Photoluminescence of hydrogenated amorphous carbon nitride films after ultraviolet light irradiation and thermal annealing

Abstract

The photoluminescence (PL) of hydrogenated amorphous carbon nitride films and its behaviors due to ultraviolet (UV) light irradiation and thermal annealing have been investigated. The films were produced using an electron cyclotron resonance plasma with various mixtures of N2 and CH4 gases. The broad PL spectra centered around 2.3 eV have been observed in air at room temperature and the PL intensity is inversely proportional to the concentration of nitrogen in the film. The UV irradiation results in the modification of configuration and increase of the PL intensity. Moreover, a new luminescence center around 2.76 eV occurs in the film with higher nitrogen content. The changes in film properties due to UV irradiation correlate with the incorporation of nitrogen in the film. Different from the effects of UV irradiation, thermal annealing promotes graphitization of the film. The PL intensity decreases with red shift as annealing temperature increases and is completely quenched when the temperature is over 400 °C. The changes of PL spectra are discussed on the basis of a model in which the sp2 clusters are considered as luminescence centers.