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 similar to 10 nm 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 +/- 44.9 GPa were obtained for 3.7 +/- 0.08, 6.8 +/- 0.12, and 10.4 +/- 0.17 nm 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 sp(2) and sp(3) hybridized carbon atoms.