Atomic force microscopy and photoemission electron microscopy study of the low-pressure oxidation of transition metal nitrides

The oxidation of transition metal nitrides is examined by atomic force microscopy (AFM) and photoemission electron microscopy (PEEM) in the temperature range of 25-800 degrees C in an ultrahigh vacuum study. The roughness of the surfaces of thin film coatings of vanadium (V), vanadium nitride (VN), titanium nitride (TiN), and TiAlVN, monitored as a function of (a) constant dose of 50 000 L (1 L=10(-6) Torr s) O-2 at various temperatures and (b) oxygen dose at a constant temperature of 800 degrees C, is found to increase for all samples except TiAlVN. The morphological parameters (roughness and oxide grain volume) obtained from AFM are used to determine the extent of oxidation. The activation energy for the growth of oxide on the surface is calculated to be in the range of 0.4-0.5 eV for all samples containing V atoms and 1.6 eV for TiN. PEEM images of the pristine surfaces of TiN and TiAlVN show surface precipitates of the order of 5-50 mu m size. The workfunction of all surfaces and precipitates, obtained from photoemission spectra using PEEM, in combination with the effective activation energies measured by AFM, suggests that the main surface precipitate of TiAlVN is VN or VOxNy. (C) 2007 American Institute of Physics.