The thermal conductivity of a particulate composite film of diamond in AlN deposited on silicon was measured using 3 omega technique in the temperature range of 205-300 K. The experimental results of increase in the temperature of heater line were analyzed using a model of film on semi-infinite substrate. The results of modeling are found to conform to the expected. temperature dependence of the thermal conductivity of silicon, AlN, and diamond. Oxygen introduced during the deposition of the AlN-diamond composite film on silicon is found to reduce the thermal conductivity of the film and the substrate. Low cost AlN-diamond particulate composite films are found to offer good heat spreader characteristics for high power semiconductor devices. (c) 2006 American Vacuum Society.