Laser-induced organic agglomerates on 2D MoS₂ during thermal treatment

In this study, we investigate the real-time evolution of photoluminescence (PL) in MoS2 samples modified with L63MS molecules during controlled thermal treatment, unveiling a unique laser-induced molecular agglomeration process. By integrating a heater into our microscopy setup, we monitored in situ changes and discovered that between 120 °C and 180 °C, focused laser irradiation induces the formation of molecular agglomerates with heights ranging from 5 to 20 nm (as confirmed by atomic force microscopy (AFM)). Notably, after subsequent heating to 320 °C, while non-agglomerated molecules desorb, these agglomerates remain stable. Raman spectroscopy reveals that the MoS2 lattice beneath the agglomerates experiences minimal phonon mode shifts—demonstrating a protective effect—and PL measurements show a redshift in the exciton A peak due to localized strain and charge transfer effects. In contrast to previous studies on the real-time PL evolution of MoS2, our work uniquely demonstrates that controlled agglomerate formation via laser exposure not only modulates optical properties but also provides a pathway for localized functionalization of MoS2, opening new avenues for optoelectronic device engineering.