In situ manipulation of electron beam irradiation-activated nanoscale tips formation from amorphous and metal modified silica nanowires

Abstract

Escalating use of amorphous silica nanowires (a-SiO_x NWs) in potential applications demonstrates the demand of novel processing techniques at nanoscale. Due to the imperfect structure and porous morphology, a-SiO_x NWs can be metal-modified which allows for electrical conduction under visible light. Unfortunately, their brittle nature at room temperature and nanometric-size make it demanding to precisely process and change shape from an elongated fiber to a sharply pointed tip. Here energetic electron beam (e-beam) irradiation of a-SiO_x and a-SiO_x NWs with gold-nanoparticles (Au-NPs) (Au–SiO_x NWs) is performed to develop diverse shaped nanoscale tips by optimizing e-beam parameters. Sharp amorphous tips (6 and 11 nm), extremely sharp Au-tips (4 and 6 nm), and relatively thick (16 and 18 nm) amorphous tips with average lengths of 50, 30, and 20 nm are formed at the centers of a-SiO_x and Au–SiO_x NWs when a tightly focused e-beam with beam spot size (~ 42 nm) equal to the diameters of NWs is centered at their axes and edge positions respectively. Au-tips thickening (4 or 6 to 22 nm) with reduction (20–16 nm) in length is observed when a uniform e-beam with beam spot size ~ 200 nm is employed. In-situ electron microscopy evaluation demonstrates that during e-beam processing, evaporation, diffusion, plastic flow, and dewetting are driven by positive curvature and e-beam activation effect. The combination of beam spot size and position can be used to tailor atomically sharp tips for wide applications, such as interconnects, biochemical sensing, scanning near-field optical microscopes, blue light emitters, and manipulations.