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Nanoimprint lithography (NIL) technology has aroused great interests in both academia and industry due to its high resolution, low-cost, and high-volume nanopatterning capability. And as an expoxy resin-based negative amplified photoresist, SU-8 is an ideal candidate for NIL because of its low-glass-transition temperature, low-volume shrinkage coefficient, and good optical properties. In this reviewing paper, we highlight the major technical achievements in NIL on epoxy resin and its applications for bio- and nanophotonic structures. NIL was also applied for the duplication of imprint templates, originally fabricated by e-beam lithography (EBL) followed by reactive ion etch (RIE), using a SU-8/SiO2/PMMA tri-layer technique. And nanoimprint properties were systematically investigated for optimization. The developed nanoimprint process for different applications indicates promising industrial potentials in the next generation lithography resolution. [ABSTRACT FROM AUTHOR]

Abstract: Nanoscale PZT gratings are successfully transferred to a Pt substrate using reversal nanoimprint technique without any chemical etch processes. The transfer process is preliminarily studied by measuring the surface topography of PZT coated on templates before transferring as well as the transferred patterns on substrates. Piezoelectric force microscopy (PFM) and Raman spectroscopy are used to investigate the transferred PZT nanostructures after annealing. Good ferroelectric and structural properties have been demonstrated by the transferred PZT nanostructures, indicating that this reversal imprint technique is applicable for forming nanoscale PZT domains, which may lead to the manufactures of high density data storage devices at economic cost. [Copyright &y& Elsevier]

Abstract: In this work the interaction between the metallic planar chiral metamaterials (PCM) with complementary rosette pattern and the incident electromagnetic wave was studied theoretically using finite difference time domain (FDTD) method. Both the evolution of the electric field distribution as the electromagnetic wave propagated through this PCM and the optic activity in near infrared range were investigated. By utilizing nanoimprint lithography technology, we successfully fabricated metallic PCM with complementary rosette pattern with period of 600nm. The measurement results of polarization rotation capability indicate that by easily tuning the depth of the imprint depth in SU-8, the optical activity of this metallic PCM could be effectively controlled for specific wavelength. [Copyright &y& Elsevier]

Abstract: In this work, we demonstrate the fabrication of silicon nanowires down to 22nm wide using trilayer nanoimprint lithography and wet etching. Using the same template prepared by E-beam lithography (EBL), nanowires with top width of 22nm and 75nm are fabricated on boron-doped top silicon layer of SOI substrate. The two samples are tested in 250ppm NO2 ambient for gas detection. The 22nm wide one shows a much higher relative sensitivity than the 75nm wide one. The simulation which calculates the carrier density by solving Poisson equation was carried out and the results well explain the sensitivity disparity between the two samples. [Copyright &y& Elsevier]

Abstract: We demonstrate the nanofabrication of the transmission SU-8 gratings with periods from 200nm (5000lines/mm) to 1μm (1000lines/mm) with different trench depths for applications from near-infrared to deep-UV wavelength. The imprint property of SU-8 under various pressures and temperatures was systematically studied and agreed well with the simulation results. The effects of trench depth on diffraction intensity profiles were simulated and results show periodic diffraction orders with varying intensity distributions, which is in good accordance with the results from optical measurements. The high optical transmittance of SU-8 in the visible range and its low volume shrinkage coefficient make the developed process an ideal candidate for high-volume manufacturing of various gratings at low cost. [Copyright &y& Elsevier]

• 45-170 nm wide NiSi nanowires are formed by Ni and Si nanowire solid-state reaction. • Ni quantity on Si nanowire sidewalls needs to be controlled to get NiSi phase. • Nickel silicide nanowire growth is square root time dependent with Ea of 1.66 eV. The linewidth related resistivity variation and growth behavior of nickel silicide nanowires by solid state reaction between Ni and Si nanowires are studied. 44 nm Ni is sputtered onto Si nanowires to form nickel silicide nanowires by rapid thermal annealing at 500°C, and the resistivities of formed nickel silicide nanowires are located in the range of 13.8-22.3 μΩ•cm for nanowires with linewidths larger than 80 nm (83-170 nm), while the resistivities rise to 39-125 μΩ•cm for the nanowires with linewidths of 30-80 nm. Multiple measurement results have shown that the resistivity increase is resulted from the formation of high resistivity Ni-rich phase (Ni 3 Si 2 for nanowire with linewidth of 70 nm), which is closely related with the excessive Ni deposited on Si nanowire sidewalls. By using electron beam evaporation in place of sputter deposition, the Ni amount on the Si nanowire sidewalls has been reduced and the resistivities can be also in the range of 13.8-22.3 μΩ•cm for nanowires with linewidths of 45-80 nm. The length of nickel silicide nanowire shows square root dependence on annealing time, indicating a diffusion controlled growth with activation energy of 1.66 eV. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present a waveguide-surface plasmon resonance biosensor. A 450nm period sub-wavelength metallic gratings (SWMGs) were fabricated by nanoimprint, which was then applied to detect the protein layer capping on the grating. Both our measurement and simulation results indicate that the resonance does exist for 450nm pitched gratings. A resonance shift in surface plasmon resonance (SPR) curves of protein films with different refractive indices were investigated, which would be promisingly applied in protein, DNA or drug test. Moreover, a novel angle of incidence (AOI) based detection method was developed to help reduce the cost of the expensive detecting devices. [Copyright &y& Elsevier]

Abstract: In this paper, we present the nanofabrication of a potentially coupled waveguide–surface plasmon resonance biosensor (CWSPRBs) by nanoimprint lithography. Subwavelength metallic gratings (SWMGs) with the pitches of 300 and 500nm were fabricated by direct imprinting on PMMA layer which subsequently covered with a layer of Au. The key issue in this device is the coupling of surface plasmon with waveguide modes, which has been carefully investigated by measuring the coupling induced enhancement of light transmission. Both our measurement and simulation results indicate that the resonant coupling does exist for both 300 and 500nm pitched gratings. This proves that the developed nanoimprint lithography is applicable for the CWSPRBs sensors which has significant advantages over traditional ones with a prism. [Copyright &y& Elsevier]

Abstract: In this paper, large area nanoimprint lithography on a trilayer resist stack for the nanofabrication of light polarizer was successfully carried out. Large area gratings with 10mm×10mm area and 300nm pitch were fabricated. The measurement results indicate that our polarizers exhibit extraordinarily high extinction ratio. It is observed that the extinction ratio is dependent on the wavelength. Theoretical simulation also agreed with our measured results very well. The poor reflective polarization property measured in this work was discussed. [Copyright &y& Elsevier]

Abstract: Poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), copolymer films nanostructures are attracting increasing interests for potential applications in FERAM, NEMS and sensors. In this work we apply hot embossing lithography to fabricate P(VDF-TrFE) copolymer nanostructures and investigate the influence of this patterning process on the material and electrical properties by using AFM, XRD, FTIR and Precision Ferroelectric Tester. It was found that nano-embossing technique offers not only a low-cost and effective way to fabricate nanoscale structures but also a way to control the orientation and crystal quality of P(VDF-TrFE) films. The electrical measurement also indicated superior ferroelectric characteristics for the imprinted structure to the un-imprinted area of P(VDF-TrFE) films. [Copyright &y& Elsevier]

Abstract: Optic fluidic devices, which combine optical elements such as adaptive optical lenses or diffraction gratings into micro-fluidic devices, are now becoming increasingly important for environmental monitoring, medical diagnostics and chemical detection. In this paper, we present a novel and simple micro/nanofabrication process for SU-8 based optic fluidics structures with phase gratings on the bottom of the micro-channel using our silicon grating templates. The refraction index difference between the fluid and the SU-8 gratings generates a modulation in the phase of the light passing through the device. Our method of fabricating optic fluidic device is promising to be economic in fabrication, high throughput in production and have potential applications for sensing. [Copyright &y& Elsevier]

Abstract: We report a novel nanoprocess combining nanoimprint lithography and conventional lithography to fabricate metallic and dielectric nanophotonic crystals with chiral elements in SU-8. The previously developed nanoimprint process was modified for much smaller feature size. Four different types of nanophotonic crystals with different materials in both large and small dimensions are fabricated. The new proposed reversal lithography is used to fabricate one type among the above mentioned four. The success of reversal lithography provides a solution for near-field lithography to achieve nanosize structures with simple conventional lithography. Optical measurements of the laser polarization state from the fabricated photonic crystals indicate an optical chirality which distinguishes the chiral elements from other normal symmetric structures. [Copyright &y& Elsevier]