Mechanical Properties of Undoped and Doped Ultrananocrystalline Diamond. Elasticity, Strength, and Toughness.

This chapter investigates the elasticity, toughness, and strength of Ultrananocrystalline Diamond (UNCD) and the validity of the Weibull statistical analysis. The fracture strength of UNCD thin films is obtained by testing submicron free-standing films by means of the membrane deflection experiment. The Weibull modulus, m, and the scale parameter, σ₀, are obtained by analyzing the tensile data. The applicability of the Weibull statistics in prediction of the strength of doped and undoped UNCD thin films is examined. A particular emphasis is placed on assessing the role of volume vs. surface in the prediction of the material strength. The chapter begins with a description of the investigated materials and a short description of the testing methodologies, followed by the reporting of experimental results including fractographic observations. A statistical analysis of the reported data based on maximum likelihood estimation is used to identify Weibull parameters. The discussion of results and their implication in the design of micro-electromechanical systems MEMS/NEMS based on UNCD are also discussed in the chapter.