Myoung Jin Park

Fabrication of a high-throughput near-field optical probe using a double metal layer

Metal-coated oxide nano-aperture arrays have been fabricated using a micro-fabrication technique including a stress-dependent oxidation, an isotropic wet etching of silicon oxide, and the metal deposition. Au, Al, and Al/Ti double metal layers have been deposited on nano-size oxide aperture arrays in order to provide a better uniformity of the coated metal film and an ideal aperture shape. The introduction of the Ti buffer layer reduced surface roughness during the reflow process of Al deposition and resulted in an ideal circular type aperture shape.

Fabrication of pyramidal probes with various periodic patterns and a single nanopore

The nanometer-scale patterned pyramidal probe with an electron beam-induced nanopore on the pyramid apex is an excellent candidate for an optical biosensor. The nanoapertures surrounded with various periodic groove patterns on the pyramid sides were fabricated using a focused ion beam technique, where the optical characteristics of the fabricated apertures with rectangular, circular, and elliptical groove patterns were investigated. The elliptical groove patterns on the pyramid were designed to maintain an identical distance between the grooves and the apex for the surface waves and, among the three patterns, the authors observed the highest optical transmission from the elliptically patterned pyramidal probe. A 103-fold increase of the transmitted optical intensity was observed after patterning with elliptical grooves, even without an aperture on the pyramid apex. The nanopore on the apex of the pyramid was fabricated using electron beam irradiation and was optically characterized.

Concentration-dependent redistribution of arsenic in silicon during thermal oxidation

Abstract The redistribution phenomena (such as pile-up, push-back) of arsenic impurities in silicon during thermal oxidation are dependent upon the oxidation rate, the diffusivities of arsenic in silicon and SiO2, and the segregation rate of arsenic impurities at the interface between the oxide and silicon. The diffusivity of arsenic in SiO2 is known to be negligible compared with the diffusivity of arsenic in silicon and the oxidation rate of silicon. The diffusivity of arsenic in silicon is also dependent on the arsenic concentration. The pile-up at the Si-SiO2 interface as a result of the concentration dependence of arsenic, has not reported so far. For silicon samples implanted with low fluences (1 × 1015 or 3 × 1015cm−2) of arsenic at 100 keV, a pile-up of arsenic was observed during thermal oxidation at 1050 °C, using Rutherford backscattering spectroscopy. For silicon samples implanted with fluences greater than 3 × 1016cm−2, push-back phenomena were observed. These phenomena can be explained only by the diffusivity of arsenic, dependent upon the concentration of arsenic in the silicon.

Fabrication of photonic force devices for biomolecule dynamics

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.

Design and fabrication of focusing nearfield optical probe for biomolecule trapping application

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.

Influence of arsenic in silicon on thermal oxidation rate

Abstract We have studied As clustering and oxidation of As-implanted Si after a preoxidation (ramp-up) period with (N2 + 1% O2) ambients. Sheet resistance measuremenrs along with channeling studies indicate that significant arsenic clustering and arsenic supersaturation in Si occurred after ramping periods at 750 °C and 850 °C compared with results at 950 °C and 1050 °C. For very high As implantation fluences, the arsenic supersaturation with cluster formation near the silicon surface produced a higher oxidation rate at 750 °C and 850 °C than at 950 °C.

Towards the plasmonic nanopore for single molecule analysis

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.

Fabrication of plasmonic nanopore by using electron beam irradiation for optical bio-sensor

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.

Au particle formation on the electron beam induced membrane

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.

Nanopore integrated with Au clusters formed under electron beam irradiation for single molecule analysis

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.