Growth of Boron Carbide Nanostructures on Silicon Using Hot Filament Chemical Vapour Deposition

Abstract

Boron carbide nanostructures were grown on Si wafers through introduction of a mixture of B2O3 dissolved in methanol using hot filament chemical vapour deposition. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), Raman spectroscopy and the four-point probe technique were applied to characterise the properties of the boron carbide nanostructures. The XRD results showed that two kinds of boron carbide chemical compounds (B4C and B2C2) were deposited and the effect of boron concentration was significant. The FESEM images showed that the boron carbide nanostructures are made of crystal clusters with a cauliflower-like shape, in which the grain boundaries appear more clearly with increasing boron concentration. In addition, the AFM results showed that the surface roughness of the boron carbide films decreased with increasing boron concentration due to grain boundary diffusivity. The Raman spectrum results confirmed the presence of a B4C network and G and D bands. The results of the four-point probe method indicated that samples with higher boron incorporation showed the lowest sheet resistance (0.06 ω sq−1), which may be because of the decrease in inter-grain boundaries caused by the larger cluster size. This study suggests that higher boron incorporation in boron carbide nanostructures results in larger crystal clusters, higher thickness and lower film resistivity.