A new critical growth parameter and mechanistic model for SiC nanowire synthesis via Si substrate carbonization: the role of H$_2$/CH$_4$ gas flow ratio

TL;DR

This study identifies key growth parameters, especially the H$_2$/CH$_4$ ratio and temperature, that control the formation of SiC nanowires versus films on Si substrates, and proposes a mechanistic model for this process.

Contribution

It introduces a new critical growth parameter and mechanistic model that explain how to selectively synthesize SiC nanowires or films based on gas flow ratios and temperature.

Findings

SiC nanowires grow when H$_2$/CH$_4$ exceeds a threshold.

The growth window for nanowires is between 1200°C and 1310°C.

A mechanistic model explains the role of gas-phase reactions and surface processes.

Abstract

SiC structures, including nanowires and films, can be effectively grown on Si substrates through carbonization. However, growth parameters other than temperature, which influence the preferential formation of SiC nanowires or films, have not yet been identified. In this work, we investigate SiC synthesis via Si carbonization using methane (CH$_4$) by varying the growth temperature and the hydrogen to methane gas flow ratio (H$_2$/CH$_4$). We demonstrate that adjusting these parameters allows for the preferential growth of SiC nanowires or films. Specifically, SiC nanowires are preferentially grown when the H$_2$/CH$_4$ ratio exceeds a specific threshold, which varies with the growth temperature, ranging between 1200$^\circ$C and 1310$^\circ$C. Establishing this precise growth window for SiC nanowires in terms of the H$_2$/CH$_4$ ratio and growth temperature provides new insights into the parameter-driven morphology of SiC. Furthermore, we propose a mechanistic model to explain the preferential growth of either SiC nanowires or films, based on the kinetics of gas-phase reactions and surface processes. These findings not only advance our understanding of SiC growth mechanisms but also pave the way for optimized fabrication strategies for SiC-based nanostructures.