Non-local Molecular Engineering Modulates Aluminum-Induced Crystallization toward Transferable Polycrystalline Silicon

Low-temperature metal-induced crystallization (MIC) has emerged as a promising and cost-effective technique for fabricating polycrystalline silicon (poly-Si), which is a key material in high-performance flexible electronics. However, conventional MIC often yields structurally compromised films due to chaotic interfacial thermodynamics and incomplete layer exchange. Herein, a molecular-level engineering strategy is presented that utilizes buried self-assembled monolayers (SAMs) to remotely control the macroscopic phase transformation and crystallization kinetics during MIC with aluminum as the metal. By systematically tailoring the terminal functional groups of the SAMs at the buried interface between the Al/Si stack and substrate (glass), a distinct structure-property relationship is established: electron-withdrawing groups intrinsically stabilize the amorphous Si (a-Si) network and suppress segregation, whereas electron-donating groups facilitate silicon dissolution. Notably, the best-performing SAM with nucleophilic -NH2 terminal groups functions as a dual-role molecular template that drastically lowers the macroscopic crystallization barrier of the MIC system. By driving a highly directed and accelerated kinetic pathway, this monolayer substantially suppresses stochastic interdiffusion, yielding a highly segregated, continuous, and transfer-ready poly-Si film. Ultimately, this SAM-mediated paradigm advances the fundamental design of non-local phase transformations, establishing a scalable, material-driven pathway for next-generation flexible silicon electronics.