To obtain quantitative information about the composition and bonding of atoms located at and beyond the analyzed solid surface nondestructively, we applied angle-resolved X-ray photoelectron spectroscopy aided by the maximum entropy method to air-exposed amorphous carbon nitride films deposited by pulsed laser deposition of diamond-like carbon modified by low-energy nitrogen ion bombardment during film growth. We demonstrate that the composition, chemical bonding, and mass density vary significantly from the top surface to a shallow subsurface region. The analyzed samples, in a shallow surface region of ∼1 nm, are composed of oxygen, nitrogen, hydrogen, and mostly carbon in sp2 hybridization. In a deeper region, the C sp3 content increases substantially going to a maximum, whereas the nitrogen percentage decreases to a minimum, then increases, and tends to saturate. Special attention has been paid to in-depth distributions of carbon atoms in trigonal and tetragonal arrangements because they specify numerous physical and chemical properties of carbon-based materials. These results indicate that the interaction of DLC:N surfaces with surroundings can be influenced, barring oxygen and nitrogen, by sp2-bonded carbon atoms located near the surface of the samples. The obtained results can be useful for developing a deeper understanding of the interaction between DLC:N layer surfaces and their surroundings and particularly with living tissue.

Czech Technical University Prague Faculty of Biomedical Engineering nam Sitna 3105 27201 Kladno Czech Republic

Institute of Physics of the Czech Academy of Sciences Na Slovance 2 182 21 Prague 8 Czech Republic

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