Ultrathin nitrogenated carbon (CNx) films were synthesized using pulsed dc magnetron sputtering. The influence of substrate tilt angle and rotation speed on surface roughness was explored. Atomic force microscopy studies showed that the smoothest films were obtained at substrate tilt of 45degrees and rotation speed 20-25 rpm, corresponding to 2-3 rotations per deposited atomic layer. The root-mean-square surface roughness under these optimum conditions is similar to0.3 nm when sampled over 20 X 20 mum(2) areas, increasing to similar to0.4 nm when sampled over similar to0.05 X 3 cm(2) using x-ray reflectivity measurements. In addition, x-ray reflectivity measurements showed that the mass density of these CNx films is similar to2.0 gm/cc, independent of film thickness from similar to1 to 10 nm, consistent with ion beam analysis. (C) 2003 American Vacuum Society.