Contact Conductance Quantization in a MEMS Switch

When the dimensions of a metallic conductor are much smaller than the mean free path of the electrons and become comparable to the Fermi wavelength, the absence of scattering results in ballistic electron transport and the conductance becomes quantized. In this paper we present original experiments carried out in air at room temperature on MEMS switches actuated by a nanoindenter apparatus. The current and voltage curve across contact electrodes were monitored and recorded continuously while opening the switch at an extremely low speed. Instead of a linear conductance curve, the presence of quantized conductance plateaus lasting up to hundreds of μs have been observed just before the separation of the two contact members. The conductance plateaus are close to integer multiples of the conductance quantum G₀ = 2e²/h. These results are consistent with theoretical predictions for quantum ballistic transport in atomic-sized contacts and show that a quantum phenomenon can easily be observed in a basic MEMS switch under ambient conditions. The influence of the nature of the contact material and current as well as the deviation between the experimental results and exact values are reviewed and discussed.