Theoretical modeling of ice lithography on amorphous solid water.

Due to the perfection of the nanofabrication in nanotechnology and nanoscience, ice lithography (IL) by patterning ice thin-films with a focused electron beam, as a significant derivative technology of electron beam lithography (EBL), is attracting growing attention, evoked by its advantages over traditional EBL with respects of -fabrication, high efficiency, high accuracy, limited proximity effect, three-dimensional (3D) profiling capability, . However, theoretical modeling of ice lithography for replicated profiles on the ice resist (amorphous solid water, ASW) has rarely been reported so far. As the result, the development of ice lithography still stays at the experimental stage.

Spectral filter in short-wave infrareds based on a metasurface on silicon-on-insulator with polarizing bandpass.

Spectral filters with polarimetric character in short-wave infrareds are urgently needed because of their broad applications in optic-fiber communications, polarimetric detections, and imaging. Based on our earlier progress in developing polarimetric devices in infrared wavelengths, in this work, a plasmonic-metasurface-based polarization-dependency multi-channel narrowband filter in short-wave infrareds was developed. To meet the requirement by the developing trend of polarimetric detection/spectral imaging in short-wave infrareds, a resonant cavity in the form of the Au hat/elliptical / pillars/Au layer as the filters was proposed.

Optimization study of metallic hole arrays as the multi-channel spectral filters in long-infrared wavelengths.

The development of miniaturized multi-channel infrared filters based on plasmonic metasurfaces is attracting growing attention, driven by its potential applications in infrared imaging, photodetectors, and spectroscopy. However, the advance of such filters in long-infrared wavelengths has rarely been reported. This paper reports our recent progress on developing multi-channel spectral filters based on micrometer metallic hole arrays in the long-infrared band of 10-15 µm.

Optimization study of metallic sub-wavelength gratings as the polarizer in infrared wavelengths.

Despite the polarimetric detection in the infrared wavelengths of 8-10 µm being of great importance and broad applications, there has been limited addressing of the grating-based polarizers in this band. One of the main issues lies in the process incompatibility between the conventional nanofabrication technique and the II-VI materials such as HgCdTe, so that the direct integration of polarizers with sensors still remains a big challenge. This paper reports our recent work on optimizing the grating structures, materials, and nanofabrication processes for enhancing both the transmittance and the extinction ratio of polarizers on Si and/or ZnSe wafers, using numerical simulations for the grating design and electron beam lithography for the nanoscale pattern generation.

Achieving Infrared Detection by All-Si Plasmonic Hot-Electron Detectors with High Detectivity.

An improved architecture for all-Si based photoelectronic detectors has been developed, consisting of a specially designed metasurface as the antenna integrated into a Si nanowire array on the insulator by an electron beam lithography based self-alignment process. Simulation using the Finite Difference Time Domain (FDTD) method was carried out to ensure perfect absorption of light by the detector. Optic measurement shows a 90% absorption at 1.

All-Si Photodetectors with a Resonant Cavity for Near-Infrared Polarimetric Detection.

This work developed an all-Si photodetector with a surface plasmonic resonator formed by a sub-wavelength Au grating on the top of a Si-nanowire array and the same one beside the wires. The Au/Si interface with a Schottky barrier allows the photo-electron detection in near-infrared wavelength based on the internal emission of hot electrons generated by the surface plasmons in the cavity. Meanwhile, the Au sub-wavelength grating on the Si nanowire array acts as a polarizer for polarimetric detection.

Reconstructing a plasmonic metasurface for a broadband high-efficiency optical vortex in the visible frequency.

Metasurfaces consisting of a two-dimensional metallic nano-antenna array are capable of transferring a Gaussian beam into an optical vortex with a helical phase front and a phase singularity by manipulating the polarization/phase status of light. This miniaturizes a laboratory scaled optical system into a wafer scale component, opening up a new area for broad applications in optics. However, the low conversion efficiency to generate a vortex beam from circularly polarized light hinders further development.

High-resolution plasmonic structural colors from nanohole arrays with bottom metal disks.

We present transmissive plasmonic structural colors from subwavelength nanohole arrays with bottom metal disks for scaled-up manufacturing by nanoimprint lithography (NIL). Comprehensive theoretical and experimental studies are carried out to understand the specific extraordinary optical transmission behavior of the structures with such bottom metal disks. Distinctive colors covering the entire visible spectrum can be generated by changing the structural dimensions of hole arrays in Ag covered by the metal disks.

Lithographically-generated 3D lamella layers and their structural color.

Inspired by the structural color from the multilayer nanophotonic structures in Morpho butterfly wing scales, 3D lamellae layers in dielectric polymers (polymethyl methacrylate, PMMA) with n ∼ 1.5 were designed and fabricated by standard top-down electron beam lithography with one-step exposure followed by an alternating development/dissolution process of PMMA/LOR (lift-off resist) multilayers. This work offers direct proof of the structural blue/green color via lithographically-replicated PMMA/air multilayers, analogous to those in real Morpho butterfly wings.

Photon nanojet lens: design, fabrication and characterization.

In this paper, a novel nanolens with super resolution, based on the photon nanojet effect through dielectric nanostructures in visible wavelengths, is proposed. The nanolens is made from plastic SU-8, consisting of parallel semi-cylinders in an array. This paper focuses on the lens designed by numerical simulation with the finite-difference time domain method and nanofabrication of the lens by grayscale electron beam lithography combined with a casting/bonding/lift-off transfer process.

Gold nanopillar arrays as biosensors fabricated by electron beam lithography combined with electroplating.

We report our work on the development of subwavelength gold pillar arrays as local surface plasmonic (LSP) resonators for sensor applications. These arrays are fabricated by electron beam lithography combined with electroplating. The conical shape, instead of flat one, on the top of Au pillars, induced by uneven current density in the plating, may affect the LSP resonance (LSPR).

Patterning the mechanical properties of hydrogen silsesquioxane films using electron beam irradiation for application in mechano cell guidance.

Hydrogen silsesquioxane (HSQ) is a material with the potential for studying the effect of surface stiffness on stem cell differentiation. Here, the effects of electron beam dose on the topography and the mechanical properties of HSQ obtained with or without trimethylamine (TMA) development are characterised by atomic force microscopy imaging and indentation. A correlation between the surface stiffness (uniform across the sample) and electron beam exposure is observed.

A new chemically amplified resist for high resolution patterning by E-beam lithography.

In this work, we have undertaken evaluation of the lithography property of a recently available chemically amplified resist (CAR) resist, UV1116 supplied by Rohm and Haas Company. Systematic study of the EBL property such as sensitivity, contrast, high resolution limit and dense capability, as well as resistance to plasma dry etching has been carried out. In comparison with the performance of UVIII, we conclude that the UV1116 can be a good alternative with better lithography quality.

Fabrication of 150 nm half-pitch grating templates for nanoimprint lithography.

We present the fabrication of 150 nm half-pitch Si grating templates by reactive ion etch (RIE), which are used in nanoimprint lithography (NIL) for high groove density gratings in SU-8 plastic. The etch properties such as the etch rate, profile and etching selectivity of Si over Cr as etch mask were carefully studied. Under the optimum condition Si gratings with 150 nm in linewidth, 480 nm in height and nearly 90 degree in verticality of the sidewall have been achieved.