Study of the modification of the hydrophobic properties of thin carbon films via thermo-assisted Tip-Enhanced Raman Scattering method

The chemical composition and optical properties of amorphous carbon films of various thicknesses in the range from 1 to 100 nm on a series of optical fibers were characterized by using far-and near-field Raman spectroscopy. For the first time the presence of a hysteresis of the resistance of a thin carbon film was observed in ambient environment. The Raman spectrum of carbon film in the region of 1000-2000 cm−1 was fitted and well reproduced using seven individual components that were assigned to the oxygen- and hydrogen-containing functional groups defect graphene. Besides that, the thermo-assisted Tip-Enhanced Raman Scattering (TERS) method provided the evidence of the formation of a water molecule in carbon coatings. We propose that during the heat treatment the fraction of functional groups on the initial film structures changes in comparison with room temperature. Such structural modifications of carbon film can lead to a violation of hydrophobic properties of carbon coatings due to temperature change. These findings may provide opportunities for technical design of carbon-based devices.