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Carbon nitride films have been synthesized by argon ion-beam sputtering from a biomolecular compound target, 8-aza-6-aminopurine (C[sub 4]N[sub 6]H[sub 4]). The compound has a six-membered ring structure similar to that existing in the hypothetical β-C[sub 3]N[sub 4]. Except for the target material, no other source of nitrogen was used during sputtering deposition. It was found that crystalline carbon nitride with high N/C atomic composition ratios of 0.43–0.56 can be formed even at room temperature. The infrared spectra of the film exhibit two peaks at 1383 and 1643 cm[sup -1], corresponding to C–N and C==N stretching modes, respectively. No detectable peak at 2200 cm[sup -1] (C=N stretching mode) is observed. Both x-ray diffraction and transmission electron microscopy show a very strong broad peak at 3.2 Å, comparable to the d spacing of the (110) orientation in the β-C[sub 3]N[sub 4] structure. However, it is suggested that the film contains a nanocrystalline phase with a crystal structure yet to be determined. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]