Optimization and performance enhancement of single island carbon nanotube electron beams for microscopy application

This study explores the influence of island diameter, shape, and emitter density on the performance of vertically aligned carbon nanotube (VACNT) cold cathodes for high-resolution electron microscopy applications. VACNT arrays with varying island diameters (small, medium, and large) and shapes (hexagonal and square) were fabricated to evaluate their impact on electron field emission. The effect of increasing emitter density within a fixed area was also analyzed. Smaller island diameters produced stronger localized electric fields, enhancing current density, while hexagonal shapes provided better beam focusing with reduced divergence. Increased emitter density improved total current output and emission stability. Optimized electron beam emission currents of 650 and 120 μA were achieved for diode and triode structures, respectively, using a hexagonal design with 19 emitters and a 23 μm diameter. The optimized emitters demonstrated exceptional performance, with a high current density of 1.2 × 106 A/m2 and a beam brightness of 1.8 × 108 A/m2 sr V. Additionally, the emitters exhibited a minimal beam divergence angle of 1.02°, ensuring precision and focus on electron beam applications. These results highlight the potential of the developed electron beam system for advanced applications requiring high-intensity, stable, and precise electron sources. These findings underscore the importance of optimizing geometric parameters to enhance electron beam performance, advancing VACNT-based electron sources for microscopy and other precision technologies.