Polarized Raman study of large built-in strain in monolayer WS2 grown on Au/W substrate

Abstract

© 2022 Korean Physical Society. Strain plays a crucial role in the energy landscape of atomically thin two-dimensional materials. Here, we report polarized Raman results of WS2 monolayers having either rough or wrinkled surface morphologies. For rough WS2, the E′ phonon intensity exhibits polar behavior that deviates from the Raman polarization selection rules. Furthermore, with the formation of wrinkles on the WS2 surface, the E′ phonon splits into E′− and E′+ phonons. Polar plots of the E′− and E′+ phonon intensities as a function of polarization angle θ show that both phonons have strong polar dependence with orthogonal characteristics in their polarized intensity profiles: the E′− phonon intensity is maximum when the E′+ phonon intensity is diminished, and vice versa. Our result demonstrates that built-in strain in low-dimensional materials can be quantitatively identified by polarized Raman studies and further provides a useful strategy to achieve better device performance for which strain engineering is required.