Interdigitated 50 nm Ti electrode arrays fabricated using XeF₂enhanced focused ion beam etching

Abstract

The fabrication of interdigitated titanium nanoelectrode arrays of 50 nm in width and spacing is described in this work. The nanoarrays have been realized using a Ga + focused ion beam (FIB). FIB milling is typically accompanied by redeposition of removed material, which represents an important hindrance for milling closely spaced nanostructures. Redeposition effects have been reduced by means of XeF 2 gas assistance, which increases the etch yield by a factor of seven compared with pure ion milling. Furthermore, we used a simple adsorption model, which led to the conclusion that dwell time and refresh time should be <500 ns and >30 ms, respectively, for optimized XeF 2 assisted Ti milling. The measured resistance R of the electrodes is higher than 1 G .

Focused Ion Beam (FIB) Technology for Micro- and Nanoscale Fabrications

“…The formation of conical pores by FIB milling has been explained to be caused by redeposition of milled material [ 28 , 29 ]. To address this problem, the use of XeF2-enhanced FIB milling is demonstrated to reduce the effects of material redeposition in the fabrication of inter-digitated nanogap nanoelectrodes [ 30 ]. These nanopore arrays produced by FIB were explored by many groups to mimic cell membrane nanopores and for DNA biosensing applications [ 31 ].…”

Top‐Down Approaches to the Fabrication of Nanopatterned Electrodes

“…Moreover, the fabrication step can be monitored in situ by secondary electron images induced by the FIB [33]. One of the principal applications of FIB is the physical sputtering of material by ion impact for micro-and nano-patterning [35].…”

“…The FIB milling technique has been used to create recessed nanopore and nanoband electrodes on oxidized silicon wafer substrates [35,36]. Platinum electrodes (100 nm thick, and typically microbands of 2 mm · 0.6 mm) were initially fabricated using UV lithography, metal deposition and lift-off processes.…”

“…The FIB lithography approach has also been used to create interdigitated titanium nanoelectrodes by Santschi and coworkers [35]. In this case, photolithography and plasma etching of a silicon-based wafer to create bond pads for the nanoelectrodes were initially conducted.…”

“…The nanoelectrodes were 1 mm bands in length with 50 nm band widths and 50 nm band gaps. Although complete electrochemical characterization of the interdigitated nanoelectrodes was not conducted, the resistance between adjacent electrodes was higher than 1 GO, and thus was reported to be suitable for a wide range of applications [35]. Nagase and coworkers [38] have also used FIB lithography to create nanoelectrode structures with nanogaps, which are becoming an increasingly popular means of creating electrode structures of comparable size to single molecules (see Section 3.3.4).…”