Lateral Scaling Effects on Thermal Transport in Suspended Bilayer WS 2 Nanoribbons

As transistor scaling enters the post‐Moore era, two‐dimensional van der Waals semiconductors such as WS 2 are promising channel materials, yet heat dissipation under aggressive lateral scaling and 3D integration remains a major challenge. Here, we experimentally reveal strong width‐dependent thermal conductivity, κ , in suspended bilayer WS 2 nanoribbons synthesized via vapor–liquid–solid growth. Using a refined transfer process, we measure nanoribbons with widths of 156–788 nm and observe that κ increases from 31.9 to 66.2 W m − 1 K − 1 at 300 K, demonstrating pronounced phonon‐boundary scattering under lateral scaling. Callaway‐Holland analysis attributes this size effect primarily to low‐frequency phonons with long mean free paths. Despite this strong size effect, WS 2 maintains κ more than an order of magnitude higher than comparably scaled Si nanostructures. Thermal simulations of vertically stacked nanosheet gate‐all‐around (GAA) transistors further demonstrate that WS 2 channels suppress hot‐spot formation and yield more uniform temperature distributions than Si under identical operating conditions. These findings identify lateral‐size‐controlled phonon transport as a critical design dimension and establish ultrathin WS 2 as a thermally robust channel material for post‐Moore nanoelectronics.