal support structure. The cells were fabricated from Hoya SD-2 glass and silicon wafers, each with 3 mm thickness to maintain dimensional stability under internal pressure. Bonding was carried out at 350 °C and 450 V with an electrode structure that excluded the electric field from the open region. We detail fabrication and characterization steps and also discuss the design of the fill line for access to the cavity.

Anodic bonding was used to fabricate a 10 mm diameter × 640 nm tall annular geometry suitable for torsion pendulum studies of confined 3He. For pure 3He at saturated vapor pressure the inertia of the confined fluid was seen to be only partially coupled to the pendulum at 160 mK. Below 100 mK the liquid's inertial contribution was negligible, indicating a complete decoupling of the 3He from the pendulum. © 2009 Springer Science+Business Media, LLC.

We present the preliminary results of our studies of superfluid 3He in a 0.6 μm thick slab using NMR. Below T c the A phase is observed, and at low pressures the region of stability of the A phase extends down to the lowest temperatures reached, as described elsewhere. At pressures above 3.2 bar another, so far unidentified phase is observed at low temperatures. In this article we focus on the behavior of this phase and the transition between this phase and the A phase, all studied at 5.5 bar.

We present the first study of the phase diagram of a thick film of superfluid 3He confined within a nanofabricated slab geometry. This cryogenic microfluidic chamber provides a well-defined environment for the superfluid, in which both the regular geometry and surface roughness may be fully characterised. The chamber is designed with a slab thickness d=0.6 μm and 3 mm thick walls to allow pressure tuning of the effective confinement between 0 and 5.5 bar. Over this range the zero temperature superfluid coherence length, ξ 0, decreases by approximately a factor of two from 77 to 40 nm.