Elementary excitations, such as in-plane anisotropic phonons and phonon polaritons (PhPs), in α-MoO₃ play key roles in its outstanding physical properties like high carrier mobility and ultralow phonon thermal conductivity ( ${\kappa }_{\mathrm{P}}$). Understanding the excitation mechanisms like phonon–phonon interactions is the most fundamental step to further applications. Here, we report on the systematic Raman investigations on phonon anisotropy and anharmonicity of representative Mo–O stretching vibration phonon modes (SVPMs) in physical vapor deposition (PVD)-grown α-MoO₃ flakes. Polarizations of SVPMs verify the phonon anisotropy. The abnormal temperature dependence of SVPMs reveals that giant quartic-phonon decay dominates the phonon anharmonicity in α-MoO₃. An ultrashort phonon lifetime of ~ 0.34 ps gives evidence of theoretically predicted ultralow ${\kappa }_{\mathrm{P}}$ in α-MoO₃. Our findings give deep insight into the phonon–phonon interactions in α-MoO₃ and provide an indicator for its extreme thermal device applications.

With the packing density growing continuously in integrated electronic devices, sufficient heat dissipation becomes a serious challenge. Recently, dielectric materials with high thermal conductivity have brought insight into effective dissipation of waste heat in electronic devices to prevent them from overheating and guarantee the performance stability. Layered CrOCl, an anti-ferromagnetic insulator with low-symmetry crystal structure and atomic level flatness, might be a promising solution to the thermal challenge. Herein, we have systematically studied the thermal transport of suspended few-layer CrOCl flakes by micro-Raman thermometry. The CrOCl flakes exhibit high thermal conductivities along zigzag direction, from ~ 392 ± 33 to ~ 1,017 ± 46 W·m⁻¹·K⁻¹ with flake thickness from 2 to 50 nm. Besides, pronounced thickness-dependent thermal conductivity ratio ( ${\kappa }_{\mathrm{Z}\mathrm{Z}}$/ ${\kappa }_{\mathrm{A}\mathrm{R}}$ from ~ 2.8 ± 0.24 to ~ 4.3 ± 0.25) has been observed in the CrOCl flakes, attributed to the discrepancy of phonon dispersion and phonon surface scattering. As a demonstration to the heat sink application of layered CrOCl, we then investigate the energy dissipation in graphene devices on CrOCl, SiO₂ and hexagonal boron nitride (h-BN) substrates, respectively. The graphene device temperature rise on CrOCl is only 15.4% of that on SiO₂ and 30% on h-BN upon the same electric power density, indicating the efficient heat dissipation of graphene device on CrOCl. Our study provides new insights into two-dimentional (2D) dielectric material with high thermal conductivity and strong anisotropy for the application of thermal management in electronic devices.

Doping can improve the band alignment at the metal-semiconductor interface to modify the corresponding Schottky barrier, which is crucial for the realization of high-performance logic components. Here, we systematically investigated a convenient and effective method, ultraviolet ozone treatment, for p-type doping of MoTe₂ field-effect transistors to enormously enhance the corresponding electrical performance. The resulted hole concentration and mobility are near 100 times enhanced to be ~ 1.0 × 10¹³ cm^-2 and 101.4 cm²/(V·s), respectively, and the conductivity is improved by 5 orders of magnitude. These values are comparable to the highest ones ever obtained via annealing doping or non-lithographic fabrication methods at room temperature. Compared with the pristine one, the photoresponsivity (522 mA/W) is enhanced approximately 100 times. Such excellent performances can be attributed to the sharply reduced Schottky barrier because of the surface charge transfer from MoTe₂ to MoO_x (x < 3), as proved by photoemission spectroscopy. Additionally, the p-doped devices exhibit excellent stability in ambient air. Our findings show significant potential in future nanoelectronic and optoelectronic applications.