Yifei Mao

Focused-Ion-Beam Induced Rayleigh-Plateau Instability for Diversiform Suspended Nanostructure Fabrication

A novel method for fabricating diversiform suspended nanostructures is reported. The method utilizes focused-ion-beam (FIB) induced material redistribution and Rayleigh-Plateau instability, which determine the resulting shapes of formed nanostructures. By choosing target materials, their predefined patterns as well as FIB settings, we have achieved parallel nanofabrication of various kinds including nanostrings, nanobead chains and nanopore membranes with smooth surfaces due to the self-perfection effect of the material redistribution upon the minimization of system free energy. The diameters of the nanostrings and nanopores reach about 10 nm and 200 nm, respectively. The average period of the nanobead chains is 250 nm.

Programmable Bidirectional Folding of Metallic Thin Films for 3D Chiral Optical Antennas

3D structures with characteristic lengths ranging from nanometer to micrometer scale often exhibit extraordinary optical properties, and have been becoming an extensively explored field for building new generation nanophotonic devices. Albeit a few methods have been developed for fabricating 3D optical structures, constructing 3D structures with nanometer accuracy, diversified materials, and perfect morphology is an extremely challenging task. This study presents a general 3D nanofabrication technique, the focused ion beam stress induced deformation process, which allows a programmable and accurate bidirectional folding (-70°-+90°) of various metal and dielectric thin films. Using this method, 3D helical optical antennas with different handedness, improved surface smoothness, and tunable geometries are fabricated, and the strong optical rotation effects of single helical antennas are demonstrated.

Plasmonic scattering resonance enhancement in nanocavity resonators for broad-gamut palettes

We report a type of plasmonic palettes formed by an array of cross-shaped cavity nanostructures for multicolor image generation. And the nanocross-shaped antennas actually act as plasmonic cavity resonators and could realize surface plasmon excitation, resonating and coupling, which can impart intriguing optical properties. These features enable the nanotexted metasurfaces to implement full-gamut palettes through spatially color blending and continuously tunable coloration. We also employ the dark-field scattering and near-field scanning analysis to experimentally study the circularly nanoscale optical scattering in the new cavity-nanopin photonic metasurfaces resulting from aperiodic Fibonacci spiral arrangements.

A green chemistry synthesis of AG nanoparticles and their concentrated distribution on PDMS elastomer film for more sensitive SERS detection

This paper reports a simple and convenient method to fabricate a surface-enhanced Raman scattering substrate. It includes a green chemistry synthesis of Ag nanoparticles(NPs) and a process of coating a monolayer of the Ag NPs on a polydimethylsiloxane(PDMS) elastomer film. Ultra-low concentration of Ag+(10−8M) was used in Tollens method to synthesis monodisperse and relatively uniform Ag NPs. With recovery of the stretched PDMS film, the distribution of Ag NPs gets concentrated, resulting in an improvement of SERS detection sensitivity. Due to the transparent and flexible property of this highly sensitive SERS substrate, it exhibits great potential in in-situ detection of solid or irregular objects.

Randomly controlled metamaterial modulator for dynamic tuning of optical property

We design and fabricate a randomly controlled metamaterial modulator (RCMM) which can dynamically tune reflection in infrared region. The RCMM is a metamaterial-cell array, and each cell is comprised of a raw of S-shaped cantilevers called meta-molecules. The devices were produced by using focused-ion-beam etching and deposition on suspended metal-dielectric-metal membranes. Word/bit-line method is introduced to precisely control the thermoelectricity-caused bending of every individual meta-cell in the RCMM. A 2×2 RCMM exhibits 16 different states, which represents different operation conditions of the device, resulting in the shift of the reflection spectrum. The end portion of a meta-cell with 20 μm-long meta-molecules can be raised up to 2μm, and the corresponding optical reflection of the device will be modulated by up to 40%.

Nanosolenoid inductor for high frequency application

This paper reports the fabrication, measurement and discussion about the nanosolenoid inductors for high frequency applications as much as 40 GHz, taking advantage of a much smaller size compared with traditional microinductors. Three small size nanosolenoid inductors are fabricated, such as a nanosolenoid inductor with a diameter of 4.8 μm, pitch of 10 μm, length of 22 μm. The nanohelix inductors are fabricated using focused ion beam stress introducing technology based on nanobeams, which are obtained by etching the aluminum deposited on SOI substrate. With different focused ion beam fabrication conditions, such as implementing does, etching number, we get different sets of nanosolenoid inductors with different pitches, diameters and solenoid turns. The inductor and quality factor of the nanohelix inductor vary with frequency. The inductanc decrease from 9 pH to an inductance smaller than 1 pH, when the frequency changes from 100 MHz to 40 GHz. And the quality factor of the nanosolenoid inductor first arises from 0.1 at 100 MHz to 0.3 at about 2 GHz, then the quality factor slightly decreases, at last it will arise to about 1.4 at 40 GHz.

Analysis of microhelix inductors with focused ion beam

This paper describes a microhelix inductor structure fabricated with focused ion beam(FIB) stress introducing technology(SIT). With the decrease of the implantation does, the pitch and the diameter of the microhelix inductors decreases, which will also affect the performance of the microinductors. Microhelix inductors with different scales are fabricated from 120 nm thick, 2 um wide, 41um long aluminum microbeams, which are built on SOI substrate. The solenoid microinductor is fabricated with implantation does 2.83×1017cm-2. With different scales of microbeams and fabrication does, we get a microsolenoid inductor with pitch 6 um, diameter 2.3 um. So under the control of different FIB condition, we can get the desired microhelix inductor with needed pitch, diameter and turn number. The fabrication process is controllable and repeatable. We get the S parameters of the microhelix with the help of Agilent network analyzer from 100 MHz to 40 GHz at an interval of 50 MHz, after open structure and through structure deembedding process, the calculated inductance is as small as 10-4 nH, Quality factor arises from 0.02 to 0.55 when the frequency arises from 100 MHZ to 40GHZ respectively.