Electron Beam Nanolithography Research Articles

Plasmonic-Metal Nanostructures-Enhanced Photoconductive Terahertz Emission and Detection

Photoconductive antennas based on low-temperature gallium arsenide (LT-GaAs) with a gold plasmonic-gold grating made of nanorods and nanoislands have been developed and fabricated. The antennas were produced using molecular beam epitaxy and electron-beam nanolithography. LT-GaAs samples with a high annealing temperature of 943 K were employed in the fabrication process. It has been demonstrated that plasmonic nanostructures significantly enhance the efficiency of light-to-terahertz radiation conversion by photoconductive antennas.

Review of: "Electron beam nanolithography provides the possibility of precise control of nanostructure features that form the basis of various device technologies"

Review of: "Electron beam nanolithography provides the possibility of precise control of nanostructure features that form the basis of various device technologies"

Review of: "The electron beam nano-lithography process is inherently slow compared to other methods because the electron beam requires a limited time at each point of exposure"

Review of: "The electron beam nano-lithography process is inherently slow compared to other methods because the electron beam requires a limited time at each point of exposure"

Continuously tunable middle-IR bandpass filters based on gradient metal-hole arrays for multispectral sensing and thermography

Continuously tunable middle-infrared bandpass filters have been developed based on gradient metal-hole arrays with two distinct geometries. The rotation filter relies on an array of metal holes with gradually changing periods and hole sizes in the azimuthal direction, while the translation filter exploits a metal-hole array with a linear gradient. The filters are fabricated in a Ti film on a ZnSe substrate using electron-beam nanolithography. They are characterized experimentally using Fourier-transform infrared spectroscopy, and the observed results are compared with numerical predictions of the finite element method. The developed filters offer wide spectral tunability when operating with a focused beam. Particularly, the central wavelength of the transmission band is tunable in the [Formula: see text] range, for the rotation filter, and in the [Formula: see text] range for the translation one, as a linear function of the filter angular or linear displacement. The filters feature relatively broad bandwidths of [Formula: see text], while their spectral contrast and energy efficiency depend on the gradient type. The filter spectral response function shape and the extent of its spectra tunability can be further optimized by judicious design of the hole geometry and the metal-hole array gradient, respectively. The developed filters hold strong potential in the infrared multispectral sensing and imaging, thanks to their conceptual simplicity. Considering the linearity of Maxwell’s equations and availability of appropriate technologies for the fabrication of gradient arrays of sub-wavelength metal holes, the developed concept can be translated to other spectral ranges.

Observation of enhanced terahertz emission in two-dimensional metal line arrays on GaAs surfaces

Enhanced terahertz (THz) emission was observed from semi-insulating GaAs with square and diamond two-dimensional metal line arrays (2DMLA’s) of subwavelength periodicity. An externally-applied magnetic field was used to generate elliptically-polarized THz radiation from the samples and the THz emission characteristics were measured using a THz time-domain spectroscopy setup in transmission geometry. Finite difference time-domain simulations verified the enhancement as due to confinement of the THz electric field at the 2DMLA apertures. These results demonstrating spoof plasmonic enhancement effects may be useful for future photoconductive antenna emitter designs incorporating 2D micro-scale integrated optics, THz metamaterials, without the need for expensive electron beam nanolithography.

An Acousto-Electric Nanobiosensor

A technology is developed that uses two multiscale structures on a single crystal piezoelectric substrate of lithium niobate. A system of counter-pin electrodes for an acoustic delay line operating in the 2–3 MHz range is formed via photolithography. The system is combined with nanotransducers 60–80 nm in size, produced by means of negative electron-beam nanolithography.

Triindolyl Macrocycle as a Molecular Platform in the Synthesis of Sumanene-Containing Polyphenols

A new strategy has been suggested for the synthesis of sumanene-containing polyphenols chemically bound to a molecular platform based on the triindolyl macrocycle. The initial assembly has been obtained by the Suzuki–Miyaura reaction of a bromo-containing indolyl macrocycle and boryl derivative of N,N'-disumanenylaniline. Subsequent benzylation with 3,5-dimethoxybenzyl bromide, exhaustive demethylation of the modified macrocycle, and partial blocking of the corresponding phenolic hydroxyls by two different acid-labile protective groups have led to the formation of the target polyphenol containing sumanene fragments. The obtained polyphenol has allowed us to develop on its basis a new positive resist for electronbeam nanolithography. This resist can realize topological structures with resolution of 9–12 nm.

Porphyrin Derivatives of Macrocyclic Tetraindoles: Synthesis and Chemical Transformations

Polyphenols chemically bonded to a molecular platform based on macrocyclic tetraindole porphyrin derivatives were synthesized for the first time. The tetraindole was prepared by two-step tetramerization of 3-(4′-bromophenyl)-4,6-dimetoxyindole. Polyphenols of this type were obtained by the Suzuki–Miyaura reaction between bromo-containing cyclic tetraindole and monoboryl-substituted porphyrin. The subsequent transformations of this molecular construction gave rise to epoxidized polyphenol on a tetraindole support, which served for the development of a new negative resist for electron-beam nanolithography. The resist can form patterns with a 12 nm resolution.

Adsorption on Nanopores of Different Cross Sections Made by Electron Beam Nanolithography.

Adsorption on nanoporous matrices is characterized by a pronounced hysteresis loop in the adsorption isotherm, when the substrate is loaded and unloaded with adsorbate, the origin of which is a matter of immense debate in the literature. In this work, we report a study of argon adsorption at 85 K on nonconnecting nanopores with one end closed to the surrounding where the effects of different pore cross sections fabricated by electron beam lithography (EBL) are investigated. A polymethylmethacrylate (PMMA) resist is deposited on the electrodes of a sensitive quartz crystal microbalance without degradation of the resonance quality factor or the long-term and short-term stabilities of the device even at cryogenic temperatures. Four different pores' cross sections: circular, square, rectangular, and triangular, are produced from EBL, and the isotherms for these pore shapes exhibit pronounced hysteresis loops whose adsorption and desorption branches are nearly vertical and have almost the same slopes. No difference is observed in the hysteresis loops of the isotherms for the pores with triangular and square cross sections, whereas the hysteresis loop for the pore with circular cross sections is much narrower, suggesting that they are more regular than the other pores. All of these observations suggest that the hysteresis behavior resulted mainly from microscopic geometric irregularities present in these porous matrices.

GaN Membrane Supported SAW Pressure Sensors With Embedded Temperature Sensing Capability

This paper presents the fabrication and characterization of a GHz operating surface acoustic wave (SAW)-based pressure sensor on a 1.2- $\mu \text{m}$ -thin GaN membrane. Two types of interdigitated transducers are manufactured using electron beam nanolithography to obtain finger and interdigit spacing widths, one with 170 nm and the other 200-nm-half pitch. Micromachining techniques are used to obtain the 1.2- $\mu \text{m}$ -thin membrane. The resonance frequency shift of the SAW, the pressure sensitivity, $s_{p}$ , as well as the pressure coefficient of frequency (PCF), were experimentally determined and analyzed, both for the Rayleigh as well as for the symmetrical Lamb propagation mode, in the 1 to 7 Bar pressure range. Record values for $s_{p}$ (up to 6 MHz/Bar) and PCF (up to 537 ppm/Bar) have been obtained, especially for the symmetrical Lamb propagation mode also due to the very high frequency operation (5–11.5 GHz). The effect of different orientations of the SAW device (in the $\textrm {[1}\bar {\textrm {1}} \textrm {00]}$ and $\textrm {[11}\bar {\textrm {2}} \textrm {0]}$ directions) on the frequency response and sensitivity is also analyzed. The possibility to determine simultaneously the pressure and the temperature with the same SAW structure operating as a dual sensor has been demonstrated.

Symmetrical triindole as a central unit in the fluorene-containing polyphenol assembly

A new strategy was proposed for the synthesis of fluorene-containing indole polyphenols, based on the Suzuki–Miyaura reaction of hexabrominated symmetric indole trimer with the monoboryl N,N'-di[9,9'-bis(3',5'-dimethoxybenzyl)fluoren-2'-yl]aniline derivative and subsequent chemical transformations. The prepared compound was applicable for the development of a promising positive resist for electron-beam nanolithography capable of forming patterns with a 12 nm resolution.

Plasmonic Properties of Nanostructured Diamond Like Carbon/Silver Nanocomposite Films with Nanohole Arrays

Plasmonic properties of the diamond like carbon nanocomposite films with embedded silver nanoparticles with patterned nanohole arrays were analyzed in this study. The films were deposited by unbalanced reactive magnetron sputtering of silver target. Nanopatterning of the films was performed by combining electron beam nanolithography and ion beam etching techniques. Modeling of plasmonic properties was done using the classical Maxwell-Garnett theory. Modeling data and experimental results were in good accordance. Formation of the nanohole pattern in diamond like carbon films doped with silver resulted in decreased intensity of the surface plasmon resonance absorbance peak. No new absorbance or transmittance peaks were observed after the nanopattering. It was explained by extraordinary transmission effect in nanostructured DLC : Ag film films due to plasmon polariton resonance inside of the nanoholes. DOI: http://dx.doi.org/10.5755/j01.ms.22.4.13193

Fabrication and Characterization of a Single Electron Transistor Based on a Silicon-on-Insulator**Supported by the National Natural Science Foundation of China under Grant Nos 11074280 and 11403084, the Instrument Developing Project of Chinese Academy of Sciences under Grant No YZ201152, the Fundamental Research Funds for Central Universities under Grant Nos JUSRP51323B and JUDCF12032, the Joint Innovation Project of Jiangsu Province under

A single electron transistor based on a silicon-on-insulator is successfully fabricated with electron-beam nanolithography, inductively coupled plasma etching, thermal oxidation and other techniques. The unique design of the pattern inversion is used, and the pattern is transferred to be negative in the electron-beam lithography step. The oxidation process is used to form the silicon oxide tunneling barriers, and to further reduce the effective size of the quantum dot. Combinations of these methods offer advantages of good size controllability and accuracy, high reproducibility, low cost, large-area contacts, allowing batch fabrication of single electron transistors and good integration with a radio-frequency tank circuit. The fabricated single electron transistor with a quantum dot about 50nm in diameter is demonstrated to operate at temperatures up to 70 K. The charging energy of the Coulomb island is about 12.5 meV.

Arrays Produced by Electron Beam Nanolithography from Fe3O4 Compressed Nanoparticles Targets

Arrays Produced by Electron Beam Nanolithography from Fe₃O₄ Compressed Nanoparticles Targets

Cross-linkable linear copolymer with double functionality: resist for electron beam nanolithography and molecular imprinting

The first demonstration of a molecularly imprinted polymer patterned by electron beam lithography (EBL) direct writing is reported. The polymeric mixture is based on a linear co-polymer that behaves simultaneously as a positive-tone EBL resist and, after polymerization in the presence of rhodamine 123 (R123) as a model analyte, as a selective and sensitive synthetic receptor for the template. Analyte binding was evaluated by fluorescence confocal microscopy and the imprinting effect was confirmed in the presence of compounds structurally related to R123.

Single C-Reactive Protein Molecule Detection on a Gold-Nanopatterned Chip Based on Total Internal Reflection Fluorescence

Single C-reactive protein (CRP) molecules, which are non-specific acute phase markers and products of the innate immune system, were quantitatively detected on a gold-nanopatterned biochip using evanescent fieldenhanced fluorescence imaging. The 4 × 5 gold-nanopatterned biochip (spot diameter of 500 nm) was fabricated by electron beam nanolithography. Unlabeled CRP molecules in human serum were identified with single-molecule sandwich immunoassay by detecting secondary fluorescence generated by total internal reflection fluorescence (TIRF) microscopy. With decreased standard CRP concentrations, relative fluorescence intensities reduced in the range of 33.3 zM-800 pM. To enhance fluorescence intensities in TIRF images, the distance between biochip surface and CRP molecules was optimally adjusted by considering the quenching effect of gold and the evanescent field intensity. As a result, TIRF only detected one single-CRP molecule on the biochip the first time.

Microfluidic integrated multi-walled carbon nanotube (MWCNT) sensor for electrochemical nucleic acid concentration measurement

A microfluidic assisted electrochemical (EC) biosensing platform based on vertically aligned multi-walled carbon nanotubes (MWCNTs) embedded in SiO2 was developed using multi-scale manufacturing techniques. The MWCNT-EC sensor was fabricated using electron beam (E-beam) nanolithography, thin-film metal deposition and reactive/electrochemical etching. The MWCNT-EC sensor was integrated with a microfluidic EC cartridge including the counter and reference electrodes and a PDMS microfluidic channel on a glass substrate. After packaging the MWCNT chip and microfluidic EC cartridge into a manifold which included sample inlet/outlet, electrical connectors and a miniaturized potentiostat, the platform was characterized with differential pulse voltammetry (DPV) using ferrocyanide and ruthenium(II) solutions. The DPV measurement results are consistent with commercial EC systems. Microfluidic nucleic acid hybridization was demonstrated using the MWCNT chip on which the MWCNT tips were functionalized with single stranded DNA (ssDNA) probes. The synthetic complementary ssDNA targets were input through the microfluidic channel and hybridized with the functionalized ssDNA probes. The relative DPV peak magnitude linearly correlated with the target DNA concentration. This platform provides a simple way to integrate a MWCNT biosensor with microfluidics as an electronic system for a variety of possible nucleic acid analyses.

Quenching effect on gold nano-patterned cardiac troponin I chip by total internal reflection fluorescence microscopy

Total internal reflection fluorescence microscopy (TIRFM) was investigated for enhanced detection sensitivity of cardiac troponin I (cTnI) on a gold nano-patterned protein chip. A 4×5 nanoarray patterning of a gold chip based on a single-molecule sandwich immunoassay was prepared with a spot diameter of 500nm on glass substrates formed via electron-beam nanolithography. Quantitative trace analysis was possible as a function of increasing total internal reflection fluorescence intensity in the range of 84aM–350pM at prism-type and 35aM–350pM at objective-type TIRFM. Although using same gold nano-patterned cTnI chips, however, the objective-type TIRFM showed enhanced detection sensitivities 2.4 times better than the prism-type due to weaker gold quenching. This result is also about 7000 times lower in the detection limit compared with those obtained by conventional commercial sandwich enzyme-linked immunosorbent assay techniques.

Wide-range quantification of human thyroid-stimulating hormone using gold-nanopatterned single-molecule sandwich immunoassay chip

We performed wide-range quantification of human thyroid-stimulating hormone (hTSH) using a gold nano-patterned sandwich immunoassay chip. Objective-type total internal reflection fluorescence microscopy (TIRFM) was used to detect hTSH at the single-molecule level. A gold spot with a diameter of 100nm on a 10-mm square glass substrate was fabricated by electron beam nanolithography. When hTSH bound to antibodies conjugated to each 100-nm gold spot, there was an increase in the relative fluorescent intensity (RFI). The detection limit of this “TSH-nanoarray chip” was 360zM (equivalent to five molecules), which demonstrated that a TSH-nanoarray chip could be used for detection at the single-molecule level. A linear response was observed over a wide dynamic range (from 360zM to 36pM, R=0.9812) without a fluorescence quenching effect. A significant enhancement in the sensitivity (∼12,000-fold) was achieved with the 100-nm gold nano-patterned chip compared with results obtained using a traditional chemiluminescence immunoassay for the evaluation of TSH in human serum.

Electron beam lithography on vertical side faces of micrometer-order Si block

Electron beam (EB) nanolithography on resist films coated on vertical side faces of Si blocks with micrometer-order size is demonstrated. This is achieved by combining the authors’ original three-dimensional (3D) EB writing technique with the authors’ newly developed low-viscosity resist solution. Resist coating with a 2-butanone/hexane low-viscosity solution enables the authors to uniformly coat a high-resolution EB resist [poly(methyl methacrylate)] on the vertical side faces of Si blocks. The mechanism of uniform coating on the vertical side faces can be understood by considering the lower viscosity of the authors’ resist solution. Moreover, Monte Carlo simulation and experimental 3D EB lithography reveal that dense nanopatterning on opposite side faces of a micrometer-order block with simultaneous development is as attainable as that on a flat substrate. The combination of the resist-coating method and 3D EB writing with ion etching from horizontal directions of substrates is promising for creating 3D nanostructures in semiconductors and thus for 3D nanotechnology.