We demonstrate that bowtie apertures can be used for contact lithography to achieve nanometer scale resolution. The bowtie apertures with a 30 nm gap size are fabricated in aluminum thin films coated on quartz substrates. Lithography results show that holes of sub-50-nm dimensions can be produced in photoresist by illuminating the apertures with a 355 nm laser beam polarized in the direction across the gap. Experimental results show enhanced transmission and light concentration of bowtie apertures compared to square and rectangular apertures of the same opening area. Finite different time domain simulations are used to explain the experimental results.

Nanoscale ridge aperture antennas have been shown to have high transmission efficiency and confined nanoscale radiation in the near field region compared with regularly-shaped apertures. The radiation enhancement is attributed to the fundamental electric-magnetic field propagating in the TE(10) mode concentrated in the gap between the ridges. This paper reports experimental demonstration of field enhancement using such ridge antenna apertures in a bowtie shape for the manufacture of nanometer size structures using an NSOM (near field scanning optical microscopy) probe integrated with nanoscale bowtie aperture. Consistent lines with width of 59 nm and as small as 24 nm have be written on photoresist using such probes.

We report results of parallel optical nanolithography using nanoscale bowtie aperture array. These nanoscale bowtie aperture arrays are used to focus a laser beam into multiple nanoscale light spots for parallel nano-lithography. Our work employed a frequency-tripled diode-pumped solid state (DPSS) laser (lambda = 355 nm) and Shipley S1805 photoresist. An interference-based optical alignment system was employed to position the bowtie aperture arrays with the photoresist surface. Nanoscale direct-writing of sub-100nm features in photoresist in parallel is demonstrated.

Ridge nanoscale aperture antennas have been shown to be a high transmission nanoscale light source. They provide a small, polarization-dependent near-field optical spot with much higher transmission efficiency than circularly-shaped apertures with similar field confinement. This provides significant motivations to understand the electromagnetic fields in the immediate proximity to the apertures. This paper describes an experimental three-dimensional optical near-field mapping of a bowtie nano-aperture. The measurements are performed using a home-built near-field scanning optical microscopy (NSOM) system. An aluminum coated Si(3)N(4) probe with a 150 nm hole at the tip is used to collect optical signals. Both contact and constant-height scan (CHS) modes are used to measure the optical intensity at different longitudinal distances. A force-displacement curve is used to determine the tip-sample separation distance allowing the optical intensities to be mapped at distances as small as 50 nm and up to micrometer level. The experimental results also demonstrate the polarization dependence of the transmission through the bowtie aperture. Numerical simulations are also performed to compute the aperture's electromagnetic near-field distribution and are shown to agree with the experimental results.

C-shaped ridge apertures are used in contact nanolithography to achieve nanometer scale resolution. Lithography results demonstrated that holes as small as 60 nm can be produced in the photoresist by illuminating the apertures with a 355 nm laser beam. Experiments are also performed using comparable square and rectangular apertures. Results show enhanced transmission and light concentration of C apertures compared to the apertures with regular shapes. Finite difference time domain simulations are used to design the apertures and explain the experimental results.