Optical characterization of exfoliated MoSe2 and WSe2 thin films deposited by Langmuir-Blodgett assembly

This work demonstrates the Langmuir–Blodgett (LB) assembly of liquid-phase exfoliated MoSe 2 and WSe 2 flakes into optically active thin films on SiO 2 substrates and correlates their structural, morphological, and optical responses. XRD, SEM, and TEM confirms the polycrystalline 2H phase of both transition metal dichalcogenides, with interplanar spacings consistent with the reported values. Atomic force microscopy reveals apparent thicknesses of ∼1.2 nm for MoSe 2 and ∼5 nm for WSe 2 , indicating laterally non-uniform films composed of few-layer regions and multilayer aggregates. Raman spectra show the characteristic (in-plane) and (out-of-plane) vibrational modes with layer-dependent peak separation. UV–Vis absorption spectra exhibit bandgap energy approximately at 1.62 eV and 1.6 eV for MoSe 2 and WSe 2 , respectively. Photoluminescence is dominated by emission from localized thinner regions within the LB films, underscoring the strong influence of thickness distribution and film morphology on excitonic behavior. These results highlight LB assembly as a scalable route to deposit non-uniform but optically active MoSe 2 and WSe 2 films. • Langmuir–Blodgett assembly of MoSe 2 and WSe 2 thin films demonstrated. • Structural and morphological properties confirmed by XRD, SEM, TEM, AFM. • Non-uniform films with few-layer and multilayer nanosheet regions observed. • Optical bandgaps ∼1.62 eV (MoSe 2 ) and ∼1.6 eV (WSe 2 ) extracted. • Photoluminescence dominated by excitonic emission from thinner regions.