Si Nanowire With Integrated Space-Charge- Limited Conducted Schottky Junction for Enhancing Field Electron Emission and Its Gated Devices

摘要

Integrated field emission electron sources with low driving voltage are desired for microano vacuum electronics. Herein, we demonstrate the enhanced and stable electron emission from crystalline gold-silver (Au-Ag) alloy nanoparticle capped Si nanowires (SiNWs) and the achieved gated electron sources with low driving voltage (<50 V). Thermally induced self-assembly hemispherical (50-80 nm) crystalline Au-Ag nanoparticles were prepared and used as masks in plasma etching to form vertically aligned high aspect ratio (similar to 14) SiNWs. The nanoparticles were preserved after the etching, forming in situ integrated Au-Ag/Si junctions with each individual SiNWs. The SiNWs with capped nanoparticles possess superior field emission current density (45.80 mA/cm(2)) and current stability (fluctuation similar to 6%). A self-aligned process was developed to fabricate gated field emission devices, using the Au-Ag nanoparticle capped SiNWs as cathode. The gated devices showed field emission at low gate voltage (69.52- mu A/cm(2) at 42.1 V). Experimental and numerical simulation studies demonstrated the Au-Ag/Si contact behaved as space-charge-limited (SCL) Schottky conduction. The idea behind the enhancing and stable emission is that the SCL-Schottky junction undergoes a process of negative feedback and thus suppressed the current and shot-noise from the outstanding SiNWs. Accordingly, more SiNWs were activated and contributed stable and higher field emission current.