Observation of crystalline C₃N₄

We present strong experimental evidence suggesting that we have synthesized the β-C₃N₄ phase. This is a material predicted by theory to have bulk moduli comparable to diamond. Thin films containing small crystals were deposited on Si and Ge wafers by rf diode sputtering of a pure graphite target with pure N₂. The crystal structure of these phases was investigated using X-ray and electron-beam diffractometry as well as transmission electron microscopy. Our results indicate that the β-C₃N₄ particles with typical dimensions of ∼0.5 μm are embedded in a 1-μm-thick layer of a C-N polymer. These particles are believed to crystallize preferentially on Si (100) wafers. © 1994 The American Physical Society.