• Journal of the Microelectronics and Packaging Society
• /
• v.28 no.1
• /
• pp.1-12
• /
• 2021

Here, we introduce a laser-induced graphene synthesis technology and its applications for the electric/electronic device manufacturing process. Recently, the micro/nanopatterning technique of graphene has received great attention for the utilization of these new graphene structures, which shows progress developments at present with a variety of uses in electronic devices. Some examples of practical applications suggested a great potential for the tunable graphene synthetic manners through the control of the laser set-up, such as a selection of the wavelength, power adjustment, and optical techniques. This emerging technology has expandability to electric/electronic devices combined together with existed micro-packaging technology and can be integrated with the new processing steps to be applied for the operation in the fields of biosensors, supercapacitors, electrochemical sensors, etc. We believe that the laser-induced graphene technology introduced in this paper can be easily applied to portable small electronic devices and wearable electronics in the near future.

• Journal of Powder Materials
• /
• v.28 no.2
• /
• pp.143-149
• /
• 2021

In this study, (GaN)_1-x(ZnO)_x solid solution nanoparticles with a high zinc content are prepared by ultrasonic spray pyrolysis and subsequent nitridation. The structure and morphology of the samples are investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The characterization results show a phase transition from the Zn and Ga-based oxides (ZnO or ZnGa₂O₄) to a (GaN)_1-x(ZnO)_x solid solution under an NH3 atmosphere. The effect of the precursor solution concentration and nitridation temperature on the final products are systematically investigated to obtain (GaN)_1-x(ZnO)_x nanoparticles with a high Zn concentration. It is confirmed that the powder synthesized from the solution in which the ratio of Zn and Ga was set to 0.8:0.2, as the initial precursor composition was composed of about 0.8-mole fraction of Zn, similar to the initially set one, through nitriding treatment at 700℃. Besides, the synthesized nanoparticles exhibited the typical XRD pattern of (GaN)_1-x(ZnO)_x, and a strong absorption of visible light with a bandgap energy of approximately 2.78 eV, confirming their potential use as a hydrogen production photocatalyst.

• Science of Emotion and Sensibility
• /
• v.25 no.1
• /
• pp.67-78
• /
• 2022

Interest in bio-signal monitoring of wearable devices is increasing significantly as the next generation needs to develop new devices to dominate the global market of the information and communication technology industry. Accordingly, this research developed a resistive textile strain sensor through a wetting process in a single-wall carbon nanotube dispersion solution using an E-Band with low hysteresis. To measure the resistance signal in the E-Band to which electrical conductivity is applied, a universal material tester, an Arduino, and LCR meters that are microcontroller units were used to measure the resistance change according to the tensile change. To effectively handle various noises generated due to the characteristics of the fabric textile strain sensor, the filter performance of the sensor was evaluated using the moving average filter, Savitsky-Golay filter, and intermediate filters of signal processing. As a result, the reliability of the filtering result of the moving average filter was at least 89.82% with a maximum of 97.87%, and moving average filtering was suitable as the noise filtering method of the textile strain sensor.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.32 no.5
• /
• pp.175-182
• /
• 2022

Rare-earth elements were doped with Mg to enhance the temperature stability of dielectric properties of BaTiO₃ for its application to MLCC (Multi-Layer Ceramic Capacitor). The additives strongly affect both grain growth and densification behaviors during sintering, and hence dielectric properties. The additive effects therefore should be examined in each system with different additives. This study investigated the crystal structure, grain growth and densification behaviors and related variations in dielectric constant with respect to sintering temperature. Dielectric constant appears to be varied with grain size in a temperature range between 1200 and 1300℃, suggesting the importance of grain size control. The temperature dependence of grain size variation was well explained by an established theory correlating the grain growth behavior with grain boundary structure. This accordance provides a basis for sintering technique to control grain growth thus to improve dielectric constant in rare-earth doped BaTiO₃.

• Journal of Powder Materials
• /
• v.29 no.1
• /
• pp.47-55
• /
• 2022

Tungsten carbide is widely used in carbide tools. However, its production process generates a significant number of end-of-life products and by-products. Therefore, it is necessary to develop efficient recycling methods and investigate the remanufacturing of tungsten carbide using recycled materials. Herein, we have recovered 99.9% of the tungsten in cemented carbide hard scrap as tungsten oxide via an alkali leaching process. Subsequently, using the recovered tungsten oxide as a starting material, tungsten carbide has been produced by employing a self-propagating high-temperature synthesis (SHS) method. SHS is advantageous as it reduces the reaction time and is energy-efficient. Tungsten carbide with a carbon content of 6.18 wt % and a particle size of 116 nm has been successfully synthesized by optimizing the SHS process parameters, pulverization, and mixing. In this study, a series of processes for the high-efficiency recycling and quality improvement of tungsten-based materials have been developed.

• Journal of the Microelectronics and Packaging Society
• /
• v.30 no.4
• /
• pp.86-90
• /
• 2023

The packaging of electronic devices performs a protective function to ensure that their durability and reliability are not affected by changes in the operating environment caused by external factors. Recent advances in materials have led to ongoing research into bonded packaging of heterogeneous materials such as polymers and inorganic materials in electronic devices. In this packaging process, it is important to have a binding that joins the materials and ensures the operating environment, which includes adhesion to the substrate, corrosion and oxidation resistance through moisture removal, and durability. In this study, the hygroscopicity of the coating layer by modifying the polymer surface based on PVA was evaluated by controlling and measuring the contact angle, and the adhesion was confirmed by applying water-based ink and testing according to ASTM_D3363. For the durability of the polymer surface, the IPL post-treatment process was used to improve the hardness and toughness against applied voltage, and the pencil hardness test and nanoindentation test were conducted. Through this, we analyzed and proposed solutions to ensure the reliability and durability of polymer devices in polymer microfabrication against environmental factors such as moisture, temperature fluctuations and adhesion, and surface abrasion.

• Korean Chemical Engineering Research
• /
• v.62 no.1
• /
• pp.13-18
• /
• 2024

To develop flexible electrode materials for wearable devices, we investigated the electrochemical characteristics of carbon fibers tow according to pretreatment. And an electrochemical non-enzymatic sensor was fabricated using glucose as a target. The carbon fibers tow was pretreated through desizing and activation processes, and activation was performed in two ways: chemical oxidation and electrochemical oxidation. Surface morphology of carbon fibers tow samples was observed by SEM and their electrochemical characteristics and sensing performance were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Carbon fibers tow samples showed improved electrochemical properties such as reduced R_et, ΔE_p, and increased I_p through pretreatment. And similar electrochemical properties were obtained with both activation methods. We selected electrochemically activated carbon fibers tow as the final electrode material for application of electrochemical sensor. The non-enzymatic glucose sensor based on this electrode has an enhanced sensitivity of 0.744 A/mM (in a linear range of 0.09899~3.75423 mM) and 0.330 mA/mM (3.75423~50 mM), respectively. Through this study, the possibility of using carbon fibers tow was confirmed as an electrode material. It is expected to be used as basic research for development of high-performance flexible electrode materials.

• Journal of the Korean Vacuum Society
• /
• v.17 no.6
• /
• pp.528-537
• /
• 2008

60 nm and 20 nm thick hydrogenated amorphous silicon(a-Si:H) layers were deposited on 200 nm $SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by an e-beam evaporator. Finally, 30 nm-Ni/(60 nm and 20 nm) a-Si:H/200 nm-$SiO_2$/single-Si structures were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 40 sec. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide from the 60 nm a-Si:H substrate showed low sheet resistance from $400^{\circ}C$ which is compatible for low temperature processing. The nickel silicide from 20 nm a-Si:H substrate showed low resistance from $300^{\circ}C$. Through HRXRD analysis, the phase transformation occurred with silicidation temperature without a-Si:H layer thickness dependence. With the result of FE-SEM and TEM, the nickel silicides from 60 nm a-Si:H substrate showed the microstructure of 60 nm-thick silicide layers with the residual silicon regime, while the ones from 20 nm a-Si:H formed 20 nm-thick uniform silicide layers. In case of SPM, the RMS value of nickel silicide layers increased as the silicidation temperature increased. Especially, the nickel silicide from 20 nm a-Si:H substrate showed the lowest RMS value of 0.75 at $300^{\circ}C$.

• Journal of the Microelectronics and Packaging Society
• /
• v.31 no.2
• /
• pp.54-62
• /
• 2024

SICM (Scanning Ion Conductivity Microscopy) is a technique for measuring surface topography in an environment where electrochemical reactions occur, by detecting changes in ion conductivity as a nanopipette tip approaches the sample. This study includes an investigation of the current response curve, known as the approach curve, according to the distance between the tip and the sample. First, a simulation analysis was conducted on the approach curves. Based on the simulation results, then, several measuring experiments were conducted concurrently to analyze the difference between the simulated and measured approach curves. The simulation analysis confirms that the current squeezing effect occurs as the distance between the tip and the sample approaches half the inner radius of the tip. However, through the calculations, the decrease in current density due to the simple reduction in ion channels was found to be much smaller compared to the current squeezing effect measured through actual experiments. This suggests that ion conductivity in nano-scale narrow channels does not simply follow the Nernst-Einstein relationship based on the diffusion coefficients, but also takes into account the fluidic hydrodynamic resistance at the interface created by the tip and the sample. It is expected that SICM can be combined with SECM (Scanning Electrochemical Microscopy) to overcome the limitations of SECM through consecutive measurement of the two techniques, thereby to strengthen the analysis of electrochemical surface reactivity. This could potentially provide groundbreaking help in understanding the local catalytic reactions in electroless plating and the behaviors of organic additives in electroplating for various kinds of patterns used in semiconductor damascene processes and packaging processes.

• Journal of the Microelectronics and Packaging Society
• /
• v.24 no.4
• /
• pp.79-84
• /
• 2017

The solar cells should be protected from the moisture and oxygen in order to sustain the properties and reliability of the devices. In this research, we prepared the protection films on the flexible plastic substrates by spray coating method using organic-inorganic hybrid solutions. The protection characteristics were studied depending on the various process conditions (nozzle distance, thicknesses of the coatings, film structures). The organic-inorganic solutions for the protection film layer were synthesized by addition of $Al_2O_3$ ($P.S+Al_2O_3$) and $SiO_2$ ($P.S+SiO_2$) nano-powders into PVA (polyvinyl alcohol) and SA (sodium alginate) (P.S) organic solution. The optical transmittances of the protection film with the thicknesses of $5{\mu}m$ showed 91%. The optical transmittance decreased from 81.6% to 73.6% with the film thickness increased from $78{\mu}m$ to $178{\mu}m$. In addition, the protective films were prepared on the PEN (polyethylene naphthalate), PC (polycarbonate) single plastic substrates as well as the Acrylate film coated on PC substrate (Acrylate film/PC double layer), and $Al_2O_3$ film coated on PEN substrate ($Al_2O_3$ film/PEN double layer) using the $P.S+Al_2O_3$ organic-inorganic hybrid solutions. The optimum protection film structure was studied by means of the measurements of water vapor transmittance rate (WVTR) and surface morphology. The protective film on PEN/$Al_2O_3$ double layer substrate showed the best water protective property, indicating the WVTR value of $0.004gm/m^2-day$.