Structure and composition of Nb and NbC layers on graphite Academic Article uri icon

abstract

  • Niobium layers of 6 to 8 μm in thickness have been deposited on an ATJ graphite substrate by radio-frequency (rf) magnetron sputtering. After deposition, the layers were annealed under vacuum (6.67× 10− 4 Pa) at a temperature in the range of 1373–2073 K for 0.5 to 3 h. The effects of the negative substrate bias voltage on the deposited niobium layers and niobium carbide layers derived by heat treatment were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Vickers microhardness test. Depending on the negative dc bias voltage, V b, applied to graphite substrates, three distinct categories of Nb and of NbC layers were formed:(a) the Nb layers deposited on graphite substrates biased to V b< 50 V, exhibited a singularly nucleated columnar structure and these layers were converted by annealing treatment into highly porous NbC layers of low hardness,(b) …

publication date

  • July 22, 2005