Au/ITO dual-layer-coated optical fiber probe for multifunctional scanning tunnelingmicroscopy

Abstract

We have fabricated an Au/ITO (indium-tin-oxide) dual-layer optical fiber probe with functionsfor high-quality scanning tunneling microscope (STM) imaging and near-field excitationand detection of STM-induced electroluminescence (STML). The inner ITO layer is kept∼150 nm in thickness to ensure the conductivity of the fiber probe. The outer Au layer is kept∼13 nm in thickness to obtain a better combination of high electron injection efficiency and opticaltransparency. High-quality STM images, and STML corresponding to maximum quantum efficienciesof 7 × 10−4 and 1 × 10−4 photons/electron are obtained on Au(111)/mica and p-GaAs(110) surfaces at room temperature (RT),respectively. The outer Au layer on the Au/ITO-coated fiber probe shows aneffective role in improving the quality of STM imaging, the tip apex geometryand durability of the fiber probe, the stability and reproducibility of STML andenhancing the intensity of plasmon-mediated STML from the Au(111) surface but itshows no effect in enhancing the intensity of STML from the GaAs(110) surface.