Fracture toughness of tetrahedral amorphous diamond-like carbon specimens of various thicknesses

Krishna Jonnalagadda, Sung Woo Cho, Ioannis Chasiotis

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

Abstract

We present fracture toughness measurements conducted on Hydrogen-free tetrahedral amorphous Diamond-like Carbon (ta-C) MEMS-scale specimens with thickness in the range of 0.5 - 3μm. Edge pre-cracks were generated in uniform gage specimens via microindentation of the supporting SiO 2 sacrificial layer. One of the indentation cracks propagated in the SiO 2 layer and into the ta-C specimen generating a mathematically sharp crack. The precise crack length was determined using an Atomic Force Microscope (AFM). The pre-cracked specimens were released from the sacrificial SiO 2 via wet etch and mode-I micro-tensile tests were performed on the freestanding specimens. Since ta-C is perfectly brittle the mode-I fracture toughness K IC was computed using the linear elastic fracture mechanics solution (LEFM). K IC was found to be 4.25 ± 0.7 MPa√m for 0.5 μm specimens, 4.4 ± 0.4 MPa√m for 1 μm specimens, and 3.06 ± 0.17 MPa√m for 3 μm specimens. Unlike macroscale specimens, this thickness dependence of fracture toughness is not attributed to a plane stress state. Rather, the observed trends may have arisen from through-the-thickness compositional variations and residual stresses.

Original languageEnglish (US)
Title of host publicationProceedings of the 2005 SEM Annual Conference and Exposition on Experimental and Applied Mechanics
Pages1109-1114
Number of pages6
StatePublished - 2005
Event2005 SEM Annual Conference and Exposition on Experimental and Applied Mechanics - Portland, OR, United States
Duration: Jun 7 2005Jun 9 2005

Publication series

NameProceedings of the 2005 SEM Annual Conference and Exposition on Experimental and Applied Mechanics

Other

Other2005 SEM Annual Conference and Exposition on Experimental and Applied Mechanics
Country/TerritoryUnited States
CityPortland, OR
Period6/7/056/9/05

Keywords

  • Fracture toughness
  • MEMS
  • Mechanical properties
  • Ta-C
  • Thin films

ASJC Scopus subject areas

  • Engineering(all)

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