• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.36 no.5
• /
• pp.525-530
• /
• 2023

Stretchable piezoelectric energy harvester (S-PEHs) based on composite materials are considered one of the potential candidates for realizing wearable self-powered devices for smart clothing and electronic skin. However, low energy conversion performance and expensive stretchable electrodes are major bottlenecks hindering the development and application of S-PEHs. Here, we fabricated the S-PEH by adopting the piezoelectric composites with enhanced stress transfer properties and kirigami-patterned textile electrodes. The optimum contents of piezoelectric BaTiO₃ nanoparticles inside the carbon nanotube/ecoflex composite were selected as 30 wt% considering the trade-off between stretchability and energy harvesting performance of the device. The final S-PEH shows an output voltage and mechanical stability of ~5 V and ~3,000 cycles under repeated 150% of tensile strain, respectively. This work presents a cost-effective and scalable way to fabricate stretchable piezoelectric devices for self-powered wearable electronic systems.

• Journal of the Korean Society for Heat Treatment
• /
• v.36 no.4
• /
• pp.193-197
• /
• 2023

Transparent and conducting titanium (Ti) doped indium oxide (TIO) thin films were deposited on the poly-imide (PI) substrate with radio frequency magnetron sputtering and then electron irradiation was conducted on the TIO film's surface to investigate the effect electron irradiation on the crystallization and opto-electrical properties of the films. All x-ray diffraction (XRD) pattern showed two diffraction peaks of the In₂O₂ (431) and (444) planes with regardless of the electron beam irradiation energy. In the AFM analysis, the surface roughness of as deposited films was 3.29 nm, while the films electron irradiated at 700 eV, show a lower RMS roughness of 2.62 nm. In this study, the FOM of as deposited TIO films is 6.82 × 10^-3 Ω^-1, while the films electron irradiated at 500 eV show the higher FOM value of 1.0 × 10^-2 Ω^-1. Thus, it is concluded that the post-deposition electron beam irradiation at 500 eV is the one of effective methods of crystallization and enhancement of opto-electrical performance of TIO thin film deposited on the PI substrate.

• Journal of the Microelectronics and Packaging Society
• /
• v.23 no.2
• /
• pp.65-71
• /
• 2016

In this study, Antimony Tin Oxide (ATO) ion storage layer and $TiO_2$ working electrode were fabricated using Nano Particle Deposition System. NPDS is the cutting-edge technology among the dry deposition methods. Accelerated particles are deposited on the substrate through the nozzle using NPDS. The thicknesses for coated layers were measured and layer's morphology was acquired using SEM. The fabricated electrochromic cell's transmittance was measured using UV-Visible spectrometer and power source at 630 nm. As a result, the integrated electrochromic/DSSC hybrid system was successfully fabricated as an energy harvesting system. The fabricated electrochromic cell was self-operated using DSSC as a power source. In conclusion, the electrochromic cell was operated for 500 cycles, with 49% of maximum transmittance change. Also the photovoltaic efficiency for DSSC was measured to be 2.55% while the electrochromic cell on the integrated system had resulted in 26% of maximum transmittance change.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.25 no.2
• /
• pp.183-190
• /
• 2009

The aim of this study is to find the condition of forming the favorable nanotubes by anodizing with NaF and $H_3PO_4$. Machined Ti discs were used for anode, and Platinum net was used for cathode. For electrolyte, $H_3PO_4$ and NaF solution were mixed. We controlled voltage, electrolyte concentration, anodizing time and formed nanotubes on Ti discs. After that, these were washed with distilled water for 24 hours and dried in the $40^{\circ}C$ oven for 24 hours. The surface structure of specimens were analyzed. The results were as follows : At 0.5 wt % NaF, according as increasing voltage and anodizing time, early state of nucleating pores were generated. At 1.0 wt % NaF, 20 V, 20 & 25 min, well-formed nanotubes were observed. At 1.0 wt % NaF, 30 V, structure of nanotube became bigger and interconnected. At 2.0 wt % NaF, no nanotubes were formed and it was unrelated with voltage and time. At 1.0 wt % NaF, 20 V, 20 - 25 min, well-ordered nanotubes were generated on Ti discs. For the formation of favorable nanotubes, it is considered that proper parameters such as electrolyte concentration, voltage, anodizing time are necessary according to the kind of electrolytes.

• Korean Journal of Materials Research
• /
• v.11 no.5
• /
• pp.339-344
• /
• 2001

An all solid-state thin film supercapacitor (TFSC) with Co$_3$O$_4$/LiPON/Co$_3$O$_4$ structure was fabricated on Pt/Ti/Si substrate using Co$_3$O$_4$ thin film electrode. Each Co$_3$O$_4$ film was grown by reactive dc reactive magnetron sputtering with increasing $O_2$/[Ar+O$_2$] ratio. Amorphous LiPON electrolyte film was deposited on Co$_3$O$_4$/Pt/Ti/Si in pure nitrogen ambient by using reactive rf magnetron sputtering. The electrochemical behavior of the Co$_3$O$_4$/LiPON/Co$_3$O$_4$ multi-layer structures exhibits a behavior of a bulk-type supercapacitor, even though much lower capacity (from 5 to 25 mF/$\textrm{cm}^2$-$\mu\textrm{m}$) than that of the bulk one. It was found that the TFSC showed a fairly constant discharge capacity with a constant current of 50 $\mu\textrm{A}/\textrm{cm}^2$ at the cut-off voltage 0-2V during 400 cycles. It is shown that the electrochemical behavior of the Co$_3$O$_4$/LiPON/Co$_3$O$_4$ TFSC is dependent upon the sputtering gas ratio. The capacity dependency of electrode films on different gas ratios was explained by different structural, electrical, and surfacical properties.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.47 no.8
• /
• pp.1-6
• /
• 2010

We report on the electrical properties of Ti/Al/Ni/Au (20 nm/ 150 nm/ 30 nm/ 100 nm) Ohmic contacts and the anisotropic conductivity of n-type ${\alpha}$-plane ([11-20]) GaN grown on $\gamma$-plane ([1-102]) sapphire substrates. The Ti/Al/Ni/Au Ohmic contacts and their sheet resistances are characterized by using the transfer length method (TLM) as a function of azimuthal angles. It is found that the specific contact resistance does not depend on the axis orientation and there are significant electrical anisotropy in ${\alpha}$-plane GaN films on $\gamma$-plane sapphire substrates, and the sheet resistance varies with azimuthal angles. The sheet resistance values in the direction parallel to m-axis [1-100] are 25% ~ 75% lower than those parallel to c-axis [0001] directions. Thus, Basal stacking faults (BSFs) are offered as a feasible source of the anisotropic mobility in defected m-axis direction because the band-edge discontinuities owing to the differential band gap structure.

• Korean Chemical Engineering Research
• /
• v.46 no.1
• /
• pp.131-136
• /
• 2008

Silica- or titania-filled poly (vinylidene fluoride-co-hexafluoropropylene)-based polymer electrolytes were prepared by phase inversion technique using N-methyl-2-pyrrolidone and dimethyl acetamide as solvent and water as non-solvent. The polymer electrolytes were adopted to the lithium metal polymer battery using high-capacity cathode $Li[Ni_{0.15}Co_{0.10}Li_{0.20}Mn_{0.55}]O_2$ and lithium metal anode. After the repeated charge-discharge test for the cell, it was proved that the cell adopting the polymer electrolyte based on the phase-inversion membrane containing 40~50 wt% silica showed the highest discharge capacity (180 mAh/g) until 80th cycle and then abrupt capacity fade was just followed. The capacity fade might be due to the deposition of lithium dendrite on the polymer electrolyte, in which the capacity retention was no longer sustainable.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.8
• /
• pp.8-15
• /
• 2007

In this paper, we fabricated the field emitter display using oxidized porous polysilicon(OPPS). Their field emission characteristics and the brightness were investigated for each pixel. The OPPS emitter was operated to each pixel using passive matrix for application of large panel display. We set up the proper thickness and width of upper electrode. The fine structure of OPPS was analyzed and the field emission characteristics of each pixel were investigated. As a result of field emission characteristics of different upper electrode thickness and width, we confirmed that the most efficient thickness was 2nm/7nm and increased the emission efficiency over the width of 2.5 mm. Even if field emission characteristics of each pixel was a little different but we confirmed the same leakage current and emission current, emission efficiency at each pixel. The leakage current and emission current was decreased according to the time increases but all of each pixel were uniformly decreased. We confirmed that the brightness of each pixel was not different and the brightness of OPPS field emitter was 700 cd/m2 at the Vps=20 V. Accordingly, the patterned OPPS field emitter can be applied to high quality field emission display devices.

• Journal of the Korean Vacuum Society
• /
• v.11 no.3
• /
• pp.183-188
• /
• 2002

In the present study AI$(CH_3)_3)$films were deposited by the ALD technique using trimethylaluminum(TMA) and ozone to improve the quality of the AI$(CH_3)_3)$ films, since the $OH^-$ radicals existing in the AI$(CH_3)_3)$ films deposited using TMA and $H_2O$ degrade the physical and the dielectric properties of the AI$(CH_3)_3)$ film. The XPS analysis results indicate that the $OH^-$ radical concentration in the AI$(CH_3)_3)$film deposited using $O_3$is lower than that using $H_2O$. The etch rate of the AI$(CH_3)_3)$film deposited using $O_3$is also lower than that using $H_2O$, suggesting that the chemical inertness of the former is better than the latter. The MIS capacitor fabricated with the TiN conductor and the $Al_2$O$_3$dielectrics formed using $O_3$offers lower leakage current, better insulating property and smaller flat band voltage shift $({\Delta}V_{FB})$.

• Korean Journal of Materials Research
• /
• v.8 no.12
• /
• pp.1170-1175
• /
• 1998

PZT films without lower electrode were deposited on the highly doped Si(100) substrate with MgO buffer layer (Mgo/si) by RF magnetron sputtering method followed by the rapid thermal annealing at $650^{\circ}C$ . We investigated the dependences of the crystalline and electrical properties on the MgO thickness and the RTA post annealing. The PZT films on bare Si (without MgO) showed pyrochlore crystal structure while those on MgO(50 )/Si substrates showed the typical perovskite crystal structures. From SEM and AES analysis, the thickness of PZT films was about 7000 showing relatively smooth interface. The depth profiles indicated that atomic species were distributed homogeneously in the PZT/MgO/Si substrate. The dielectric constant($\varepsilon_{r}$ ) and remanent polarization(2Pr) were about 300 and $14\mu$C/$\textrm{cm}^2$;, respectively. The leakage current was about $3.2\mu$/A$\textrm{cm}^2$.