Fano resonance-induced asymmetric scissors modes and anharmonic interactions in MoO₃ nanostructures

MoO₃ nanostructures (NSs) have emerged as a potential candidate for field-effect transistors, thermoelectronic, and optoelectronic devices because of their wide range of stoichiometry, exceptional structural, optical, and electrical properties. Controlling electron-phonon (e-ph) interactions in MoO₃ NSs by structural phase tuning offers an efficient way to tailor the charge-carrier mobility, heat transport, and non-radiative transitions for these next-generation devices. The present temperature-dependent and laser power-dependent Raman studies on Fano line shapes of oxygen defect-sensitive scissors modes (c axis) revealed significant e-ph interactions in α-MoO₃, compared to h/α-MoO₃, and h-MoO₃ NSs at higher temperatures and laser power. At higher temperatures, the optical phonons in these MoO₃ NSs interact with an electronic continuum of thermally excited donor-level electrons, resulting in non-radiative intraband transitions. The temperature-dependent photoluminescence spectroscopy was employed to investigate these non-radiative intraband transitions. The density functional theory calculations revealed that α-MoO₃ exhibited a significantly higher oxygen defect stability (c axis) than h/α-MoO₃ and h-MoO₃. Therefore, the e-ph interactions in α-MoO₃ are enhanced by the substantial oxygen defects (c axis) in comparison to other phases. In addition, a method has been proposed to determine the charge density of states [N(E_F)] of 59.14 (eV)⁻¹ quantitatively in α-MoO₃ using a laser power-dependent study, which can also be applied to similar semiconducting oxides. Through structural phase control, our findings explain e-ph interactions, non-radiative transitions, and thermal transport in MoO₃ for field-effect transistors, optoelectronic, and thermal device applications.