Dependence of bimaterial cantilever deflection on the coating thickness n thermal sensitivity

What is it about?

We theoretically determine the optimum coating thickness for the greatest sensitivity of the bimaterial cantilevers considering the size effects of the metallic layer. A nonmonotonic deflection versus the coating thickness is seen when the size effects on the thermal conductivity and the stiffness are taken into account. The greatest sensitivity is seen at a lower value of the coating thickness in comparison to the values obtained in a recent experiment. For silicon cantilevers of thickness less than 3 μm, the greatest sensitivity is found for a coating to cantilever thickness ratio of 0.05–0.2 corresponding to the gold coating thickness of 40–150 nm. Especially, for much thicker cantilevers, e.g., up to 20 μm, the optimum coating thickness is not greater than 180 nm. For aluminum coating, the nonmonotonic behavior is not found, i.e., there is no optimum sensitivity in the range of available coating thickness, the thicker the coating thickness, higher the sensitivity. The obtained results could give useful information for the fabrication of cantilevers with the greatest thermal sensitivity.

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Why is it important?

Thickness-dependence of thermal conductivity and mechanical rigidity in a bimaterial cantilever have been adopted. Cantilever deflection has been examined and shown a nonmonotomic dependence on the thickness.