Tunable and Selective Doping Modulation in Pd-Filled Carbon Nanotube Transistors

Doping remains one of the most difficult yet essential processes for single wall carbon-nanotubes (SWCNTs) electronics. The highly stable sp² carbon network makes doping extremely difficult, rendering the development of SWCNTs-compatible doping strategies and reliable doping-control methods particularly challenging. Herein, we establish a controllable doping strategy by combining Pd encapsulation with electron-beam(e-beam) irradiation, enabling precise doping modulation. With this strategy, strong p-type doping introduced by Pd encapsulation can be effectively modulated by acceleration voltage of e-beam, enabling tunable, reversible doping control from lightly doped to heavily doped states. This approach allows the construction of SWCNTs transistors with heavily doped contacts and a lightly doped channel. Compared with pristine SWCNTs device, achieving a contact resistance reduced by half to 23 kΩ µm^-1, an on-current enhanced by about four times to 24 µA µm^-1, and an on/off ratio exceeding 10⁷, providing an effective approach to overcome the challenges of efficient doping in carbon-based electronics.