Tunable Synthesis of SiC/SiO₂ Heterojunctions via Temperature Modulation

Synthesis of SiC/SiO2 core-shell nanowires with good optical properties on Ni/SiO2/Si substrate via ferrocene pyrolysis at low temperature

In this study, the high-density SiC/SiO₂ core-shell nanowires were synthesized on the nickel coated SiO₂ (100 nm)/Si substrate by chemical vapor deposition (CVD) method with ferrocene precursor at temperature 1000 °C compared to previous studies (1300-1600 °C). The present work provides an efficient strategy for the production of SiC/SiO₂ nanowires with uniform morphology and good optical properties, where the Ni layer plays important roles for this fabrication at low temperature which reduces the decomposition temperature of hydrocarbon gases and improves the growth quality of SiC nanowires. The as-synthesized SiC/SiO₂ nanowires consist of single crystal 3C structures as well as 3C structures with defects along [111] direction. In the photoluminescence (PL) spectrum, the SiC/SiO₂ core-shell nanowires revealed an obvious blueshift. The blueshift is due to the formation of nanoscale silicon carbide polytypism caused by the stacking faults in 3C-SiC and the nanoscale polytypism also caused the transition from indirect to direct bandgap which explains why the stacking faults percentage in SiC confirmed from X-ray diffraction (XRD) is 19%, but ultimately makes the strongest emission intensity. Finally, the PL characteristics are further improved by changing the diameter of the SiC nanowire and etching and an approximate model followed by the vapor-liquid-solid (VLS) mechanism was proposed to explain the possible growth mechanism of the SiC/SiO₂ nanowires.