Mechanical measurements of ultra-thin amorphous carbon membranes using scanning atomic force microscopy

Abstract

The elastic modulus of ultra-thin amorphous carbon films was investigated by integrating atomic force microscopy (AFM) imaging in contact mode with finite element analysis (FEA). Carbon films with thicknesses of ∼10nm and less were deposited on mica by electron beam evaporation and transferred onto perforated substrates for mechanical characterization. The deformation of these ultra-thin membranes was measured by recording topography images at different normal loads using contact mode AFM. The obtained force-distance relationship at the center of membranes was analyzed to evaluate both the Young’s modulus and pre-stress by FEA. From these measurements, Young’s moduli of 178.9±32.3, 193.4±20.0, and 211.1±44.9GPa were obtained for 3.7±0.08, 6.8±0.12, and 10.4±0.17nm thick membranes, respectively. Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were used for characterizing the chemical and structural properties of the films, including the content of sp2 and sp3 hybridized carbon atoms.