Chemical vapor deposition of graphene on liquid Sn–In binary Alloys: Substrate influence and growth behaviour

The growth of graphene via chemical vapor deposition (CVD) on liquid substrates has strong potential for producing high-quality films due to the absence of grain boundaries and the atomically flat surface of the liquid phase. In this study, graphene growth was investigated on liquid Sn, In, and Sn–In binary alloys (Sn_x–In, x = 20, 50, 80 wt%) under varied growth parameters. The influence of residence time (RT) and methane/hydrogen ratio (R) was systematically evaluated in terms of layer number, defect density, and coverage. Within the experimental window, the optimum growth was obtained at RT = 6.8 s and R = 0.1, which produced thinner films with lower defect density and enhanced crystallinity, as supported by statistical Raman analysis. Energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) confirmed alloy stability at growth temperature, showing uniform elemental distribution for Sn₂₀In₈₀ and Sn₈₀In₂₀, while Sn₅₀In₅₀ exhibited localized segregation. Despite this, Raman and XPS confirmed that Sn₅₀In₅₀ yielded graphene with the lowest defect density, highlighting its catalytic balance compared with pure metals and other alloy compositions. Growth time studies identified 5 min as the optimum duration. This study underscores the critical role of alloy composition and gas flow dynamics in tailoring graphene quality and highlights the promise of low melting point binary alloys as tunable platforms for scalable, high quality graphene growth.