Improving quality of CVD graphene grown on the copper foil by physical polishing electropolishing and thermal annealing pretreatment processes

Abstract

This study optimized the pretreatment processes (physical polishing (PP), electropolishing (EP), and thermal annealing) for high-quality graphene growth on thin copper (Cu) foils. PP using Brasso solvent was applied to smoothen the substrate surface, followed by EP with H3PO4 to reduce rolling lines and surface contamination. The EP process involved different H3PO4 concentrations (30-60%) and etching times (60-120 seconds). After thermal annealing at 860-940 ºC, graphene growth was performed using direct-liquid-injection chemical-vapor deposition with cyclohexane (C6H12) as the carbon precursor and nitrogen as the carrier gas. The optimized conditions involved PP and EP with 45% H3PO4 concentration and 90 seconds etching. At an annealing temperature of 900 ºC, monolayer graphene was successfully formed. Lower cyclohexane flow rates enhanced graphene quality, achieving monolayer films with an I2D/IG ratio of 2.76 for a 10-minute growth. By optimizing growth conditions, the graphene film properties were improved. These findings highlight the importance of annealing temperature and cyclohexane flow rates in controlling graphene film quality on Cu foils, providing valuable insights for graphene synthesis in various applications.