Detectors of SPM cantilever deflection based on field emission phenomenon

The most common deflection detection methods for micro-electromechanical systems (MEMS), like microcantilevers used in scanning probe microscopy, include optical methods based on optical beam deflection systems, piezoresistive or capacitive methods. This issue is still being pursued in order to develop a method with the highest possible deflection sensitivity. For this reason, attention is focused on exploiting the field emission phenomenon – the tunnelling of electrons through a potential barrier that occurs when the applied threshold voltage between electrodes is exceeded.
This work presents a method for microcantilever deflection detection based on field emission phenomenon – fig. 1a. As a result of cantilever deflection, the distance between the emitter tips (electrodes) was changed, resulting in a variation of the threshold voltage and field emission current. Nanotip field emitters were integrated into the microcantilevers using a focused electron and ion beam induced deposition (FEBID/FIBID) (fig. 1b). This one-step process allowed for the simplification of their fabrication technology. The effect of distance between electrodes and emitter shape on the emission enhancement factor was analysed. Preliminary usability tests of the sensor have been performed.
Acknowledgements: This work was supported by the National Science Centre, Poland PRELUDIUM-21 grant [“Nanometrology of field emission phenomena from electron beam deposited nanowires operating as nano- and picodeflection sensors – FEmet”, grant number 2022/45/N/ST7/03049]; and a short term scientific mission funded by the COST Action CA19140 (http://www.fit4nano.eu/).