Metallic NEMS components fabricated from nanocomposite Al–Mo films

Abstract

We have fabricated fully released nano-electro-mechanical system (NEMS) cantilevers ofvarious geometries from metallic alloy nanocomposite films. At thicknesses of 4.3 and20.0 nm, these are the thinnest released metal cantilevers reported in the literatureto date. Such device dimensions are very difficult to achieve using conventionalmetal films. We were able to overcome this limitation by using room-temperatureco-sputtering to synthesize nanocomposite alloy films of Al–Mo. A systematicinvestigation of microstructure and properties as a function of Mo content resulted in anoptimum film composition of Al–32 at.%Mo with a unique microstructure comprisinga dense distribution of nano-scale Mo crystallites dispersed in an amorphousAl-rich matrix. These films were found to exhibit unusually high nanoindentationhardness and a very significant reduction in roughness compared with pure Al,while maintaining resistivity in the metallic range. A single-anchored cantilever5 µm long, 800 nm wide and 20 nm thick showed a resonance frequency of 608 kHz, yielding aYoung’s modulus of 112 GPa, in good agreement with a reduced modulus of 138 GPameasured by nanoindentation.