Fabrication of Nanopore Array Electrodes by Focused Ion Beam Milling

• Published in: Analytical chemistry (Washington) Vol. 79; no. 8; pp. 3048 - 3055
• Main Authors: Lanyon, Yvonne H, De Marzi, Gianluca, Watson, Yvonne E, Quinn, Aidan J, Gleeson, James P, Redmond, Gareth, Arrigan, Damien W. M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-04-2007
• Subjects: Analytical chemistry; Chemistry; Diffusion; Electrochemical methods; Electrodes; Exact sciences and technology; Ion beams; Scanning electron microscopy; Silicon nitride; Scanning electron microscopy; High resolution; Prototype; Electrochemical method; Silicon nitride; Voltammetry; Nanoporous materials; Steady state; Focused ion beam technology; Electrodes; Transport process; Electrochemical properties; Platinum; Imaging; Milling; Diffusion; Mathematical model; Conformation
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac061878x

Single nanopore electrodes and nanopore electrode arrays have been fabricated using a focused ion beam (FIB) method. High aspect ratio pores (∼150−400-nm diameter and 500-nm depth) were fabricated using direct-write local ion milling of a silicon nitride layer over a buried platinum electrode. This local milling results in formation of a recessed platinum electrode at the base of each nanopore. The electrochemical properties of these nanopore metal electrodes have been characterized by voltammetry. Steady-state voltammograms were obtained for a range of array sizes as well as for single nanopore electrodes. High-resolution scanning electron microscopy imaging of the arrays showed that the pores had truncated cone, rather than cylindrical, conformations. A mathematical model describing diffusion to an electrode located at the base of a truncated conical pore was developed and applied to the analysis of the electrode geometries. The results imply that diffusion to the pore mouth is the dominant mass transport process rather than diffusion to the electrode surface at the base of the truncated cone. FIB milling thus represents a simple and convenient method for fabrication of prototype nanopore electrode arrays, with scope for applications in sensing and fundamental electrochemical studies.