Irradiation Effect of Nitrogen Ion Beam on Carbon Nitride Thin Films
- PDF / 358,499 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 49 Downloads / 191 Views
R3.2.1
Irradiation Effect of Nitrogen Ion Beam on Carbon Nitride Thin Films Shinichiro Aizawa, Yuka Nasu, Masami Aono, Nobuaki Kitazawa, and Yoshihisa Watanabe Dept. of Materials Science and Engineering, National Defense Academy, Kanagawa 239-8686, Japan ABSTRACT Irradiation effect of low-energy nitrogen ion beam on amorphous carbon nitride (a-CNx) thin films has been investigated. The a-CNx films were prepared on silicon single crystal substrates by hot carbon-filament chemical vapor deposition (HFCVD). After deposition, the CNx films were irradiated by a nitrogen ion beam with energy from 0.1 to 2.0 keV. Irradiation effect on the film microstructure and composition was studied by SEM and XPS, focusing on the effect of nitrogen ion beam energy. Surface and cross sectional observations by SEM reveal that the as-deposited films show a densely distributed columnar structure and the films change to be a sparsely distributed cone-like structure after irradiation. It is also found that 2.0 keV ions skeltonize the films more clearly than 0.1 kev ions. Depth profiles of nitrogen in the films observed by XPS show that nitrogen absorption into films is more prominent after irradiation by 0.1 keV nitrogen ions than 2.0 keV ions.
INTRODUCTION Crystalline carbon nitride (β -C3N4) has attracted much attention after the prediction by Liu and Cohen in 1989 [1], and many researchers have tried to synthesize this material using various techniques, such as laser ablation deposition [2], ion beam assisted deposition [3], reactive sputtering [4] and hot-filament chemical vapor deposition (HFCVD) [5]. The last method, HFCVD, has the advantage of being simple and utilizing less expensive equipment, but it also has the disadvantage of contamination from the filament material. The present authors have developed a carbon-filament CVD system and, as a result, contamination free amorphous carbon nitride (a-CNx) films have been successfully prepared [6]. Although the prepared films were composed of carbon and nitrogen, the atomic ratio of nitrogen to carbon in the prepared films was found to be about 0.1 and far from the theoretical value for the stoichiometric β-C3N4 , 1.33. Another technique for preparing a-CNx is nitrogen ion implantation into carbon materials [7, 8]. After irradiation by 500 eV nitrogen ions on graphite and diamond, Gousman et al [8] found that the nitrogen concentration increases and implanted nitrogen was present in three different bonding states of nitrogen and carbon. On the analogy of their expreiments, it is expected that nitrogen ion irradiation on a-CNx films is effective for increasing the nitrogen content in the films. Based on this motivation, the present authors have started to study the effect of post-deposition irradiation by nitrogen ions on a-CNx films [9]. The previous study showed that nitrogen ions were chemically combined with the a-CNx films and the atomic ratio of nitrogen to carbon was increased up to 0.3 after 300 min irradiation by 0.1 keV nitrogen ions [9]. In the previous work, the nitrogen ion
Data Loading...
