Silicon-on-insulator cantilevers as charge collectors for radioisotope micropower sources: design, fabrication and characterization

Abstract

A silicon-on-insulator cantilever is proposed as a potential charge collector for radioisotope micropower sources. The conversion efficiency can be improved by directional control of the radiated particles. A two-dimensional microfluidic modeling was successfully generated to analyze the performance of the radiated particles as a quick proof of concept using ANSYS™. The mounting of the radiation source and the release of charged particles in this novel approach are simple and practical from the point of view of fabrication and operation. Prototype cantilevers were fabricated at the millimeter scale to increase the amount of collected charge and obtain a higher fabrication yield. A processing technique, using a thin copper foil as a gap protector, was successfully created to resolve the stiction issues for freestanding silicon-on-insulator cantilevers with their length and width at the millimeter scale and their thickness at tens of micrometers. The vibration of these prototypes was characterized through a self-made feedback interferometer. The difference between the measured natural frequency and the finite-element analysis is less than 0.4%, an extremely high accuracy pertaining to the nanofabrication tolerances in device dimensions. The proposed self-made feedback interferometer presents an efficient solution to calibrate the vibration of microdevices with their dimensions at the millimeter scale. The analytical deflection of the silicon-on-insulator cantilevers with charged particles was rigorously derived, which shows only a 1.5% difference from the three-dimensional electromechanical coupled-field simulation using ANSYS™, an excellent accuracy and an extremely simple solution.