Direct fabrication of nano-gap electrodes by focused ion beam etching

• Published in: Thin solid films Vol. 499; no. 1; pp. 279 - 284
• Main Authors: Nagase, Takashi, Gamo, Kenji, Kubota, Tohru, Mashiko, Shinro
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 21.03.2006; Elsevier Science
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Electronics; Exact sciences and technology; Focused ion beam; Maskless fabrication; Materials science; Molecular electronic device; Molecular electronics, nanoelectronics; Nano-gap electrode; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Maskless fabrication; Nano-gap electrode; Molecular electronic device; Focused ion beam; Scanning electron microscopy; Gold; Voltage current curve; Film; Nanoparticle; Multiple layer; Transition metal; Electrode material; Experimental study; Adhesion; Molecular electronics; Colloidal suspension; Titanium; Ion beam etching; Nanostructured materials
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2005.07.031

A simple approach to increase the reliability of nano-gap electrode fabrication techniques is presented. The method is based on maskless sputter etching of Au electrodes using a focused ion beam (FIB) and in-situ monitoring of the etching steps by measuring a current fed to the Au electrodes. The in-situ monitoring is crucial to form nano-gaps much narrower than a FIB spot size. By using this approach, gaps of ∼3–6 nm are fabricated with the high yield of ∼90%, and most of the fabricated nano-gap electrodes showed high resistances of 10 GΩ–1 TΩ. The controllability of the fabrication steps is significantly improved by using triple-layered films consisting of top Ti, Au, and bottom adhesion Ti layers. The applicability of the fabricated nano-gap electrodes to electron transport studies of nano-sized objects is demonstrated by electrical measurement of Au colloidal nano-particles.