Structural properties of hydrogenated carbon-nitride films produced by ion-beam-assisted evaporation of the molecular precursor C4N6H4

Hydrogenated carbon-nitride films (CNx:H) were deposited by evaporation of aza-adenine (8-aza-6-aminopurine, C4N6H4) and irradiated during film growth by a nitrogen ion beam with energies of 25, 50, and 100 eV. The relationship between the deposition conditions and the chemical bonding structure was investigated by x-ray photoelectron and infrared spectroscopies. The mass density of the films was estimated from the C 1s plasmon energy and the optical properties were examined by ultraviolet-visible spectroscopy. The infrared spectra indicate that in the case of evaporated films, the molecular structure of aza-adenine is preserved without substantial nitrogen loss (N/C approximate to 1.3). With increasing energy of the assisting nitrogen ion beam, the structure is subsequently transformed into an amorphous phase. This transition is accompanied by an increasing nitrogen loss down to N/C approximate to 0.8, a decrease of the optical band gap, and an increase of the film density. The known molecular structure of aza-adenine permits the reconstruction of the C 1s and N 1s core-level spectra with deconvoluted spectral components representing the different bonding environments of C and N atoms present in the molecule. The spectral components are identified by comparing the experimental data with theoretical calculations of the corresponding binding energies. By analysis of the spectral changes induced by the nitrogen ion beam with increasing energies, it is possible to study the microstructural modifications of the material. (C) 2001 American Institute of Physics.