Atomic nanofabrication using an ytterbium atomic beam

Highly parallel and periodically narrow lines of ytterbium (Yb) atoms were successfully produced on a substrate using a near resonant laser light and direct-write atomic nanofabrication. Yb atoms are a promising material for nanofabrication using atom optics particularly due to their electric conductivity, the laser wavelength required for their manipulation, and the vapor pressure required for their fabrication. Collimated ¹⁷⁴Yb atoms were channeled into the nodes of an optical standing wave with dipole force and then deposited onto a substrate. We clearly observed a grating pattern of Yb atoms fabricated on a substrate with a line separation of approximately 200 nm after examining the surface of the substrate with an atomic force microscope. This is the first demonstration of nanofabrication using the atom-optical approach with Yb atoms.     

Atomic nanofabrication using an ytterbium atomic beam

Abstract

Highly parallel and periodically narrow lines of ytterbium (Yb) atoms were successfully produced on a substrate using a near resonant laser light and direct-write atomic nanofabrication. Yb atoms are a promising material for nanofabrication using atom optics particularly due to their electric conductivity, the laser wavelength required for their manipulation, and the vapor pressure required for their fabrication. Collimated ¹⁷⁴Yb atoms were channeled into the nodes of an optical standing wave with dipole force and then deposited onto a substrate. We clearly observed a grating pattern of Yb atoms fabricated on a substrate with a line separation of approximately 200 nm after examining the surface of the substrate with an atomic force microscope. This is the first demonstration of nanofabrication using the atom-optical approach with Yb atoms.     

Recent developments in nanofabrication using ion projection lithography

Ion projection lithography (IPL) is an emerging technology and a major candidate for the next-generation lithography (NGL) designed to complement and supplement current optical lithographic techniques for future chip manufacturing. In this Review, the recent developments of IPL technology are examined with an emphasis on its ability to fabricate a wide variety of nanostructures for the semiconductor industry. Following an introduction of the uniqueness and strength of the technology, the basics of ion-source development and ion-target interactions with and without chemical enhancement are presented. The developments in equipment systems, masks, and resists are subsequently studied. The resolution of printed nanostructures and the corresponding throughput of the current system are assessed for NGL. Finally, concluding remarks are presented to summarize the strengths and weaknesses of the current technology and to suggest the scope for future improvement.     

Recent developments in nanofabrication using focused ion beams

Focused ion beam (FIB) technology has become increasingly popular in the fabrication of nanoscale structures. In this paper, the recent developments of the FIB technology are examined with emphasis on its ability to fabricate a wide variety of nanostructures. FIB-based nanofabrication involves four major approaches: milling, implantation, ion-induced deposition, and ion-assisted etching of materials; all these approaches are reviewed separately. Following an introduction of the uniqueness and strength of the technology, the ion source and systems used for FIB are presented. The principle and specific techniques underlying each of the four approaches are subsequently studied with emphasis on their abilities of writing structures with nanoscale accuracy. The differences and uniqueness among these techniques are also discussed. Finally, concluding remarks are provided where the strength and weakness of the techniques studied are summarized and the scopes for technological improvement and future research are recommended.     

Silicon micro/nanofabrication using metastable helium atom beam lithography

We utilize metastable helium (He*) atom beam lithography to pattern silicon substrates by using self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) grown directly on silicon surface as resist. An improved wet-chemical etching method was used to transfer the resist pattern into silicon substrate. Negative and positive pattern formations with well-defined edges were observed for silicon(100) substrate with SAM after exposure to the He* atom beam followed by the etching. Results indicate a clear transition from positive to negative patterns relies on the He* dosage. The pattern sizes on silicon were successfully decreased to the order of 100 nm, even less than 50 nm.     

Surface patterning for brittle amorphous material using nanoindenter-based mechanochemical nanofabrication

This paper demonstrates a micro/nanoscale surface patterning technology for brittle material using mechanical and chemical processes. Fused silica was scratched with a Berkovich tip under various normal loads from several mN to several tens of mN with various tip rotations. The scratched substrate was then chemically etched in hydrofluoric solution to evaluate the chemical properties of the different deformed layers produced under various mechanical scratching conditions. Our results showed that either protruding or depressed patterns could be generated on the scratched surface after chemical etching by controlling the tip rotation, the normal load and the etching condition. In addition, the mask effect of amorphous material after mechanical scratching was controlled by conventional mechanical machining conditions such as contact area, chip formation, plastic flow and material removal.     

Preparation of protein nanoarray on silicon surface by atomic force microscopy nanofabrication

Atomic force microscopy (AFM) with bias control is employed to fabricate oxidized nanopatterns on a silicon surface with a feature size as low as 50 nm. Nanopatterns made by a Pt/Ir coating probes have larger feature size than these made by the probe without, but the patterning speed is fast, 0.1 s per dot. 20 nm gold nanoparticles are immobilized on oxide nanopatterns to elucidate the dimensions of the nanoparticles on an oxide nanopattern. These patterning conditions are utilized to prepare a nanoarray for the immobilization of biotins to interact with free streptavidins. The resultant height of the biotin labeled on oxidized nanopattern is 0.93 +/- 0.1 nm and the combined height of biotin-streptavidin is 5.14 +/- 0.45 nm, as determined using the imaging functions of AFM. Based on the experimental results, a nano biochip of silicon dioxide can be utilized to monitor molecular interactions on the nanometer scale under static conditions and without the labeling of fluorescence dyes.     

Metal corrosion for nanofabrication

The annual cost of corrosion has been increasing globally, and it has now reached beyond 3% of the world's gross domestic product. It remains a challenge to reduce or prevent unwanted corrosion effectively after many decades of effort. Nowadays, more efforts are being made to develop anti-corrosion platforms for decreasing the huge cost of corrosion. In parallel, it is also highly expected to be able to use corrosion for producing useful materials with reduced energy consumption. In this review, recent progress in how methods for controlling metal corrosion can be used to produce structure-diversified nanomaterials are summarized along with a presentation of their applications. As a valuable addition to the scientists' toolbox, metal corrosion strategies can be applied to different metals and their alloys for the production of various nanostructured materials; this also provides insights into how metal corrosion can be further prevented and into how corrosion wastage can be reduced.     

Electrochemical method for measuring C-reactive protein using crown ether--phosphate ester ionophores

A new electrochemical method for measurement of C-reactive protein (CRP) is presented. We have synthesized new crown ether-phosphate ester ionophores having high affinity for CRP. A study using proton nuclear magnetic resonance shows CRP binding to the ionophores in stoichiometric amounts. The incorporation of these crown ether-phosphate ester ionophores into poly(vinyl chloride) membrane electrodes yields a CRP-sensitive electrode with sensitivity in the microgram per milliliter range. The ionophore synthesis and preliminary electrode characteristics are described.     

Importance of multiple-phonon interactions in molecular dissociation and nanofabrication using optical near fields

A quasi-particle (exciton-phonon polariton) model, as a simple model of an optical near-field probe, is proposed to investigate an unresolved problem in photochemical processes, i.e., why a vapor molecule can be dissociated by an incident photon with less energy than the dissociation energy only if, not a propagating far field, but an optical near field is used, and what is the mechanism leading to the photon flux dependence of the deposition rates. Incident photon energy and intensity dependences of Zn deposition rates are analyzed, and good agreement between the theoretical and experimental results is obtained. It suggests that the probe system plays an important role in vibrational transitions as well as electronic transitions in photodissociation processes, and that the couplings between the optical near field and molecular vibrations are enhanced to permit a nonresonant photodissociation inherent in the optical near field.     

Improved nanofabrication through guided transient liquefaction

A challenge in nanofabrication is to overcome the limitations of various fabrication methods, including defects, line-edge roughness and the minimum size for the feature linewidth. Here we demonstrate a new approach that can remove fabrication defects and improve nanostructures post-fabrication. This method, which we call self-perfection by liquefaction, can significantly reduce the line-edge roughness and, by using a flat plate to guide the process, increase the sidewall slope, flatten the top surface and narrow the width while increasing the height. The technique involves selectively melting nanostructures for a short period of time (hundreds of nanoseconds) while applying a set of boundary conditions to guide the flow of the molten material into the desired geometry before solidification. Using this method we reduced the 3sigma line-edge roughness of 70-nm-wide chromium grating lines from 8.4 nm to less than 1.5 nm, which is well below the 'red-zone limit' of 3 nm discussed in the International Technology Roadmap for Semiconductors. We also reduced the width of a silicon line from 285 nm to 175 nm, while increasing its height from 50 nm to 90 nm. Self-perfection by liquefaction can also be extended to other metals and semiconductors, dielectrics and large-area wafers.     

Transition of MEMS technology to nanofabrication

The transition of MEMS technology to nano fabrication is a solution to the growing demand for smaller and high-density feature sizes in the nanometer scale. Nanoimprint lithography (NIL) techniques for fabricating micro- and nano-features are discussed including hot embossing lithography (HEL), UV Molding (UVM) and micro contact printing (microCP). Recent results in micro and nano-pattern transfer are presented where features ranged from < 100 nm to several centimeters. We also present a comparative study between standard glass microfluidic chips and their HEL counterparts by metrology. Hot-embossed microfluidic chips are shown to be faithful replicates of their parent stamps. NIL is presented as a promising avenue for low-cost, high throughput micro and nano-device fabrication.     

Pattern recognition using binary masks based on the fractional Fourier transform

This paper presents two new methodologies for pattern recognition invariant to position and rotation. The two methods use the correlation of signatures obtained using a binary rings mask created from the fractional Fourier transform (FRFT). An analysis of fragmented information was performed with 21 images of fossil diatom species. The methodologies were applied to 30 species of phytoplankton to test the performance when rotation distortion is present in a target. Also, a noise analysis was performed. Higher signature correlation values are achieved by working outside the Fourier plane by changing the order of the FRFT.     

纳米制造和测量技术产业化的研究

从加工尺度的连续性和加工技术的完整性这一新的角度,分析了纳米加工产业化面临的问题,并提出了相应的解决方案一多离子柬聚焦投影技术。多离子柬聚焦投影技术将填补传统微机加工技术和半导体图形技术之间0．5～5μm的加工空白,并会在1～100nm尺度间实现自上至下技术和自下至上技术的有机结合。纳米测量技术产业化的研究中,以提高扫描探针技术的样品质量作为出发点。在聚焦离子束和扫描电镜平台上集成Ar离子束的“三束”显微镜能有效降低样品的损伤,大大推动了纳米测量技术的发展。     

Achromatic quarter-wave plate using crystalline quartz

Achromatic wave plates are ideal components for use with tunable and multiline laser systems, broadband sources, and in astronomical instrumentation. The present study deals with the design and characteristics of two different quarter-wave achromatic retarders in the 500-700 nm range, using a cascaded system of two birefringent plates. The first of these shows a variation of less than ±0.5°, whereas the second system shows a variation of ±4° where the azimuth remains constant. Finally, a comparison between the two systems is made. The succinct and simple Jones matrix formalism has been used to derive the general expression for the equivalent retardation and azimuth of the combinations. It appears that the proposed arrangement has the promise of producing good achromatic combinations.     

Statistical optimization of the electrospinning process for chitosan/polylactide nanofabrication using response surface methodology

In this study, chitosan/polylactide (CP) blend solutions in trifluoroacetic acid as a co-solvent with different blend ratio were electrospun. Effects of different CP ratio and process parameters on the diameter of electrospun nanofibers were experimentally investigated. The fiber morphology and the distribution of fiber diameter were investigated by scanning electron microscopy. Response surface methodology (RSM) was used to define and evaluate a quantitative relationship between electrospinning parameters, average fiber diameters and its distribution for each chitosan–polylactide ratio. Applied voltage and polymer solution extrusion rate are the process variables which control the fiber diameter at similar spinning distances (15 cm). Fiber diameter was correlated to these variables by using a second-order polynomial function. The fibers were of diameter ranging from 94 to 389 nm. The predicted fiber diameters were in good agreement with the experimental results. Contour plots were obtained to identify the processing variables suitable for producing nanofibers. It was concluded that ratio of polylactide and chitosan in the blend polymer played an important role to the diameter of fibers and standard deviation of fiber diameter. The processing factors were found statistically significant in the production of nanofibers.     

Single digit nanofabrication by step-and-repeat nanoimprint lithography

A novel strategy for fabricating nanoimprint templates with sub-10 nm patterns is demonstrated by combining electron beam lithography and atomic layer deposition. Nanostructures are replicated by step-and-repeat nanoimprint lithography and successfully transferred into functional material with high fidelity. The process extends the capacity of step-and-repeat nanoimprint lithography as a single digit nanofabrication method. Using the ALD process for feature shrinkage, we identify a size dependent deposition rate.     

Fabrication of phase masks with variable diffraction efficiency using HEBS glass technology

A new fabrication method of apodized diffractive optical elements is proposed. It relies on using high energy beam sensitive glass as a halftone mask for variable diffraction efficiency phase masks generation in a resist layer. The presented technology is especially effective in mass production. Although fabrication of an amplitude mask is required, it is then repeatedly used in a single shot projection photolithography, which is much simpler and less laborious than the direct variable-dose pattern writing. Three prototypes of apodized phase masks were manufactured and characterized. The main advantages as well as limitations of the proposed technology are discussed.