Fabrication of microbowtie structures for optical probing of nanoscale objects

A microbowtie array critical to a newly proposed optical probe is studied. The optical probe is used for high-speed detection of nanoscale objects. Based on the concept of Wave Interrogated Near Field Array (WINFA), an array of microbowtie structures acts as a detector in amplifying the incident light source to overcome the difficulties of the conventional optical probe that are limited by the diffraction limits of the optical light. In the present study, the micro bowties are fabricated by an electron beam lithography technique. The paper begins with an introduction of the probe concept and then the design considerations are given followed by the fabrication procedure and results. Two different substrates are considered to study the charge accumulation problem caused by an insulating substrate, required by the probe. Results indicate that the bowtie structure with an indium-tin-oxide coated glass substrate can minimize the charge accumulation problem, making it a suitable substrate for the bowtie structures considered. The paper concludes with recommendations for making even smaller nano-sized bowtie structures.