Effects of phase transitions in devices actuated by the electromagnetic vacuum force

Abstract

Abstract. -We study the influence of the electromagnetic vacuum force on the behaviour of a model device based on materials, like germanium tellurides, that undergo fast and reversible metalinsulator transitions on passing from the crystalline to the amorphous phase. The calculations are performed at finite temperature and fully accounting for the behaviour of the material dielectric functions. The results show that the transition can be exploited to extend the distance and energy ranges under which the device can be operated without undergoing stiction phenomena. We discuss the approximation involved in adopting the Casimir expression in simulating nanoand micro-devices at finite temperature.Introduction. -With the development of modern technology towards smaller structures an increasing attention has been addressed to the role of electromagnetic vacuum fluctuation forces (dispersion or van der Waals and Casimir forces) in micro-and nano-electromechanical systems [1][2][3][4][5][6][7]. These forces vary typically with the third or fourth inverse power of the distance between the surfaces of the interacting bodies and therefore can be very intense in the sub-micrometer regime. When the moving parts of a device come to such a close distance, dispersion forces affect the dynamics and the operation of the device and, under certain circumstances, they can cause adhesion or stiction between the surfaces, thus limiting the device lifetime. Devices actuated by Casimir force have been designed and demonstrated [8][9][10]. Since these forces depend upon the reflectivity, the size and the geometry of the interacting parts [11,12], several possibilities can be explored to devise structures that exploit such dependence in order to improve the performance of existing devices or to design new types of devices [13]. In this paper we investigate the possibility of using materials, that undergo fast and reversible phase transitions, to extend the travel range of a device. Thermally induced phase changes between the amorphous and the polycrystalline state in a thin film have been observed since a

Fluid-sensitive nanoscale switching with quantum levitation controlled by α -Sn/ β -Sn phase transition

“…Several studies have investigated how this may be achieved through optical excitations and temperature dependent phase change materials. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] For example, crystallization of amorphous Ag-In-Sb-Te film has been predicted to increase the Lifshitz force up to 20% between gold and the alloy surface. 28 However, a phase-transition controlled sign reversal of the Lifshitz forces is a novel idea that has not to our knowledge been proposed yet.…”