We fabricated the various nano-aperture plasmonic platforms on pyramid and on the flat membranes. The nano-apertures such as circular nanopore and nanoslit pores were fabricated. Optical characteristics were found to be dependent upon the aperture size and the sample thickness. The enhanced optical emission spectra with decreased aperture sizes have been observed due to spp-mediated emission at ~ 500 nm. In addition, the broad emission spectra in the visible and infrared region from the nanoslit array are obtained. The fabricated Au nano-aperture platform with a few nano-meter openings can be utilized as a single-molecule sensor.
The hour-glass type nanostructures are fabricated by using the conventional Si processes. When beaming though these structures, we observed that light is collected by the micro scale pyramidal cavity, funneled through the nano-aperture by plasmonic resonance and collimated with enhanced transmission by the surrounding horn-like mirrors (optical horn-effect). Optical transmissions through pyramidal probes with various nano-aperture diameters were measured to be dependent upon the aperture area. For a diameter less than ~ 50 nm or less than area with ~10,000 nm2, the transmitted optical intensities are increasing due to the spp-mediated intra-band emission. For the aperture diameter greater than 100 nm, the strong spp-coupled emission is shown. In addition, for the Au (7×7) slit aperture array platform with the slit aperture for a ~ 10 nm width, the broad emission spectra ranging from 600 nm to 860 nm are observed possibly due to nearfield coupling with localized surface plasmon polariton (LSPP).
Recently there have been significant interests about fabrication of optical nanopore for single molecule analysis and manipulation. However, due to very small amount of the optical intensity through the tiny size of the nano-aperture, optical intensity enhancement via plasmonic effect by using pore array or periodic groove patterns have been tried. In addition, the double slits with nanoscale width is reported to provide the constructive interference of the surface plasmonic wave. In this report, the nanoscale double slits with Au aperture array has been fabricated and optically characterized.
About sixty years ago, the biological cell counter with an electrical currents detection technique through a micrometer size orifice was invented by Dr. Coulter. A couple of years ago, the ultrafast portable pore device (MinION) with an electrical detection technique was manufactured by Oxford Nanopore Technology. However, high error rates over 80% from this solid state nanopore device is initially reported in several journals. The high error rates may have been contributed from the electrical double layer formed in the pore channel. Even though the error rates have been reduced significantly. Considering the fact that most biosensors are utilizing the optical detection technique, the optical pore device can be an excellent candidate for the next generation single molecule sensor. We will report the fabrication process of the plasmonic optical nanopores.
The Au nano-hole surrounded by the periodic nano-patterns would provide the enhanced optical intensity. Hence, the nano-hole surrounded with periodic groove patterns can be utilized as single molecule nanobio optical sensor device. In this report, the nano-hole on the electron beam induced membrane surrounded by periodic groove patterns were fabricated by focused ion beam technique (FIB), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Initially, the Au films with three different thickness of 40 nm, 60 nm, and 200 nm were deposited on the SiN film by using an electron beam sputter-deposition technique, followed by removal of the supporting SiN film. The nanopore was formed on the electron beam induced membrane under the FESEM electron beam irradiation. Nanopore formation inside the Au aperture was controlled down to a few nanometer, by electron beam irradiations. The optical intensities from the biomolecules on the surfaces including Au coated pyramid with periodic groove patterns were investigated via surface enhanced Raman spectroscopy (SERS). The fabricated nanopore surrounded by periodic patterns can be utilized as a next generation single molecule bio optical sensor.
Recently the single molecules such as protein and deoxyribonucleic acid (DNA) have been successfully characterized by using a portable solidstate nanopore (MinION) with an electrical detection technique. However, there have been several reports about the high error rates of the fabricated nanopore device, possibly due to an electrical double layer formed inside the pore channel. The current DNA sequencing technology utilized is based on the optical detection method. In order to utilize the current optical detection technique, we will present the formation of the Au nano-pore with Au particle under the various electron beam irradiations. In order to provide the diffusion of Au atoms, a 2 keV electron beam irradiation has been performed During electron beam irradiations by using field emission scanning electron microscopy (FESEM), Au and C atoms would diffuse together and form the binary mixture membrane. Initially, the Au atoms diffused in the membrane are smaller than 1 nm, below the detection limit of the transmission electron microscopy (TEM), so that we are unable to observe the Au atoms in the formed membrane. However, after several months later, the Au atoms became larger and larger with expense of the smaller particles: Ostwald ripening. Furthermore, we also observe the Au crystalline lattice structure on the binary Au-C membrane. The formed Au crystalline lattice structures were constantly changing during electron beam imaging process due to Spinodal decomposition; the unstable thermodynamic system of Au-C binary membrane. The fabricated Au nanopore with an Au nanoparticle can be utilized as a single molecule nanobio sensor.
Recently the single molecules such as protein and deoxyribonucleic acid (DNA) have been successfully characterized using a solidstate nanopore with an electrical detection technique. However, the optical plasmonic nanopore has yet to be fabricated. The optical detection technique can be better utilized as next generation ultrafast geneome sequencing devices due to the possible utilization of the current optical technique for genome sequencing. In this report, we have investigated the Au nanopore formation under the electron beam irradiation on an Au aperture. The circular-type nanoopening with ~ 5 nm diameter on the diffused membrane is fabricated by using 2 keV electron beam irradiation by using field emission scanning electron microscopy (FESEM). We found the Au cluster on the periphery of the drilled aperture under a 2 keV electron beam irradiation. Immediately right after electron beam irradiation, no Au cluster and no Au crystal lattice structure on the diffused plane are observed. However, after the sample was kept for ~ 6 months under a room environment, the Au clusters are found on the diffused membrane and the Au crystal lattice structures on the diffused membrane are also found using high resolution transmission electron microscopy. These phenomena can be attributed to Ostwald ripening. In addition, the Au nano-hole on the 40 nm thick Au membrane was also drilled by using 200 keV scanning transmission electron microscopy.
KEYWORDS: Gold, Electron beams, Transmission electron microscopy, Carbon, Particles, Chemical species, Contamination, Fabrication, Scanning electron microscopy, Statistical analysis
There have been tremendous interests about the fabrication of the Au plasmonic nanopore due to its capability of the nanosize optical biosensor. We have investigated the influence of low energy electron beam irradiation on an Au nanomembrane during Au nanopore formation. In this report, the influence of electron beam irradiation on the Au nanopore formation will be reported. The nanopores on the 200 nm thick Au membrane were initially fabricated using focused ion beam (FIB) and high energy electron beam techniques such as transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). During high energy electron beam by using TEM, either a "shrinking" or a "opening" phenomenon is reported dependent on the ratio of thickness to aperture diameter. However, for a FESEM electron beam irradiation, a shrinking phenomenon is always observed. In this report, the nanopore formation during FESEM electron beam irradiation will be reported depending upon energy absorption and thermal diffusivity.
KEYWORDS: Electron beams, Gold, Transmission electron microscopy, Absorption, Biosensors, Scanning electron microscopy, Silica, Molecules, Plasmonics, Ion beams
There have been tremendous interests about the fabrication of the Au plasmonic nanopore due to its capability of the nanosize optical biosensor. We have investigated the influence of low energy electron beam irradiation on an Au nanomembrane during Au nanopore formation. In this report, the influence of electron beam irradiation on the Au nanopore formation will be reported. The nanopores on the 200 nm thick Au membrane were initially fabricated using focused ion beam (FIB) and high energy electron beam techniques such as transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). During high energy electron beam by using TEM, either a “shrinking” or a “opening” phenomenon is reported dependent on the ratio of thickness to aperture diameter. However, for a FESEM electron beam irradiation, a shrinking phenomenon is always observed. In this report, the nanopore formation during FESEM electron beam irradiation will be reported depending upon energy absorption and thermal diffusivity.
KEYWORDS: Electron beams, Gold, Transmission electron microscopy, Silicon, Chemical species, Scanning electron microscopy, Nanolithography, Liquids, Microfabrication, Metals
Recently there have been tremendous interests about the fabrication of the solid state nanopore due to its capability of the nanosize biosensor. In this report, the dynamics of the Au nanopore formation on the pyramidal membrane will be reported. The nanopores on the microfabricated Au coated SiO2 pyramid were fabricated using focused ion beam (FIB) and high energy electron beam techniques such as transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). For high scanning electron beam irradiation using FESEM, shrinking of the Au nanopore was always observed. The nanopore formation dependent upon the primary electron voltage, and the scan rate of the FESEM electron beam was carefully examined. The higher closing rates for the faster scan rate and the lower electron accelerating voltage are observed. For the TEM electron beam exposure, the closing or the opening of the pore was observed depending upon the electron beam current. We do believe that this phenomenon can be attributed to the capillary force and the vaporization of the materials on the viscous liquid membrane due to TEM electron beam irradiation.
The Al Nano apertures surrounded by periodic patterns on the pyramidal structures were fabricated. The nanometric size aperture with ~ 100 nm diameter surrounded by equidistant elliptic groove patterns presented greater transmission than the aperture with circular groove patterns. The translocation of λ-DNA through these fabricated nanostructures was tested using electrically biased techniques. We observed the strong fluorescent optical signal from the translocated DNA through the nanoprobe with a charge coupled device camera. The optical force driven DNA translocation though a nanoprobe surrounded with elliptically patterned grooves is under investigation.
Recently there has been tremendous interest about the dynamical sequence of fabrication of the solid state nanopore due to its capability of the nanosize solid state biosensor as a single molecule sensor. Depending upon the instruments such as transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM), the dynamics of nanopore formation present different physical mechanisms. In this report, formation of the nanopores was examined. Metallic nanopores with ~ 50 nm diameter on top of the oxide pyramid were fabricated using conventional Si microfabrication techniques followed by wet isotropic etching of the oxide; sputter metal deposition followed by the focused ion beam (FIB) techniques. No shrinking phenomena were observed for the nanopore diameter greater than 50 nm under electron beam irradiation using TEM. However, for high scanning electron beam irradiation using FESEM, shrinking of the Au nanopore was always observed. We do believe that these phenomena can be attributed to the liquid phase surface modification for TEM electron beam and adiabatic solid state phase surface modification for high scanning FESEM. For a huge amount of energy input from high scan rate and the poor thermal conduction to its surrounding area, the energy spike inside the electron penetration area would occur. However, a TEM electron beam irradiation without repetitive scan can provide the liquid phase surface modification.
Recently there have been tremendous interests about the fabrication of the solid state nanopore due to the capability of
the solid state nanopore as a single molecule sensor. The SiN nanopore and the SiO2 nanopore have been fabricated with
high energy electron beam exposure such as transmission electron microscopy, field emission electron microscopy, and
focused ion beam sculpting. However, the plasmonic Au nano-pore can be utilized as a nanobio optical sensor due to the
106 fold increase of the Raman signal intensity. Hence, in this report, the fabrication of the plasmonic nanopore with less
than ~ 10 nm on the apex of the micronsize pyramidal structure using various high energy electron beam exposure.
Under the electron beam exposure of FESEM followed by EPMA, the widening and the shrinking of the Au nanopore
were observed depending upon the EPMA probe current. The diameters of the Au nanopore was also reduced
successively from ~ 5 nm down to zero using 200 keV TEM. From these experimental results, the dynamics of the
nanopore formation are found to depend on the viscosity of the membrane, radiation damage, and evaporation of the
materials under high vacuum condition. This fabricated plasmonic nano-pore device can be utilized as geneome
sequencing device or a single-molecule sensor.
Recently there have been tremendous interests about the single molecule translocation through the SiN nanopore array.
For DNA translocation and characterization, SiN nanopore array is easy to fabricate with high energy electron beam
exposure. It is well known that the metallic nanopore can provide the huge enhancement, 106 fold increase of the
electromagnetic field at the metallic nanopore due to "hot spot" effect. In addition, the fabricated plasmonic micro device
provides huge photon transmission through the fabricated nanochannel. In this report, we microfabricated the plasmonic
nanopore with ~ 101 nm on top of the micronsize pyramidal structure for translocation and optical characterization using
conventional microfabrication process and electron beam heating. The reduced Au nanopore due to electron beam
heating is found to provide the huge optical transmission resulted in the huge photonic pressure gradient between the free
space and nanopore inside. The huge pressure gradient can be attributed to the resonance transmission between the
fabricated V groove cavity and the nanosize waveguide formed during the metal deposition. This fabricated plasmonic
nano-aperture device can be utilized as bio-molecule translocation and optical characterization.
We microfabricated the plasmonic nanopore with ~ 1 nm on top of the pyramid for single molecule dynamics. This
plasmonic micro device provides huge photon transmission through the fabricated nanochannel on the top of the
pyramidal structure. This can generate the huge photonic pressure gradient between the free space and nanopore inside.
The huge pressure gradient can be attributed to the resonance transmission between the fabricated V groove cavity and
the nanosize waveguide formed during the metal deposition. This fabricated huge photonic device can be utilized as biomolecule
translocation and single molecule dynamics.
e macro size pyramidal horn probe such as klystron horn antenna has been used to provide the excellent focusing
capabilities in microwave region. In the similar way, the pyramidal probe with the micron size mirror (pyramidal horn
probe) has been fabricated with a nano-size aperture with diameter ranging from 30 to 330 nm on its apex. Light
transmission through the micro-fabricated pyramidal horn probe has been measured to enhance the light transmission
due to resonant effects between the cavity mode and the slit modes in the probe, along with directionality of the
transmitted beam. The resonant tunneling between two standing waves in the input groove and in the output groove can
provide the transmission enhancements. Below ~170 nm, the output power normalized to the input power (ratio) has
been increased with decreasing diameter. On the other hand, for the diameter ranging from 330 to 170 nm, the ratio has
been decreased with decreasing diameter. The transmission (T) is measured to be inversely proportional to the area (A),
and TA value for input wavelength 532 nm is found to be constant, 0.136 for the diameter below 160 nm, and to be
0.053 for diameter greater than 160 nm.
We show that accumulation of charges at the metal edges via light-induced currents creates large horizontal electric
field, which in effect attracts the incoming light. The enhanced field is fully propagating towards the far-field because no
cut-off exists. With the amplitude enhancement in the range of 1,000, the intensity enhancement of 106, and the
nonlinear enhancement of 1012, this structure can be an excellent launching pad for inducing broad-band nonlinearity,
small signal detection in astronomy or biology, and for surface enhanced Raman scattering.
There has been a tremendous interest about the trapping of a single biomolecule using nearfield optical trapping. The optical trapping of a biomolecule can be accomplished by controlling both scattering force on the molecule and field gradient force. In order to achieve nearfield optical trapping of the biomolecule, it seems that the radiant trapping force should be greater than the Brownian motion of the molecule in the liquid and the gravity. The radiation force is proportional to the nearfield intensity of the aperture. Though, the throughput of the conventional fiber probe is known to have weak light intensity due to the long, narrow waveguide. In order to better confine the molecule around the aperture, the greater throughput of the light intensity through the aperture is desirable due to wider tapered angle of waveguide. In this report, the nanosize circular metal shape around the subwavelength-size oxide aperture was designed and fabricated using physical metallic deposition of Au or bimetallic Al and Ti. The circular metallic shape (metallic nanoflower) around the subwavelength-size metallic aperture is supposed to focus the horizontal evanescent electromagnetic field toward the propagating direction. This can provide an enhanced evanescent field and an increased gradient force toward the axis of propagating direction. Therefore the nanoflower around the nano-aperture would be expected to better confine a bio-molecule in a nanoscale region.
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