The copper nitride thin films were prepared on glass substrate by RF magnetron sputtering method. At pure nitrogen atmosphere, the nitrogen flow rate affects the copper nitride thin films' structures. Only a little part of nitrogen atoms insert into the body center of Cu3N structure and parts of nitrogen atoms insert into Cu3N crystallites boundary at higher nitrogen flow rate. But the indirect optical energy gap, E-opg, decreases with increasing nitrogen flow rate. The typical value of E-opg, is 1.57 eV. In a nitrogen and argon mixture atmosphere, when the nitrogen partial was less than 0.2 Pa at 50 sccm total flow rate, the (1 1 1) peak of copper nitride appears. Thermal decomposition temperature of Cu3N thin films deposited in pure nitrogen and 30 sccm flow rate was less than 300 degrees C. The surface morphology was smooth. (c) 2005 Elsevier B.V. All rights reserved.