Low-temperature synthesis of high-quality graphene by controlling the carbon-hydrogen ratio of the precursor

Abstract

A furnace-free inductively coupled plasma chemical vapor deposition (ICP-PECVD) system, which does not require sample heating, was used to grow graphene at a temperature below 300 °C. This studies have found that under low-temperature PECVD growth conditions, liquid precursors are more suitable for preparing low-temperature graphene precursors than gaseous precursors.​​​​ Hence, benzene is used as a carbon precursor to obtain a sheet resistance of approximately 1.24 kΩ sq−1. In this research, it was discovered that the carbon-hydrogen ratio of the precursor molecule is an important factor while using PECVD to grow graphene. This factor affects the quality of graphene and the sheet resistance value —when the carbon–hydrogen ratio for the precursor molecule is 1:1, graphene has the high quality and lowest sheet resistance; when it is less than 1:2, the graphene that cannot be deposited has the worst quality and sheet resistance. Furthermore, we found that methane, a precursor often used to deposit graphene, will etch graphene under low-temperature conditions, and that acetylene can be used as a precursor to deposit graphene. It was further proven that the carbon–hydrogen ratio of the precursor molecules in the PECVD process caused the reduction in the graphene temperature.