Fabricating ultrathin silicon (Si) channels down to critical dimension (CD) <10 nm, a key capability to implementing cutting‐edge microelectronics and quantum charge‐qubits, has never been accomplished via an extremely low‐cost catalytic growth. In this work, 3D stacked ultrathin Si nanowires (SiNWs) are demonstrated, with width and height of Wnw = 9.9 ± 1.2 nm (down to 8 nm) and Hnw = 18.8 ± 1.8 nm, that can be reliably grown into the ultrafine sidewall grooves, approaching to the CD of 10 nm technology node, thanks to a new self‐delimited droplet control strategy. Interestingly, the cross‐sections of the as‐grown SiNW channels can also be easily tailored from fin‐like to sheet‐like geometries by tuning the groove profile, while a sharply folding guided growth indicates a unique capability to produce closely‐packed multiple rows of stacked SiNWs, out of a single run growth, with the minimal use of catalyst metal. Prototype field effect transistors are also successfully fabricated, achieving Ion/off ratio and sub‐threshold swing of >106 and 125 mV dec−1, respectively. These results highlight the unexplored potential of versatile catalytic growth to compete with, or complement, the advanced top‐down etching technology in the exploitation of monolithic 3D integration of logic‐in‐memory, neuromorphic and charge‐qubit applications.

Catalytic synthesized ultrathin silicon nanowires (SiNWs) are ideal 1D channel materials to fabricate high‐performance transparent and low‐cost thin film transistors (TFTs) that are widely needed for flexible electronics and displays. In this work, a scalable integration of orderly array of SiNW array, with a uniform diameter of only 52 ± 4 nm, grown directly upon glass/wafer substrates, via a guided in‐plane solid–liquid–solid (IPSLS) process, and passivated by a new solution oxidizing/etching cycling technique is demonstrated. This has enabled an all‐low‐temperature (<350 °C) fabrication of high‐performance SiNW‐TFTs, achieving Ion/Ioff current ratio and subthreshold swing (SS) of >106 and 120 mV dec−1 respectively, with excellent negative and positive bias stabilities. Importantly, the SiNW‐TFTs fabricated on glasses with ITO/or metal electrodes demonstrate a high transparency of 90% or 73% respectively, making them ideal candidates for building the next generation of high aperture displays, transparent electronics, and augmented reality applications.

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