Young Min Jhon - Academia.edu (original) (raw)

Papers by Young Min Jhon

arXiv (Cornell University), Jan 29, 2013

We report a molecular dynamics study on the tensile mechanics of graphene as gradually rotating t... more We report a molecular dynamics study on the tensile mechanics of graphene as gradually rotating the tensile direction from armchair to zigzag direction, covering the complete range of chiral directions which has never been explored so far. We observed monotonic increases of tensile strength and strain as the chiral (rotational) angle increases. Key feature is their negligible changes up to chiral angle of ~12° and the subsequent rapid increases and this pattern holds for all temperatures examined here (100-700 K). Considering a topologically consistent (zigzag-lines) breaking of graphene, we presented a unified fracture model that successfully reproduced the simulation results as well as explaining their physical origin. Notably, we found that the elastic stress of graphene is quasi-isotropic for all chiral directions in contrast to its anisotropic fracture behavior. Through the indentation simulations of graphene, we demonstrated that our rationale established in uniaxial (1D) tensile systems is applicable to 2D tensile systems as well.

Journal of the Optical Society of Korea, 2009

Journal of the Optical Society of Korea, 2008

The relative intensity noise (RIN) characteristics in 405 nm blue laser diodes grown on wurtzite ... more The relative intensity noise (RIN) characteristics in 405 nm blue laser diodes grown on wurtzite AlGaInN multiple quantum well structures were investigated using the rate equations with the quantum Langevin noise model. The device parameters were extracted from the optical gain properties of the MQW active region using the self-consistent numerical method developed for calculating the multiband Hamiltonian in the strained wurtzite crystal. These methods have been applied to laser diodes for various conditions including the external feedback and the high frequency current injection.

New Journal of Physics, 2017

We realize a nanomechanical impact oscillator driven by a radiofrequency signal. The mechanical i... more We realize a nanomechanical impact oscillator driven by a radiofrequency signal. The mechanical impact of the oscillator is demonstrated by increasing the amplitude of the external radiofrequency signals. Electron transport in the system is dramatically modified when the oscillator is strongly driven to undergo forced impacts with electrodes. We exploit this nonlinear kind of electron transport to observe the current response in the chaotic regime. Our model adopting the Sharvin conductance at the moment of impact provides a description of the rectified current via the impact oscillator in the linear regime, revealing a path towards chaos.

Scientific Reports, 2017

Surface plasmon polaritons have attracted broad attention in the optoelectronics field due to the... more Surface plasmon polaritons have attracted broad attention in the optoelectronics field due to their ability to merge nanoscale electronics with high-speed optical communication. As the complexity of optoelectronic devices increases to meet various needs, this integration has been hampered by the low coupling efficiency of light to plasmonic modes. Here we present a method to maximize the coupling of far-field optical waves to plasmonic waves for arbitrarily complex devices. The method consists of experimentally identifying the eigenchannels of a given nanostructure and shaping the wavefront of incident light to a particular eigenchannel that maximizes the generation of plasmonic waves. Our proposed approach increases the coupling efficiency almost four-fold with respect to the uncontrolled input. Our study will help to facilitate the integration of electronics and photonics.

Nature communications, Jan 6, 2017

Merging multiple microprocessors with high-speed optical networks has been considered a promising... more Merging multiple microprocessors with high-speed optical networks has been considered a promising strategy for the improvement of overall computation power. However, the loss of the optical communication bandwidth is inevitable when interfacing between optical and electronic components. Here we present an on-chip plasmonic switching device consisting of a two-dimensional (2D) disordered array of nanoholes on a thin metal film that can provide multiple-input and multiple-output channels for transferring information from a photonic to an electronic platform. In this device, the surface plasmon polaritons (SPPs) generated at individual nanoholes become uncorrelated on their way to the detection channel due to random multiple scattering. We exploit this decorrelation effect to use individual nanoholes as independent antennas, and demonstrated that more than 40 far-field incident channels can be delivered simultaneously to the SPP channels, an order of magnitude improvement over conventi...

Scientific reports, Jan 22, 2015

Terahertz (THz) electromagnetic wave has been widely used as a spectroscopic probe to detect the ... more Terahertz (THz) electromagnetic wave has been widely used as a spectroscopic probe to detect the collective vibrational mode in vast molecular systems and investigate dielectric properties of various materials. Recent technological advances in generating intense THz radiation and the emergence of THz plasmonics operating with nanoscale structures have opened up new pathways toward THz applications. Here, we present a new opportunity in engineering the state of matter at the atomic scale using THz wave and a metallic nanostructure. We show that a medium strength THz radiation of 22 kV/cm can induce ionization of ambient carbon atoms through interaction with a metallic nanostructure. The prepared structure, made of a nano slot antenna and a nano island located at the center, acts as a nanogap capacitor and enhances the local electric field by two orders of magnitudes thereby causing the ionization of ambient carbon atoms. Ionization and accumulation of carbon atoms are also observed t...

ACS Macro Letters, 2012

We report on establishing the polydispersity in chemical composition (PCC) and polydispersity in ... more We report on establishing the polydispersity in chemical composition (PCC) and polydispersity in monomer sequence distribution (PMSD) in random copolymers of poly(styrene-co-4-bromostyrene) (PBr x S), where x = (0.385 ± 0.035) is the mole fraction of the 4bromostyrene units (4-BrS), prepared by electrophilic substitution of bromine in the para-position of the phenyl ring of the parent polystyrene. Upon fixing the total number of repeating units, we tune the distribution of styrene and 4-BrS segments in PBr x S by carrying out the bromination reaction on polystyrene homopolymers in different solvents. While PBr x S with relatively random comonomer distribution is prepared in 1-chlorodecane, random-blocky sequences of 4-BrS in PBr x S are achieved by carrying out the bromination reaction in 1-chlorododecane. The PCC in both copolymers is established by fractionating both polymers using interaction chromatography (IC) and determining the chemical composition of the individual fractions by neutron activation analysis (NAA). The NAA data along with IC experiments reveal that the random-blocky sample possesses a narrowed PCC relative to a specimen with a more random comonomer sequence distribution. The full width at halfmaximum (fwhm) in the chemical composition profile from IC is used to quantify PCC; the random mother sample possessed a 25% fwhm, while the random blocky mother sample has a fwhm equal to 8.7%. The change in the adsorption enthalpy per brominated segment due to adsorption is determined to be ≈1.5 times greater for the random-blocky than the relatively random sample, proving that more pronounced cooperative adsorption occurs in the case of the random-blocky sample relative to the random copolymer sample. Computer simulation employing the discontinuous molecular dynamic scheme further reveals that the distribution of comonomer sequences, that is, PMSD, in the random-blocky copolymer is narrower than that in the copolymer with a random distribution of both monomers. R andom copolymers (RCPs) are long chain macromolecules composed of two or more chemically distinct units. Unlike copolymers with ordered sequence distributions, that is, alternating or block, the arrangement of the different monomers units inside RCPs does not possess a long-range order. In addition, due the stochastic nature of processes during the synthesis of RCP (vide infra), the RCPs are not chemically homogeneous and do not possess a unique comonomer sequence distribution. To make the matter even more complicated, just like in any synthetic polymeric systems, there may be a distribution of the lengths (i.e., molecular weights) for all polymers. The existence of the three types of heterogeneities, that is, (1) polydispersity in chemical composition (PCC), (2) polydispersity in monomer sequence distribution (PMSD), and (3) polydispersity in molecular weight (PMW), makes the complete characterization of RCPs very challenging because the mutual contributions of all polydispersities mentioned above are interconnected. In this Communication, we attempt to deconvolute, for the first time,

Hankook Kwanghak Hoeji, 2009

2009 Conference on Lasers & Electro Optics & The Pacific Rim Conference on Lasers and Electro-Optics, 2009

We proposed an all-optical logic system constructed by combining cross-waveguide geometries inclu... more We proposed an all-optical logic system constructed by combining cross-waveguide geometries including nonlinear cavity enabling all-kinds of logic gates. Proposed logic system is reconfigurable into any kinds of Boolean operations by appropriate placing of defect rods and adjusting its refractive index.

Polymer, 2012

We examined the onset of the cloud point in dilute aqueous solutions of gradient copolymers of 2h... more We examined the onset of the cloud point in dilute aqueous solutions of gradient copolymers of 2hydroxyethyl methacrylate and dimethylaminoethyl methacrylate. Dynamic Light Scattering (DLS) and transmittance measurements both indicate that the copolymer solution cloud point decreases with increasing copolymer gradient strength, defined as the largest difference in the instantaneous composition along the copolymer. While transmittance measurements suggest that macroscopic clouding does not set in until 30% of the polymer chain becomes insoluble, DLS experiments, which are more sensitive to the onset of aggregation, indicate that the onset of aggregation occurs at the point where the least soluble polymer chain end becomes insoluble. Collectively, our data indicate that the macroscopic cloud point transition is highly sensitive to co-monomer sequence distribution of the copolymers, with its onset and transition breadth tunable through copolymer gradient strength.

Optical and Quantum Electronics, 2008

Microelectronic Engineering, 2013

BeO was investigated as the interface passivation layer (IPL) between a high-k dielectric and a I... more BeO was investigated as the interface passivation layer (IPL) between a high-k dielectric and a III-V compound semiconductor substrate in metal-oxide-semiconductor (MOS) devices. One of the critical issues facing the fabrication of next generation MOS devices is the minimization of damage to the III-V semiconductor substrate during the etching of the thin IPL. In this study, atomic layer etching (ALET) was investigated for etching of BeO as the IPL on a GaAs substrate to control the etch depth precisely and to minimize the damage to the III-V semiconductor substrate. By using ALET to etch BeO, which uses BCl 3 as the adsorption gas for the formation of chloride compounds (Be-Cl and BCl-O) and Ar as the desorption gas for the removal of the chloride compounds, a self-limited, one-monolayer etch rate of about 0.75 Å/cycle was achieved with no increase of surface roughness and without change of surface composition. Moreover, under the BeO ALET conditions, which are able to precisely stop etching over the GaAs substrate after removing BeO, the exposed GaAs substrate showed surface composition and surface roughness similar to those of the as-received GaAs substrate.

Microelectronic Engineering, 2014

Macromolecules, 2008

We report on the kinetics of the bromination of free polystyrene (PS) chains in bulk solution and... more We report on the kinetics of the bromination of free polystyrene (PS) chains in bulk solution and those anchored on flat solid substrates by performing the bromination reaction in different solvents, including nitrobenzene (NB), 1-chlorodecane (CD), 1-chloroundecane (CUD), and 1-chlorododecane (CDD), at various temperatures. We find that bulk bromination of PS follows the second-order kinetic in bromine and the reaction rate increases with increasing dielectric constant of the solvent (ε). In spite of ε CDD > ε CD , the bulk bromination kinetics of PS in CDD is slower than that in CD because of lower solubility of PS in CDD than in CD. In addition, we demonstrate that the reaction rates for brominating PS brushes anchored to flat solid substrates are much slower than those for brominating free PS chains in bulk solution. We attribute this behavior to steric hindrance due to PS confinement on the substrate.

Macromolecular Rapid Communications, 2009

Interaction chromatography has been employed to validate that adsorption of poly[styreneco-(4-bro... more Interaction chromatography has been employed to validate that adsorption of poly[styreneco-(4-bromostyrene)] (PBr x S) random copolymers, where x denotes the mole fraction of 4bromostyrene (4-BrS) in PBr x S in solution depends on the average number of adsorptive segments, the type of adsorbing substrate, and on the co-monomer sequence distribution in PBr x S.