Atomic-level boron doping enhances the field emission properties of carbon nanotubes for high-current density X-ray sources

초록

We prepared boron (B)-doped carbon nanotubes (CNTs) for use in field emission (FE) applications that require a high current density (J), such as computed tomography scanners and microwave amplifiers. Although pristine CNTs exhibit superior FE capabilities, they are susceptible to structural degradation under high-current conditions. We used strategic B-doping to address this challenge. B-doping significantly enhanced the thermal stability and FE efficiency of CNTs. Density functional theory calculations revealed that B-doping induced charge redistributions near substitutional defect sites, thereby changing the local electrostatic potential, which significantly amplified the FE current. A direct current arc discharge (DC-AD) method afforded controlled B-doping with preservation of CNT structural integrity. B-CNT emitters exhibited an impressive emission current of 52.4 mA, which corresponds to J of 5.2 A/cm2 at an electric field of 9.8 V/mu m. This performance was sustained over 24 h, maintaining a target J of 1 A/cm2, showcasing the remarkable emission stability. In terms of X-ray applications, a B-CNT-based X-ray tube endured 200,000 shots at a high J of 1.25 A/cm2, demonstrating its robustness and potential for high-dose X-ray generation. Our findings emphasize that B-CNTs serve as valuable materials for next-generation FE applications.

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