Rigorous analysis of Casimir and van der Waals forces on a silicon nano-optomechanical device actuated by optical forces

Abstract

Nano-optomechanical devices have enabled a lot of interesting scientific and technological applications. However, due to their nanoscale dimensions, they are vulnerable to the action of Casimir and van der Waals (dispersion) forces. This work presents a rigorous analysis of the dispersion forces on a nano-optomechanical device based on a silicon waveguide and a silicon dioxide substrate, surrounded by air and driven by optical forces. The dispersion forces are calculated using a modified Lifshitz theory with experimental optical data and validated by means of a rigorous 3D FDTD simulation. The mechanical nonlinearity of the nanowaveguide is taken into account and validated using a 3D FEM simulation. The results show that it is possible to attain a no pull-in critical point due to only the optical forces; however, the dispersion forces usually impose a pull-in critical point to the device and establish a minimal initial gap between the waveguide and the substrate. Furthermore, it is shown that the geometric nonlinearity effect may be exploited in order to avoid or minimize the pull-in and, therefore, the device collapse.

Optical Trapping and Positioning of Silicon Nanowires via Photonic Nozzling

“…We assumed a small separation distance of 5 nm between the wire and the substrate. We anticipate that the downward radiation pressure on the wire will press it close to the substrate, and at a distance in the proximity of 5 nm the van der Waals forces will dominate, bringing the wire into contact with the substrate. , A previous study on the stability of silica and silicon nanoparticles, however, has shown that hydroxyl groups on the surface of the particles will create an electrostatic repulsion force and prevent the particles from sticking to the substrate or to each other. − Knowing the vertical force on the wire from preliminary simulation, we balance the thermal equipartition energy against the vertical radiation pressure force to obtain a measure of the offset distance. This calculation yields a gap distance between 3 and 5 nm, and for all simulations this gap was set to 5 nm.…”

Controlling the atom-sphere interaction with an external electric field

“…It is a multidisciplinary field that has sparked much interest for decades in different areas, such as chemistry, biology, colloid science, quantum field theory, and material science (see [2][3][4] and references therein). Due to their fluctuating nature, these ubiquitous forces typically present an attractive character, which can lead to undesirable effects in nano and micromechanical systems like adhesion and stiction [5][6][7][8][9]. It has been an important issue and gave rise to a significant search for engineering configurations that exhibit repulsive forces.…”

Electrodynamic Force, Casimir Effect, and Stiction Mitigation in Silicon Carbide Nanoelectromechanical Switches

“…A lot of theoretical and experimental research progress in EDF has been reported, including computational methods, experiments to precisely measure the EDF, and inducing repulsive forces by immersing the two plates in adequate fluid. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Furthermore, recent progress in on-chip actuation and sensing for Casimir force measurement, as well as the demonstration of non-monotonic Casimir force using complex shapes, provides important guidelines and new possibilities for reducing the EDF using shape or geometry engineering. [35,36] In contact-mode M/NEMS switches, more extensive investigations, including complete analysis of the origin of the EDF using experimentally relevant device dimensions, and methods for systematically reducing the chance of stiction using surface engineering, are necessary and imperative, to avoid stiction-induced failure and to extend the lifetime of M/NEMS switches.…”