Corrugated, concaved vertically aligned carbon nanotube structures in impeded CVD growth conditions

Abstract

Vertically Aligned Carbon Nanotubes (VACNT) are promising soft materials in advanced devices, including wearable strain sensors. VACNT uniform growth depends on nucleation, growth, and deactivation of metal seed catalysts by chemical vapor deposition (CVD) at specific process conditions. CVD is performed at controlled process conditions to maximize VACNT growth with iron seed catalysts of various sizes, optimize water vapor concentration for enhanced VACNT growth, and probe their morphology by creating competition of the hydrocarbon feedstock to Fe seed catalyst of selected layer thicknesses. The analytical studies include ellipsometry to measure thermal oxide, barrier layer, and catalyst layer thicknesses; Raman spectroscopy to assess the characteristic peaks of carbon nanotubes; as well as scanning electron microscopy to evaluate VACNT morphology. The findings show a maximum VACNT growth of 1284 µm at 1 nm Fe catalyst, optimum water vapor content at 12.5–20 SCCM, and predominantly concaved and corrugated, a tube chamber position-dependent VACNT structures with low Ar/H2 ratio and C2H4 gas rates.