Temperature effect on the nitrogen insertion in carbon nitride films deposited by ECR

Abstract

The impact of the temperature on the local structure of carbon nitride coating a-C 1-x N x:H was investigated by spectroscopic analysis. A set of carbon nitride films were deposited at several substrate temperatures (77 K, 300 K, 673 K and 900 K) by electron cyclotron resonance (ECR) ion gun technique fed of CH 4/N 2 plasma. The films were in situ characterized by X-ray photoelectron spectroscopy (XPS). A drastic decrease of the nitrogen content was observed when increasing the deposition temperature from 77 K to 900 K. Qualitative structural and electronic changes were followed after air exposure by infrared (FTIR), near-edge X-ray absorption fine structure (NEXAFS) and Ultraviolet photoelectron (UPS) spectroscopy. Below 300 K, the films are hydrogenated with aliphatic structure and nitrogen is bonded to carbon in many kind of configuration. Between 300 K and 600 K, the nitrogen amount is reduced while both the aromatic and the aliphatic carbons increase. The local structure of the films radically changes at 900 K, whereas the nitrogen surrounding is the same at 673 K. In that case the hydrogen fraction into the films is reduced to zero. The increase of the sp 3 carbon as well as the ratio π⁎/ σ⁎ on the nitrogen K edge can be observed. This behaviour may be explain by nitrogen substituted to sp 2 carbon which induces local changes in the distribution of the π⁎ states.