• Advances in nano research
• /
• v.16 no.3
• /
• pp.273-288
• /
• 2024

The geometrical nonlinear vibrations of the gold nanoscale rod are investigated for the first time by considering the internal modals interactions using different nonlinear beam theories. This phenomenon is usually one of the important features of nonlinear vibration systems. For a more detailed analysis, the von-Karman effects, preserving all the nonlinear terms in the strain-displacement relationships of gold nanoscale rods in three displacement directions, are considered to analyze the nonlinear axial vibrations of gold nanoscale rods. It uses highly accurate analytical-numerical solutions for the clamped-clamped and clamped-free boundary conditions of nanoscale gold rods. Also, with the help of Hamilton's principle, the governing equation and boundary conditions are derived based on Eringen's theory. The influence of nonlinear and nonlocal factors on axial vibrations was investigated separately for all three theories: Simple (ST), Rayleigh (RT) and Bishop (BT). Using different theories, the effects of inertia and shear on the internal resonances of gold nanorods were studied and compared in terms of twoto-one and three-to-one internal resonances. As the nonlocal parameter of the gold nanorod increases, the maximum nonlinear amplitude occurs. So, by adding nonlocal effects in a gold nanorod, the internal modal interactions resulting from the unique structure can be enhanced. It is worth noting that shear and inertial analysis have a significant effect on internal modal interactions in gold nanorods.

• Journal of the Korean Vacuum Society
• /
• v.15 no.2
• /
• pp.223-230
• /
• 2006

We have investigated the characteristics of hydrogen (H) plasma treated quantum dot infrared photodetectors (QDIPs). The structure used in this study consists of 3 stacked, self assembled $In_{0.5}Ga_{0.5}As/GaAs$ QD layer separated by GaAs barrier layers that were grown by molecular beam epitaxy. Optical characteristics of QDIPs, such as photoluminescence (PL) spectra and photocurrent spectra, have been studied and compared with each other for the as grown and H plasma treated QDIPs. H plasma treatment, resulted in the splitting of PL peak, which can be attributed to the redistribution of the size of QDs. The activation energies estimated from the temperature dependence of integrated PL intensity for as grown and H plasma treated QDIPs are found to be in good agreement with those determined from corresponding peaks of photocurrent spectra. It is also noted that photocurrent is detected up to 130 K for the H plasma treated QDIP, suggesting the future possibility for the development of infrared photodetectors with high temperature operation.

• Journal of Powder Materials
• /
• v.16 no.2
• /
• pp.138-145
• /
• 2009

The combination of focused ion beam (FIB) and 4 point probe nanomanipulator could make various nano manufacturing and electrical measurements possible. In this study, we manufactured individual ZnO nanowire devices and measured those electrical properties. In addition, tensile experiments of metallic Au and Pd nanowires was performed by the same directional alignment of two nanomanipulators and a nanowire. It was confirmed from I-V curves that Ohmic contact is formed between electrodes and nanomanipulators, which is able to directly measure the electrical properties of a nanowire itself. In the mechanical tensile test, Au and Pd nanowires showed a totally different fracture behavior except the realignment from <110> to <002>. The deformation until the fracture was governed by twin for Au and by slip for Pd nanowires, respectively. The crystallographic relationship and fracture mechanism was discussed by TEM observations.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.121-121
• /
• 2010

ZnO is a promising material for the application of high efficiency light emitting diodes with short wavelength region for its large bandgap energy of 3.37 eV which is similar to GaN (3.39 eV) at room temperature. The large exciton binding energy of 60 meV in ZnO provide provides higher efficiency of emission for optoelectronic device applications. Several ZnO/ZnMgO multiple quantum well (MQW) structures have been grown on various substrates such as sapphire, GaN, Si, and so on. However, the achievement of high quality ZnO/ZnMgO MQW structures has been somehow limited by the use of lattice-mismatched substrates. Therefore, we propose the optical properties of ZnO/ZnMgO multiple quantum well (MQW) structures with different well widths grown on lattice-matched ZnO substrates by molecular beam epitaxy. Photoluminescence (PL) spectra show MQW emissions at 3.387 and 3.369 eV for the ZnO/ZnMgO MQW samples with well widths of 2 and 5 nm, respectively, due to the quantum confinement effect. Time-resolved PL results show an efficient photo-generated carrier transfer from the barrier to the MQWs, which leads to an increased intensity ratio of the well to barrier emissions for the ZnO/ZnMgO MQW sample with the wider width. From the power-dependent PL spectra, we observed no PL peak shift of MQW emission in both samples, indicating a negligible built-in electric field effect in the ZnO/$Zn_{0.9}Mg_{0.1}O$ MQWs grown on lattice-matched ZnO substrates.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.1 s.343
• /
• pp.7-12
• /
• 2006

In this study, we developed irreversible and stable micro-size ferromagnetic structures utilizing hydrogenation and electron-beam lithography processes. The compositionally modulated (CM) Fe-Zr thin films that had average compositions $Fe_XZr_{100-x}$ with $x=65-85\%$ modulation periods of similar to 1 nm, and total thicknesses of similar to 100 m were prepared. The magnetic properties of CM Fe-Zr thin films were measured using a SQUID magnetometer, VSM and B-H loop tracer. After hydrogenation, the CM films exhibited larger magnetic moment increases than similar homogeneous alloy films for all compositions and かey showed largest increase in $Fe_{80}Zr_{20}$ composition. After aging in air at $300^{\circ}K$ the hydrogenated $Fe_{80}Zr_{20}$ CM films showed much larger magnetic moment increases, indicating that they relax to a stable, irreversible, soft magnetic state. The selective hydrogenation through electron-beam lithographed windows were performed after the circle shaped windows were prepared on $Fe_{80}Zr_{20}$ CM films by electron beam lithography. The hydrogenation through electron-beam resist and W lithographic techniques give a $49\%$ magnetic moment increase. This method can be applied to nano scale structures.

• Advances in nano research
• /
• v.10 no.2
• /
• pp.115-128
• /
• 2021

In this article, free vibration behavior of electro-magneto-thermo sandwich Timoshenko beam made of porous core and Graphene Platelet Reinforced Composite (GPLRC) in a thermal environment is investigated. The governing equations of motion are derived by using the modified strain gradient theory for micro structures and Hamilton's principle. The magneto electro are under linear function along the thickness that contains magnetic and electric constant potentials and a cosine function. The effects of material length scale parameters, temperature change, various distributions of porous, different distributions of graphene platelets and thickness ratio on the natural frequency of Timoshenko beam are analyzed. The results show that an increase in aspect ratio, the temperature change, and the thickness of GPL leads to reduce the natural frequency; while vice versa for porous coefficient, volume fractions and length of GPL. Moreover, the effect of different size-dependent theories such as CT, MCST and MSGT on the natural frequency is investigated. It reveals that MSGT and CT have most and lowest values of natural frequency, respectively, because MSGT leads to increase the stiffness of micro Timoshenko sandwich beam by considering three material length scale parameters. It is seen that by increasing porosity coefficient, the natural frequency increases because both stiffness and mass matrices decreases, but the effect of reduction of mass matrix is more than stiffness matrix. Considering the piezo magneto-electric layers lead to enhance the stiffness of a micro beam, thus the natural frequency increases. It can be seen that with increasing of the value of WGPL, the stiffness of microbeam increases. As a result, the value of natural frequency enhances. It is shown that in hc/h = 0.7, the natural frequency for WGPL = 0.05 is 8% and 14% less than its for WGPL = 0.06 and WGPL = 0.07, respectively. The results show that with an increment in the length and width of GPLs, the natural frequency increases because the stiffness of micro structures enhances and vice versa for thickness of GPLs. It can be seen that the natural frequency for aGPL = 25 ㎛ and hc/h = 0.6 is 0.3% and 1% more than the one for aGPL = 5 ㎛ and aGPL = 1 ㎛, respectively.

• Particle and aerosol research
• /
• v.6 no.3
• /
• pp.139-145
• /
• 2010

In this study, we investigated the particle formation during the deposition of borophosphosilicate glass (BPSG) and phosphosilicate glass (PSG) films in thermal chemical vapor deposition reactor using in-situ particle monitor (ISPM) and particle beam mass spectrometer (PBMS) which installed in the reactor exhaust line. The particle current and number count are monitored at set-up, stabilize, deposition, purge and pumping process step in real-time. The particle number distribution at stabilize step was measured using PBMS and compared with SEM image data. The PBMS and SEM analysis data shows the 110 nm and 80 nm of mode diameter for BPSG and PSG process, respectively.

• Journal of the Korean Ceramic Society
• /
• v.42 no.2 s.273
• /
• pp.117-122
• /
• 2005

Electron Beam Physical Vapor Deposition (EB-PVD) is a typical technology for thermal barrier coating with Yttria Stabilized Zirconia (YSZ) on aero gas turbine engine. In this study EB-PVD method was used to fabricate dense YSZ film on NiO-YSZ as a electrolyte of Solid Oxide Fuel Cell (SOFC). Dense YSZ films of -10 $\mu$m thickness showed nano surface structure depending on deposition temperature. Electrical conductivities of YSZ film and electric power density of the single cell were evaluated after screen- printing $LaSrCoO_3$ as a cathode.

• Nuclear Engineering and Technology
• /
• v.52 no.11
• /
• pp.2585-2593
• /
• 2020

Swift heavy ion (SHI) beam irradiation can generate desirable defects in materials by transferring sufficient energy to the lattice that favours huge possibilities in tailoring of materials. The effect of Ag¹⁵⁺ ion irradiation with energy 200 MeV on spray deposited V₂O₅ thin films of thickness 253 nm is studied at various ion doses from 5 × 10¹¹ to 1 × 10¹³ ions/㎠. The XRD results of pristine film confirmed orthorhombic structure of V₂O₅ and its average crystallite size was found to be 20 nm. The peak at 394 cm^-1 in Raman spectra confirmed O-V-O bonding of V₂O₅, whereas 917 cm^-1 arise because of distortion in stoichiometry by a loss of oxygen atoms. Raman peaks vanished completely above the ion fluence of 5 × 10¹² ions/㎠. Optical studies by UV-Vis spectroscopy shows decrement in transmittance with an increase in ion fluence up to 5 × 10¹² ions/㎠. The red shift is observed both in the direct and indirect band gaps until 5 × 10¹² ions/㎠. The surface topography of the pristine film revealed sheath like structure with randomly distributed spherical nano-particles. The roughness of film decreased and the density of spherical nanoparticles increased upon irradiation. Irradiation improved the conductivity significantly for fluence 5 × 10¹¹ ions/㎠ due to band gap reduction and grain growth.

• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.6
• /
• pp.795-804
• /
• 2007

Statement of problem. Nano-scale calcium-phosphate coating on the anodizing titanium surface using ion beam-assisted deposition (IBAD) has been recently introduced to improve the early osseointegration. However, not much is known about their surface characteristics that have influence on tissue-implant interaction. Purpose. This study was aimed to investigate microtopography, surface roughness, surface composition, and wettability of the titanium surface modified by the anodic oxidation and calcium phosphate coating using IBAD. Material and methods. Commercially pure titanium disks were used as substrates. The experiment was composed of four groups. Group MA surfaces represented machined surface. Group AN was anodized surface. Group CaP/AN was anodic oxidized and calcium phosphate coated surfaces. Group SLA surfaces were sandblasted and acid etched surfaces. The prepared titanium discs were examined as follows. The surface morphology of the discs was examined using SEM. The surface roughness was measured by a confocal laser scanning microscope. Phase components were analyzed using thin-film x-ray diffraction. Wettability analyses were performed by contact angle measurement with distilled water, formamide, bromonaphtalene and surface free energy calculation. Results. (1) The four groups showed specific microtopography respectively. Anodized and calcium phosphate coated specimens showed multiple micropores and tiny homogeneously distributed crystalline particles. (2) The order of surface roughness values were, from the lowest to the highest, machined group, anodized group, anodized and calcium phosphate deposited group, and sandblasted and acid etched group. (3) Anodized and calcium phosphate deposited group was found to have titanium and titanium anatase oxides and exhibited calcium phosphorous crystalline structures. (4) Surface wettability was increased in the order of calcium phosphate deposited group, machined group, anodized group, sandblasted and acid etched group. Conclusion. After ion beam-assisted deposition on anodized titanium, the microporous structure remained on the surface and many small calcium phosphorous crystals were formed on the porous surface. Nanoscale calcium phosphorous deposition induced roughness on the microporous surface but hydrophobicity was increased.