In this study, high-temperature oxidation of single-crystal diamond and diamond films prepared by hot. lament chemical vapor deposition (HF-CVD), were characterized using thermal analysis and high-temperature in-situ Raman analysis. The measurements were performed in various temperatures up to 1300 degrees C in air and N-2 atmospheres. The results indicate that the initial oxidization temperature of diamond film deposited at 700 degrees C (D700 film) is approximate to 629 degrees C, lower than those of diamond film deposited at 900 degrees C (D900 film, approximate to 650 degrees C) and single-crystalline diamond (approximate to 674 degrees C) in air. Oxidation rate of D700 film at high temperatures appeared to be the highest among the samples studied. A likely cause lies in the fact that, compared to their D900 sample, D700 diamond film contains a larger amount of non-diamond carbon and grain boundaries. However, D900 and D700 diamond films as well as single-crystalline diamond showed no detectable weight loss and oxidization when they were heated up to 1300 degrees C in N-2 atmosphere. (c) 2009 Elsevier B.V. All rights reserved.