Direct Growth and Integration of Silicon Nanowire Transistors on Polymer Substrates

The direct low-temperature synthesis of crystalline silicon nanowires (c-SiNWs) on flexible polymer substrates remains a critical yet unrealized milestone for scalable flexible thin-film transistors (TFTs), hindered by the interfacial mechanical mismatch between rigid silicon and deformable polymers and the ultralow thermal budgets imposed by the flexible substrates. Though nanoscale SiNW channels can be patterned/grown and transferred onto polymer substrates, high-precision postgrowth transferring and alignment of these tiny SiNW channels remain technically difficult or too cost-intensive for the implementation of large-area electronics. Here, we demonstrate a direct growth of orderly c-SiNW channels upon a flexible polyimide (PI) film for the first time, through an in-plane solid-liquid-solid (IPSLS) mechanism at 200 °C, achieving uniform diameters of 44 ± 5 nm. The prototype flexible SiNW TFT can endure a bending radius of 6.5 mm for 10,000 cycles, while achieving a high I_on/I_off current ratio of ∼5 × 10⁵, working stably in an ambient environment over 10 months without any passivation protection. These results represent the first experimental evidence that c-Si electronics can also be grown and integrated upon low-cost flexible substrate, opening a straightforward routine to harness the mature and stable c-Si device performance for future flexible electronics, optoelectronics.