Improving Quality of Graphene Grown on the Copper Foil by Physical Polishing Electropolishing and Thermal Annealing Pretreatment Processes by Low Pressure Chemical Vapor Deposition

Abstract

Objective: This study aimed to investigate the influence of chemical treatments and thermal annealing on the quality of graphene films grown on copper foils using low-pressure chemical vapor deposition (LPCVD) with cyclohexane as the precursor and N2 as the carrier gas.   Method: Cu foils were subjected to physical and electropolishing with varying phosphoric acid concentrations (30-60%) and etching times (60, 90, 120 seconds), followed by thermal annealing at temperatures from 860-940 °C for 6 minutes and consistent graphene growth at 920 °C for 10 minutes. The study employed Raman spectroscopy and microscopy analyses to assess the impact of pretreatment processes, annealing temperature, and cyclohexane flow rates on graphene film quality.   Results and Discussion: Optimal conditions were identified at a 45% phosphoric acid concentration with a 90-second etching time, paired with an annealing temperature of 900 °C. This setup produced a high I2D/IG intensity ratio of 2.79, resulting in the formation of predominantly monolayer graphene films, while varying conditions led to multilayer graphene. Experimental observations also revealed that adjusting growth time and cyclohexane flow rates further enhanced the formation of monolayer graphene film.   Research Implications: The study demonstrated the critical role of precise chemical treatments and controlled thermal management in enhancing the quality of graphene films on treated copper foils. These findings provide valuable insights for optimizing growth conditions and underscore the importance of tailored processes in graphene synthesis for potential applications in various fields.