Nano Archive

Tailoring the microstructure and surface morphology of metal thin films for nano-electro-mechanical systems applications

Luber, E. and Mohammadi, R. and Ophus, C. and Lee, Z. and Nelson-Fitzpatrick, N. and Westra, K. and Evoy, S. and Dahmen, U. and Radmilovic, V. and Mitlin, D. (2008) Tailoring the microstructure and surface morphology of metal thin films for nano-electro-mechanical systems applications. NANOTECHNOLOGY, 19 (12).

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Metallic structural components for micro-electro-mechanical/nano-electro-mechanical systems (MEMS/NEMS) are promising alternatives to silicon-based materials since they are electrically conductive, optically reflective and ductile. Polycrystalline mono-metallic films typically exhibit low strength and hardness, high surface roughness, and significant residual stress, making them unusable for NEMS. In this study we demonstrate how to overcome these limitations by co-sputtering Ni-Mo. Detailed investigation of the Ni-Mo system using transmission electron microscopy and high-resolution transmission electron microscopy (TEM/HRTEM), x-ray diffraction (XRD), nanoindentation, and atomic force microscopy (AFM) reveals the presence of an amorphous-nanocrystalline microstructure which exhibits enhanced hardness, metallic conductivity, and sub-nanometer root mean square (RMS) roughness. Uncurled NEMS cantilevers with MHz resonant frequencies and quality factors ranging from 200-900 are fabricated from amorphous Ni-Mo. Using a sub-regular solution model it is shown that the electrical conductivity of Ni-Mo is in excellent agreement with Bhatia's structural model of electrical resistivity in binary alloys. Using a Langevin-type stochastic rate equation the structural evolution of amorphous Ni-Mo is modeled; it is shown that the growth instability due to the competing processes of surface diffusion and self-shadowing is heavily damped out due to the high thermal energies of sputtering, resulting in extremely smooth films.

Item Type:Article
Subjects:Physical Science > Nanophysics
Material Science > Nanofabrication processes and tools
Engineering > Nanotechnology applications in mechanical engineering
Technology > Manufacturing processes for nanotechnology
Physical Science > Nanoelectronics
Engineering > Nanotechnology applications in ICT
ID Code:6316
Deposited By:IoN
Deposited On:16 Dec 2009 16:38
Last Modified:16 Dec 2009 16:38

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