A study of the dewetting behavior of platinum-thin-films on silicon was carried out to determine how variation of dewetting parameters affects the evolution of film morphology and to pinpoint which parameters yielded the smallest, most circular features. Platinum film thickness as well as dewetting time and temperature were varied and the film morphology characterized by means of scanning electron microscopy (SEM) analysis. Two different pathways of dewetting predicted in the literature (Vrij 1966 Discuss. Faraday Soc. 42 23, Becker et al 2003 Nat. Mater. 2 59-63) were observed. Depending on the initial criteria, restructuring of the film occurred via hole or droplet formation. With increased annealing time, a transition from an intermediate network structure to separated islands occurred. In addition, the formation of multilayered films, silicide crystals and nanowires occurred for certain parameters. Nevertheless, the dewetting behavior witnessed could be related to physical processes. Droplets with a mean diameter of 9 nm were formed by using a 1.5 nm thick platinum film annealed at 800 °C for 30 s. To demonstrate the suitability of the annealed films for further processing, we then used the dewetted films as masks for reactive ion etching to transfer the pattern into the silicon substrate, forming tapered nanopillars.

This paper introduces the use of nonlinear jump phenomena in the frequency response of a quartz crystal resonator for mass detection. In contrast to recent studies that exploit parametric excitation for mass detection, our device exhibits nonlinear behavior modeled by the directly forced Duffing equation. In addition, internal resonance due to modal coupling is demonstrated for sufficiently large forcing amplitudes. A system of coupled Duffing equations based on a Galerkin expansion of the von Kármán plate equations is used to model these higher order effects.

Nonlinear modal interactions have recently become the focus of intense research in micro- and nanoscale resonators for their use to improve oscillator performance and probe the frontiers of fundamental physics. However, our understanding of modal coupling is largely restricted to clamped-clamped beams, and lacking in systems with both geometric and material nonlinearities. Here we report multistable energy transfer between internally resonant modes of an electroelastic crystal plate and use a mixed analytical-numerical approach to provide new insight into these complex interactions. Our results reveal a rich bifurcation structure marked by nested regions of multistability. Even the simple case of two coupled modes generates a host of topologically distinct dynamics over the parameter space, ranging from the usual Duffing bistability to complex multistable behaviour and quasiperiodic motion.

No abstract

This paper presents a significantly improved quartz crystal microbalance (QCM) with sub-picogram mass sensing resolution in liquid while maintaining a high quality factor (Q) without much loss. Our design removes the liquid damping effect through an acoustic loss isolation layer (vacuum) and a sensing diaphragm, which reduce the direct contact area at the interface between the QCM and liquid. The vacuum-gapped QCM turns out to have a very high resonant Q in liquid of 196,340, only a 13.2% reduction from the Q in air. The device sensitivity is 6 cm 2 /g, corresponding to a remarkably high mass resolution of 90 fg/cm 2 in liquid.