Layer Dependence of Thermally Induced Quantum Confinement and Higher Order Phonon Scattering for Thermal Transport in CVD-Grown Triangular MoS<sub>2</sub>
Ankita Singh, Bishnu Pada Majee, Jay Deep Gupta, Ashish Kumar Mishra
Abstract
Heat dissipation and electron–phonon interaction hindering the charge carrier mobility are serious constraints for the fabrication of various integrated electronic and optoelectronic devices based on two-dimensional (2D) materials. In this paper, we examine the quantum confinement and phonon anharmonicity of different-layered MoS 2, synthesized via the chemical vapor deposition technique. We explore the contribution of spin–orbit and interlayer couplings both theoretically (first-principles density functional theory) and experimentally (Raman and photoluminescence spectroscopies). Further, we demonstrate the thermally driven layer-dependent bandgap tunability in (1L, 3L, and 5L) triangular MoS 2 grown over the SiO 2 /Si substrate. We have also scrutinized their phonon confinement behavior and thermal response in a low-temperature regime (80–300 K) using the optothermal Raman spectroscopy technique. A semiquantitative model comprising the volume and temperature effect provides insights into the nonlinear temperature-dependent phonon anharmonicity, revealing that the contribution of higher order (three) phonon scattering reduces with increasing layer numbers in MoS 2 . We further measure the interfacial thermal conductance ( g ) and thermal conductivity ( k s ) of synthesized MoS 2, and the obtained values of g (and k s ) are observed to increase (and decrease) with increasing layer number. Our study will advance the understanding of anharmonic behavior of phonons in different-layered MoS 2 nanostructures for designing MoS 2 -based next-generation devices for various applications.