Time-dependent structural and surface evolution of g-C3N4 thin films developed by direct current magnetron sputtering

Graphitic carbon nitride (g-C3N4) thin films were synthesized using an indigenously developed direct current magnetron sputtering system to systematically investigate the influence of deposition time on their structural, chemical, and surface properties. The films deposited for 30, 35, and 40 min were analyzed using x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy (AFM). XPS analysis revealed that 35 min deposition condition yields a highly polymerized and structurally ordered g-C3N4 framework dominated by C=N—C bonding with minimal defect-related components. In contrast, shorter deposition resulted in incomplete polymerization and higher defect density, leading to structurally inferior films, while prolonged deposition caused structural degradation and nitrogen depletion. Raman spectra further confirmed enhanced polymerization and preserved heptazine/triazine features at 35 min, with longer deposition showing loss of characteristic modes. AFM analysis indicated that the 35 min film possessed the highest surface roughness, particle size, and fractal complexity, indicating increased surface complexity and active sites. These features are critical for improving surface-mediated processes such as photocatalysis. Overall, the study establishes 35 min as the optimal sputtering duration for achieving structurally robust and surface-optimized g-C3N4 thin film, highlighting their strong potential for applications in photocatalysis and optoelectronic devices.