Graphitization of Tincone via Molecular Layer Deposition: Investigating Sulfur’s Role and Structural Impacts

This study investigated the synthesis of sp2 carbons using molecular layer deposition (MLD) with tincone, which utilized tetrakis(dimethylamido)tin (TDMASn) as the metal precursor and 4-mercaptophenol (4MP) as the organic linker. Tincone films were deposited at 100 °C without impurities and then subjected to vacuum post-annealing in a tube furnace to induce graphitization. Compositional and structural analyses revealed significant changes as the annealing temperature increased, including the breakdown of the bonds between Sn, O, S, and C . This process led to the reduction of Sn, O, and S and the formation of sp2 carbons. At 400 °C, the film thickness was reduced by 57.5%, and the refractive index increased from 1.8 to 1.97, as confirmed by the emergence of G-band and 2D-band peaks in the Raman spectra. X-ray photoelectron spectroscopy analysis indicated that the residual Sn content decreased to 0.75% at 600 °C. Interestingly, at temperatures above 400 °C, unique behavior was observed: increased C-S bonding disrupted the graphite structure due to the thiol (-SH) groups in 4MP. This disruption led to a reduction in C-C bonding and a decrease in the G-band peak in the Raman spectra. This study provides the first detailed investigation of the role of S in the graphitization of tincone, highlighting its impact on sp2 carbon formation and emphasizing the importance of the careful selection of precursors and linkers in MLD processes.