Reducing sensor dimension is a good way to increase system sensitivity and response. However the advantages gained must be weighed against other effects which also became significant during the scaling process. In this paper, the scaling effect of cantilever sensors from micrometre to nanometre regimes is reviewed. Changes in the physical properties such as Q-factor, Young's modulus, noise and nonlinear deflections, as well as effects on practical sensor applications such as sensor response and sensor readouts, are presented. Since cantilever is an elemental transducer and device building block, its scaling effects can be further extrapolated to other sensing systems and applications.

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Hybrid superconducting circuits, which integrate nonsuperconducting elements into a circuit quantum electrodynamics (cQED) architecture, expand the possible applications of cQED. Building hybrid circuits that work in large magnetic fields presents even further possibilities, such as the probing of spin-polarized Andreev bound states and the investigation of topological superconductivity. Here we present a magnetic-field compatible hybrid fluxonium with an electrostatically tuned semiconducting nanowire as its nonlinear element. We operate the fluxonium in magnetic fields up to 1 T and use it to observe the f0-Josephson effect. This combination of gate tunability and field compatibility opens avenues for the control of spin-polarized phenomena using superconducting circuits and enables the use of the fluxonium as a readout device for topological qubits.

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Isolation from the environment determines the extent to which charge is confined on an island, which manifests as Coulomb oscillations, such as charge dispersion. We investigate the charge dispersion of a nanowire transmon hosting a quantum dot in the junction. We observe rapid suppression of the charge dispersion with increasing junction transparency, consistent with the predicted scaling law, which incorporates two branches of the Josephson potential. We find improved qubit coherence times at the point of highest suppression, suggesting novel approaches for building charge-insensitive qubits. @en

Response of nanomechanical resonant mass sensors to adsorption does not only depend on the mass loading, but also on the adsorbate stiffness, adsorption induced surface stresses and location. It is therefore clear that with just resonance frequency measurement, decoupling the stiffness and the mass effects is difficult. A recent theory proposed using the electrostatic pull-in instability (EPI), in combination with the resonance frequency to decouple the aforementioned opposing effects, is presented hereof. In this paper, by performing experiments of adsorption on cantilevers, we 1) performed preliminary experiments on EPI stiffness measurement and show the stiffness effects of typical mass deposition, 2) show that EPI can be used in combination with the frequency measurements, to quantitatively analyze both the stiffness and the mass of the adsorbed material.@en

Micro/nano resonant cantilevers with a laser deflection readout have been very popular in sensing applications over the past years. Despite the popularity, however, most of the research has been devoted to increasing the sensitivity, and very little attention has been focused on effects-induced errors. Among these effects, the surface effects and the so-called readout back-action are the two most influential causes of errors. In this paper, we investigate (1) the influence of the surface effects such as water adsorption, gas adsorption, and generally surface contaminations, and (2) the effect of the laser deflection detection, including power and positions of the laser, on the resonance frequency of silicon cantilevers. Our results show that both the surface contaminations and the laser back-action effects can significantly change the resonant response of the cantilevers. We conclude that the effects have to be taken into account, particularly in the case of ultra high sensitivity cantilevers.@en

The size-dependent elastic behavior of silicon nanocantilevers and nanowires, specifically the effective Young's modulus, has been determined by experimental measurements and theoretical investigations. The size dependence becomes more significant as the devices scale down from micro- to nano-dimensions, which has mainly been attributed to surface effects. However, discrepancies between experimental measurements and computational investigations show that there could be other influences besides surface effects. In this paper, we try to determine to what extent the surface effects, such as surface stress, surface elasticity, surface contamination and native oxide layers, influence the effective Young's modulus of silicon nanocantilevers. For this purpose, silicon cantilevers were fabricated in the top device layer of silicon on insulator (SOI) wafers, which were thinned down to 14 nm. The effective Young's modulus was extracted with the electrostatic pull-in instability method, recently developed by the authors (H Sadeghian et al 2009 Appl. Phys. Lett. 94 221903). In this work, the drop in the effective Young's modulus was measured to be significant at around 150 nm thick cantilevers. The comparison between theoretical models and experimental measurements demonstrates that, although the surface effects influence the effective Young's modulus of silicon to some extent, they alone are insufficient to explain why the effective Young's modulus decreases prematurely. It was observed that the fabrication-induced defects abruptly increased when the device layer was thinned to below 100 nm. These defects became visible as pinholes during HF-etching. It is speculated that they could be the origin of the reduced effective Young's modulus experimentally observed in ultra-thin silicon cantilevers.@en

Measuring frequency shift of a resonator to obtain information on mass and force is common in the fields of micro-electromechanical systems (MEMS). Typically on a cantilever structure, the method uses the spring-mass equation of the cantilever, together with the measured frequency shift, extracts the force parameters and makes a sensor. Although popular and widely accepted as a good method, we showed in our work that this method has a fundamental problems and may induce large errors if scaling the device into nanometer dimensions. The problem is mainly because the frequency shift method cannot decouple force change from stiffness change, therefore surface contaminations, adsorptions of the atmospheric elements can cause the cantilever to shift its resonance frequency without any external force interaction. We showed in this work the importance of the issue and experimentally measured the surface induced error; furthermore, the more sensitive the sensor, the more susceptible it may be to this fundamental issue of the frequency-shift method. We found out that by simply exposing the device to ambient environment is enough to cause a significant error in the measurement.@en

The elastic behavior of silicon nanocantilevers and nanowires, and specifically the effective Young's modulus has been shown by previous experimental measurements and theoretical investigations to be size-dependent.@en

This letter presents the application of electrostatic pull-in instability to study the size-dependent effective Young's Modulus E (~170-70 GPA) of [110] silicon nanocantilevers (thickness ~1019-40nm). The presented approach shows substantial advantages over the previous methods used for characterization of nanoelectromechanical systems behaviors. The E is retrieved from the pull-in voltage of the structure via the electromechanical coupled equation, with a typical error of@en

Previous experimental and theoretical investigations have reported that the mechanical properties of silicon nanocantilevers, in particular the effective Young's Modulus, deviate from their bulk properties. This size-dependence has been attributed to surface effects. However, differences in experimental and computational investigations imply that there could be other influences besides surface effects. In this paper, we try to determine to what extent the surface effects, like surface stress, surface elasticity, surface contaminatiion and native oxide layers influence the effective Young's Modulus of silicon nanocantilevers. Si films are thinned down to 14 nm on silicon on insulator (SOI) wafers. Si cantilevers are fabricated and the effective Young's Modulus is measured with the pull-in method, recently developed by the authors. The comparison between theoretical models and experimental measurements demonstrates that, although the surface effects influence the effective Young's Modulus of silicon to some extent, they alone are insufficient to explain why the effective Young's Modulus decreases somewhat earlier. For Si films thinner than 50 nm, it is observed that the density of fabricated induced defects abruptly rises when the SOI device layer becomes thinner. A potential explanation is found in the appearance of pinholes. These pinholes, which were created during the thinning process and are made visible with HF etching, could influence the experimentally obtained effective Young's Modulus of ultra-thin Si cantilevers. Keywords: nanocantilever, size-dependence, silicon on insulator, surface stress, pull-in voltage, pinholes.@en

In this paper the temperature effect on [110] Silicon cantilevers is analyzed and measured in the range of 25 - 100°C. The quasi-static electrostatic pull-in instability method developed recently for ultra-thin cantilevers ["Characterizing Size-dependent Effective Elastic Modulus of Silicon Nanocantilevers Using Electrostatic Pull-in Instability", Applied Physics Letters, Vol. 94 (22), p. 221903, 2009] is employed to measure the temperature sensitivity of ultra-thin cantilevers. A temperature sensitivity of 81.3°C/V is obtained. the temperature sensitivity is mostly due to the temperature dependence of the effective Young's Modulus of silicon. It is shown that changes in geometrical dimensions due to the change in temperature can be neglected. The changes in the effective Young's Modulus due to the changes in temperture are extracted using an electromechanical-coupled system. The pull-in method showed substantial advantages over other methods used for the study of the thermal effects on micron and sub-micron structures. The results demonstrate a new concept for a temperature sensor with ultra high sensitivity. Keywords: temperature sensitivity, pull-in instability, cantilever, nanoelectromechanical systems.@en

Laser beam deflection is a well-known method commonly used in detecting resonance frequencies in atomic force microscopes and in mass/force sensing. The method focuses a laser spot on the surface of cantilevers to be measured, which might change the mechanical properties of the cantilevers and affect the measurement accuracy. In this work we showed that the joule heating of the laser, besides other extrinsic effects such as surface contamination, can cause a significant amount of shift in the resonator. The longer and softer the cantilever is, the more significant the effect. We suggest that the laser effects on the resonant response of sensors have to be taken into account.@en