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Based on surface plasmon resonant enhancement, a method to realize photolithography beyond diffraction limit by using polystyrene spheres (PSs) self-assembled on silver slab was proposed in this paper. The optimum parameters for PS with different diameters were presented. In order to verify this method, numerical simulation on a typical configuration with 1.5 microm diameter of PS was carried out by using the finite-difference time-domain (FDTD) method, and the minimum feature size of 88 nm beyond diffraction limit at 365 nm working wavelength was obtained.

Specific protein detection in multiprotein coexisting environment by localized surface plasmon resonance (LSPR) biosensor is studied. After the surfaces of self-assembly fabricated triangular Ag nanoparticles on the chip are activated, a specific biological molecule layer with \delta-toxic protein identifying function is linked to the chip. Based on the LSPR spectrometer measurement system in our laboratory, \delta-toxic protein in sonicated Bacillus thuringiensis cell fractions (which consists of many kinds of proteins) is detected successfully by measuring the extinction spectrum of the chip. [ABSTRACT FROM PUBLISHER]

Abstract: A biochemistry nanosensor was put forward on the basis of a new structure: hybrid metallic nanostructure array (spherical and pyramidal-shaped nanoparticles) in this paper. The hybrid metallic nanostructure array consists of two types of Ag nanostructures: spherical and pyramidal structures patterned with the same period. Design, fabrication and characterization of the Ag nanostructures were presented. Relevant experimental results were obtained by means of detecting the transmittance spectra of the hybrid metallic nanostructure. Apparent shifting of peak wavelength of the transmittance spectra occurs while varies the periods and the effective refractive index of surrounding mediums. Moreover, there are some sharp and narrow peaks of the transmittance spectra by which it can improve the resolving power of the biochemistry nanosensor. [Copyright &y& Elsevier]

We present a calculation model to investigate the focusing characteristics of an atomic beam in a laser standing wave, taking the wave nature of the atomic propagation into account. The effects of atom source, optical parameters of the laser field and the substrate position on atom focusing are analyzed. Numerical simulations indicate that the best focusing performance can be obtained by repositioning the substrate or optimizing the longitudinal atomic beam speed, laser intensity and the detuning of the laser beam. The feature width of the nanostructure is mainly determined by the transverse speed distribution of atoms. Some methods for optimizing experimental parameters are suggested. [ABSTRACT FROM AUTHOR]

The spatial distribution of the interference of surface plasmon polariton (SPP) on metallic nanostructures has been studied. The results show that the transmission of electromagnetic radiation is remarkably enhanced for frequencies close to the surface plasmon band and the interference of SPP can redistribute the illumination light into subwavelength-scale spatial distribution with high intensity, which beats the Rayleigh diffraction limit. For an appropriate thickness, the transmission of an unperforated structure can be larger than that of holes or slits systems with the same periodicity and thickness when the coupled surface plasmon wave mode is excited. With the help of the interference of the horizontal plasmon excited by Bragg resonance due to the periodicity in the horizontal direction, the vertical plasmons, excited in z direction via Fabry–Perot cavity resonance in different grooves, are correlated, so the transmission is increased via the tunneling process. The properties of transparency for light but impenetrability for gas and liquid will be of importance for device applications. The information on near-field distribution from perforated metallic structures is important for understanding the underlying physics, as well as for optimizing photonic crystals for possible applications. [ABSTRACT FROM AUTHOR]

In this study, double-sided polymer surface nanostructures are fabricated using twice nanoimprint lithography and metal deposition technique. We perform electrical property measurement on these double-sided surface nanostructures. Open-circuit voltage and short-circuit current of the as-prepared samples with double-sided surface nanostructures and conductive electrode are recorded using an oscilloscope with applying different external force. The measurements are carried out at room temperature. We find that the intensity of open-circuit voltage and short-circuit current for the double-sided surface nanostructures depends strongly on the sizes, shapes, and arrangements of nanostructures and pressure force. The strongest electrical property can be observed in the hexagon nanopillar arrays with the diameter of about 400 nm containing sub-50-nm resolution sharp structures at the force of about 40 N. We discuss the physical mechanisms responsible for these interesting research findings. The experimental results we study are relevant to the applications of double-sided surface nanostructures such as a nanogenerator, pressure sensors, and nano-optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract: We report a method of fabricating metal nano-grating by Solid immersion Interference lithography based on Backside exposure technique (SIB). Solid immersion lithography can improve the resolution of interference patterns by a factor of n (refractive index of prism), and backside exposure technique can improve the energy utilization ratio and protect the surface of the resist from being contaminated. In the process of fabrication, a high quality sacrificial layer (dielectric grating with high modulation depth and appropriate duty ratio) is important for transferring the patterns to the metal film. We optimized the exposure/development time by simulating the process of backside exposure. Simulation and experiment results show that: using 441.6nm wavelength laser, a series of subwavelength patterns (used as sacrificial layer) with high modulation depth and appropriate duty ratio can be gotten, the feature size of the patterns can be down to 80nm which is less than 0.18λ. Using optimized condition, high quality sacrificial layer can be achieved by using the backside exposure technique. Backside exposure technique has a greater exposure/development time tolerance for fabricating nano-patterns than the conventional interference lithography, which can be used for nano-metal grating fabrication. [Copyright &y& Elsevier]

Abstract: We propose to use two-dimensional metal hole-array (TMH) and spatial light modulator (SLM) technology to construct a parallel direct-writing system. SLM and movable platform are used to control the system for realizing multi-beam parallel scanning exposure to fabricate arbitrary patterns. In this system TMH is the key component which focuses the incident light beams into light spots in the photoresist by exciting local surface plasmon polariton (LSPP). Parameters of TMH are optimized to improve the focusing efficiency and transmission depth of the light spots. Theoretical analysis and numerical simulations show that the feature size and transmission depth can reach sub-80nm and 90nm, respectively, by an optimized TMH, which is feasible for parallel direct writing lithography. [Copyright &y& Elsevier]

Abstract: We have preformed finite-difference time-domain (FDTD) analysis of surface-plasmon polaritons (SPPs) interference nanolithography based on end-fire coupling method. The simulated results show the interference of two face-to-face SPPs can fabricate an 80nm periodicity pattern at the incidence wavelength of 365nm, which surprisingly has long decay lengths for transverse and longitudinal directions and are insensitive to the focusing and alignment conditions. [Copyright &y& Elsevier]

Abstract: We propose a method of generating nanostructures based on evanescent waves coupling. The nanopatterns with ultra-high resolution can be formed by the interference of the evanescent waves between the pattern edges of the mold. Through properly adjusting the width of the mold groove, critical dimension of the nanopatterns can be effectively controlled. The critical dimension of the electric field versus the width of the mold groove is systematically calculated by finite-difference time-domain method. The calculation results demonstrate that through adjusting the geometric parameters of the mold, critical dimension of the electric field can be controlled within the range of 30nm and 100nm, and the contrast ratio is above 60%. This method provides an easy way for fabricating nanostructures with various dimensions corresponding to the mold patterns and it maybe useful in the applications such as integrate circuits, ultra-high sensitive sensors, and optical storage. [Copyright &y& Elsevier]