A Cascade Electron Source Based on Series Horizontal Tunneling Junctions

On-chip tunneling electron sources have wide potential applications in miniature vacuum electronic devices, and emission efficiency is one of their performance benchmarks. A cascade electron source (CES) based on series metal–insulator–metal horizontal tunneling junctions (HTJs) is proposed, where free electrons are additively extracted from each tunneling junction. A CES with
${n}$
HTJs shows a theoretical emission efficiency of approximately
$\eta {(} {n} {)}={1}-{(} {1}-\eta _{{0}} {)}^{n}$
, with
$\eta _{{0}}$
being the efficiency of a single tunneling junction. Experimentally, a CES with three Si–SiO
_x
–Si tunneling junctions is demonstrated, achieving an emission efficiency of as high as 47.6%. This work provides a new way of realizing highly efficient on-chip tunneling electron sources.