Effect of the ZrCl_4 static vaporiser system and deposition time on growth characteristics of chemical vapour deposited zirconium carbide layers

摘要

ZrC layers were deposited from ZrCl4-Ar-CH4-H-2 gas mixture in a home-built vertical wall chemical vapour deposition system within the deposition time range 0.5-2.5h. The flow behaviour of ZrCl4 from the static vaporiser system to reaction chamber as a function of time was studied. To investigate the microstructure evolution and the growth characteristics of ZrC layers with deposition time, the growth rate, microstructure, morphology and composition were analysed. The layer thickness increased with deposition time all through; however, its growth rate increased up to 1.0h and thereafter declined. The X-ray diffraction (XRD) analysis showed both ZrC and carbon peaks. The intensity of the carbon peaks followed a non-linear trend with deposition time. The average crystallite size and the number of crystallites per unit volume of the layers increased with deposition time. The orientation of crystallographic plane also varied with the deposition time. At short deposition times, the Raman spectra showed the acoustic and optic branches indicating that the ZrC deposited contained carbon vacancies. The D and G peaks of carbon increased as the deposition time increased, an indication of free carbon in the deposited layers. At short deposition times, the surface morphology of the layers was relatively flat and smooth. The particle size and agglomerations also increased with time.