Breakdown Voltage in Multi Walled Carbon- Nanotubes during Low Voltage (4 V) DC Switching

A metallic coated carbon nanotube surface, developed for use in a micro-electromechanical (MEMS) switching device, is investigated for performance, when switching 4 VDC, with current levels between 10 to 600 mA; with the objective of understanding the upper limits of the surface performance. The surface used is a Gold Coated (500 nm), forest of multi-walled carbon nanotubes (50 μm), referred to as Au/CNT. The surface has been previously investigated for endurance at low current levels of 4 μA, to characterize the cold switching performance over 4 billion switching cycles and tested in a cantilever MEMs test system with 10 mA (hot switching) over 0.5 billion cycles. This investigation studies the current loading level with a focus on the transient voltages during the opening process. The investigation is undertaken using a piezoelectric (PZT) actuator, as part of an in-situ test apparatus (ICE). Results are compared to the transient voltage on a reference carbon nanotube surface without the gold coating, under the same switching conditions. The results for the Au/CNT surface show that the voltage transients are dominated by molten metal bridge phenomena up to 300 mA above which a previously unreported switching transient is observed. The higher current levels (300 to 600 mA) are shown to puncture the gold surface after 10's of switching cycles exposing the CNT. Under this condition the exposed CNT become conductive and thermally decompose (pyrolyze).