Cold cathode electron emission with ultralow turn-on fields from Au-nanoparticle-decorated self-organized Si nanofacets

Abstract

Fabrication of highly dense conical nanostructures and their subsequent controlled metallization make them ideal candidates for enhancing cold cathode electron emission efficiency. For instance, hierarchical growth of self-assembled noble metal nanoparticles on self-organized nanostructured materials offers the advantage of fabricating low threshold cold cathode electron emitters. However, the fabrication of stable Si nanostructure-based cold cathode electron emitters with ultra-low threshold fields is a challenging task. This report presents cold cathode electron emission from Au-NP-decorated ensembles of self-organized silicon nanofacets (Si-NFs) having fascinating ultralow turn-on fields (as low as 0.27 V μm⁻¹) and remarkably low threshold electric fields (as low as 0.37 V μm⁻¹) with outstanding stability. It is interesting to note that even as-prepared Si-NFs offer hitherto unseen low turn-on fields (as low as 0.58 V μm⁻¹) and threshold electric fields (0.66 V μm⁻¹) – so far as silicon-based nanostructures are concerned. Kelvin probe force microscopy studies reveal that tunability in the work function of Au-NP-decorated Si-NF samples depends on the dimension and growth-angle of gold nanoparticles (Au-NPs). In addition, in-depth dual pass tunnelling current microscopy measurements demonstrate that the Au-NPs on the apexes and sidewalls of Si-NFs act as cold cathode electron emission sites which help to improve the turn-on and threshold fields for Au-NP-decorated Si-NFs in comparison to their as-prepared counterparts where electron emission takes place mostly from their sidewalls and valleys. Furthermore, finite element electrostatic field-based simulations reinforce the experimental observations. The present investigation paves the pathway to the fabrication of self-organized Si nanostructure-based highly stable cold cathode electron emitting devices having fascinating low turn-on and threshold fields along with extremely high field enhancement factors and high stability for use in nanoscale electronic devices.