Carbon nitride thin films have been prepared by reactive ionized cluster beam (RICB) technique, using low molecular weight polyethylene as evaporation material and NH 3 , N 2 as reactive gas. Rutherford backscattering measurements show that the composition ratio, N/C, as high as 0.67, can be obtained. Transmission electron microscopy investigations suggest that the films contain the crystalline β-C 3 N 4 phase. Infrared absorption measurements indicate that chemical bonds are formed between carbon and nitrogen atoms. The results also show that the structure of the films varied mainly with the RICB parameters: ionization current and acceleration voltage.