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.