THE THERMAL-STABILITY OF DIAMOND-LIKE CARBON

Diamond-like carbon (DLC) is a potential, low-cost substitute for diamond in certain applications, but little is known of the temperature range over which its desirable properties are retained. We have investigated the stability of DLC films at elevated temperature and high humidity using Raman spectroscopy, Auger electron spectroscopy and thermal desorption analysis. Exposure to boiling water and a hot (225 degrees C), humid environment does not appear to affect the DLC structure. Thermal desorption analysis detected the onset of hydrogen evolution from DLC in vacuum at 260 degrees C. Raman spectra show the conversion from DLC to nano-crystalline graphite (''glassy'' carbon) beginning at 300 degrees C in ambient air. Auger spectroscopy confirms the conversion of sp(3)-bonded carbon to sp(2)-bonded carbon above 300 degrees C Conversion to nano-crystalline graphite is complete by 450-600 degrees C in air. The structure and properties of DLC films are expected to be retained up to temperatures of at least 260 degrees C.