Experimental Realization of the Covalent Solid Carbon Nitride
Chunming Niu 1,
Yuan Z. Lu 2, and
Charles M. Lieber 3
1 Department of Chemistry, Harvard University, Cambridge, MA 02138
2 Materials Research Laboratory, Harvard University, Cambridge, MA 02138
3 Department of Chemistry and Division of Applied Sciences, Harvard University, Cambridge, MA 02138
Pulsed laser ablation of graphite targets combined with an intense, atomic nitrogen source has been used to prepare C-N thin film materials. The average nitrogen content in the films was systematically varied by controlling atomic nitrogen flux. Rutherford backscattering measurements show that up to 40 percent nitrogen can be incorporated on average into these solids under the present reaction conditions. Photoelectron spectroscopy further indicates that carbon and nitrogen form an unpolarized covalent bond in these C-N materials. Qualitative tests indicate that the C-N solids are thermally robust and hard. In addition, strong electron diffraction is observed from crystallites within the films. Notably, analysis of these diffraction data show that the only viable structure for the C-N crystallites is that of 
-C3N4, a material predicted theoretically to exhibit superhardness. The experimental synthesis of this new C-N material offers exciting prospects for both basic research and engineering applications.
Submitted on May 10, 1993
Accepted on June 4, 1993
