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

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 '(+)& nbsp;phonon intensities as a function of polarization angle theta 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.