A Cascade Electron Source Based on Series Horizontal Tunneling Junctions

On-chip electron sources have wide potential applications in miniature vacuum electronic devices and emission efficiency is one of their performance benchmarks. A cascade electron source based on series metal-insulator-metal horizontal tunneling junctions is proposed, where free electrons are additively extracted from each tunneling junction. A cascade electron source with n horizontal tunneling junctions 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 cascade electron source with three Si-SiOx-Si tunneling junctions is demonstrated, achieving an emission efficiency as high as 47.6%. This work provides a new way of realizing highly efficient on-chip electron sources.