A comparison of mechanical properties of three MEMS materials - Silicon carbide, ultrananocrystalline diamond, and hydrogen-free tetrahedral amorphous carbon (Ta-C)

Horacio Dante Espinosa*, B. Peng, N. Moldovan, T. A. Friedmann, X. Xiao, D. C. Mancini, O. Auciello, J. Carlisle, C. A. Zorman

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Scopus citations

Abstract

Many MEMS devices are based on polysilicon because of the current availability of surface micromachining technology. However, polysilicon is not the best choice for devices where extensive sliding and/or thermal fields are applied due to its chemical, mechanical and tribological properties. In this work, we investigated the mechanical properties of three new materials for MEMS/NEMS devices: silicon carbide (SiC) from Case Western Reserve University (CWRU), ultrananocrystalline diamond (UNCD) from Argonne National Laboratory (ANL), and hydrogen-free tetrahedral amorphous carbon (ta-C) from Sandia National Laboratories (SNL). Young's modulus, characteristic strength, fracture toughness, and theoretical strength were measured for these three materials using only one testing methodology - the Membrane Deflection Experiment (MDE) developed at Northwestern University. The measured values of Young's modulus were 430GPa, 960GPa, and 800GPa for SiC, UNCD, and ta-C, repectively. Fracture toughness measurments resulted in values of 3.2, 4.5, and 6.2 MPa×m 1/2, respectively. The strengths were found to follow a Weibull distribution but their scaling was found to be controlled by different specimen size parameters. Therefore, a cross comparison of the strengths is not fully meaningful. We instead propose to compare their theoretical strengths as determined by employing Novozhilov fracture criterion. The estimated theoretical strength for SiC is 10.6GPa at a characteristic length of 58nm, for UNCD is 18.6GPa at a characteristic length of 37nm, and for ta-C is 25.4GPa at a characteristic length of 38nm. The techniques used to obtained these results as well as microscopic fractographic analyses are summarized in the article. We also highlight the importance of characterizing mechanical properties of MEMS materials by means of only one simple and accurate experimental technique.

Original languageEnglish (US)
Title of host publication11th International Conference on Fracture 2005, ICF11
Pages3806-3811
Number of pages6
StatePublished - Dec 1 2005
Event11th International Conference on Fracture 2005, ICF11 - Turin, Italy
Duration: Mar 20 2005Mar 25 2005

Publication series

Name11th International Conference on Fracture 2005, ICF11
Volume5

Other

Other11th International Conference on Fracture 2005, ICF11
CountryItaly
CityTurin
Period3/20/053/25/05

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology

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