<p>Transition metal dichalcogenides (TMDCs) are promising candidates for future nano-transistor channels due to their outstanding intrinsic transport properties. However, their electron mobility is highly sensitive to the surrounding dielectric, often falling well below theoretical expectations. In this work, we explore how a stacked Al<sub>2</sub>O<sub>3</sub> dielectric affects electron mobility in monolayer WS<sub>2</sub> using first-principles quantum transport simulations. We identify that fluctuations in the electrostatic potential, arising from the disordered structure of Al<sub>2</sub>O<sub>3</sub>, significantly degrade mobility, especially when WS<sub>2</sub> interfaces with under-coordinated aluminum atoms. Our calculated mobilities (<span>≃</span>1–30 cm<sup>2</sup>/(V <span>⋅</span> s)) align with experimental observations and remain far from the ideal limit (<span>≃</span>300 cm<sup>2</sup>/(V <span>⋅</span> s)). We further demonstrate that encapsulating WS<sub>2</sub> with hexagonal boron nitride (hBN) or employing a crystalline oxide can recover high mobility values. However, these strategies introduce trade-offs in electrostatic control and fabrication complexity, underlining the need for careful dielectric engineering in TMDC-based devices.</p>
