Work functions of transition metal nitride and carbide thin films were measured. The materials investigated were ZrN, NbN, HfN, TaN, HfC, and TaC. The films were prepared either by radio-frequency magnetron sputter deposition or by ion beam assisted deposition. The work function was measured by Kelvin probe in air. The work functions of ZrN and HfN ranged between 4.6 and 4.7 eV, and were similar to or slightly lower than that of NbN and TaN, 4.7 or 4.8 eV. The work function of TaC was approximately 5.0 eV. The higher work function of carbide may be attributed to lower electronegativity of carbon as compared to nitrogen. (C) 2003 American Vacuum Society.