Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Jun 28;3(6):e1700685.
doi: 10.1126/sciadv.1700685. eCollection 2017 Jun.

Nanotwinned metal MEMS films with unprecedented strength and stability

Gi-Dong Sim  1 , Jessica A Krogstad  2 , K Madhav Reddy  1 , Kelvin Y Xie  1 , Gianna M Valentino  1 , Timothy P Weihs  3 , Kevin J Hemker  1   3
Affiliations

Nanotwinned metal MEMS films with unprecedented strength and stability

Gi-Dong Sim et al. Sci Adv. .

Abstract

Silicon-based microelectromechanical systems (MEMS) sensors have become ubiquitous in consumer-based products, but realization of an interconnected network of MEMS devices that allows components to be remotely monitored and controlled, a concept often described as the "Internet of Things," will require a suite of MEMS materials and properties that are not currently available. We report on the synthesis of metallic nickel-molybdenum-tungsten films with direct current sputter deposition, which results in fully dense crystallographically textured films that are filled with nanotwins. These films exhibit linear elastic mechanical behavior and tensile strengths exceeding 3 GPa, which is unprecedented for materials that are compatible with wafer-level device fabrication processes. The ultrahigh strength is attributed to a combination of solid solution strengthening and the presence of dense nanotwins. These films also have excellent thermal and mechanical stability, high density, and electrical properties that are attractive for next-generation metal MEMS applications.

Keywords: Ni alloy; metal MEMS; nanotwins; thermal and mechanical stability; ultra high strength.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1. Plane-view TEM images of the as-deposited film.
(A) Bright-field plane-view TEM image. (B) TEM-based orientation map collected using precession-assisted crystal orientation mapping.
Fig. 2
Fig. 2. Cross-sectional microstructure of the as-deposited film.
(A) Cross-sectional channeling contrast image showing the columnar microstructure of the deposited film. (B) Bright-field cross-sectional TEM micrograph. (C) Corresponding selected-area electron diffraction pattern indexed for matrix and twin orientations. (D) High-resolution TEM (HRTEM) image taken along the [011] zone axis and revealing high-density planar defects. (E) HRTEM image showing stacking faults and nanotwin lamellae on {111} planes. (F) Magnified view focusing on a few planar defects with better clarity (red, matrix; yellow, stacking fault; blue, twin).
Fig. 3
Fig. 3. Tensile stress-strain curves of three Ni-Mo-W thin films from the current study compared with previously reported nanocrystalline Ni (11), nanocrystalline Ni-W alloy (12), nanotwinned Cu (13), and polysilicon thin films (14).
The linear elastic response and ultrahigh strength are highly desirable for MEMS applications.
Fig. 4
Fig. 4. Excellent thermal and mechanical stability of the Ni83.6Mo14W2.4 films.
(A) Cumulative area fraction of the in-plane grain size of the Ni83.6Mo14W2.4 films annealed at various temperatures. (B) Cross-sectional TEM image of the film annealed for 1 hour at 600°C. FIB channeling contrast (C) and cross-sectional TEM image of a film that was loaded up to 3.1 GPa (D). No obvious changes in the columnar microstructure or twin size/spacing were observed.
See this image and copyright information in PMC

References

    1. S. E. Lyshevski, MEMS and NEMS: Systems, Devices, and Structures (CRC Press, 2002).
    1. C. T. Leondes, MEMS/NEMS Handbook Techniques and Applications (Springer, 2006).
    1. Krogstad J. A., Keimel C., Hemker K. J., Emerging materials for microelectromechanical systems at elevated temperatures. J. Mater. Res. 29, 1597–1608 (2014).
    1. Neudeck P. G., Okojie R. S., Chen L.-Y., High-temperature electronics—A role for wide bandgap semiconductors? Proc. IEEE 90, 1065–1076 (2002).
    1. Liew L. A., Zhang W. G., An L. N., Shah S., Luo R. L., Liu Y. P., Cross T., Dunn M. L., Bright V., Daily J. W., Raj R., Anseth K., Ceramic MEMS—New materials, innovative processing and future applications. Am. Ceram. Soc. Bull. 80, 25–30 (2001).

Publication types