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

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 ～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 sp² and sp³ hybridized carbon atoms.