• Transactions on Electrical and Electronic Materials
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• v.10 no.4
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• pp.131-134
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• 2009

The electrical properties and the microstructure of nitrogen-doped poly 3C-SiC films used for micro thermal sensors were studied according to different thicknesses. Poly 3C-SiC films were deposited by LPCVD (low pressure chemical vapor deposition) at $900^{\circ}C$ with a pressure of 4 torr using $SiH_2Cl_2$ (100%, 35 sccm) and $C_2H_2$ (5% in $H_2$, 180 sccm) as the Si and C precursors, and $NH_3$ (5% in $H_2$, 64 sccm) as the dopant source gas. The resistivity of the poly SiC films with a 1,530 ${\AA}$ thickness was 32.7 ${\Omega}-cm$ and decreased to 0.0129 ${\Omega}-cm$ at 16,963 ${\AA}$. The measurement of the resistance variations at different thicknesses were carried out within the $25^{\circ}C$ to $350^{\circ}C$ temperature range. While the size of the resistance variation decreased when the films thickness increased, the linearity of the resistance variation improved. Micro heaters and RTD sensors were fabricated on a $Si_3N_4$ membrane by using poly 3C-SiC with a 1um thickness using a surface MEMS process. The heating temperature of the SiC micro heater, fabricated on 250 ${\mu}m$${\times}$250 ${\mu}m$ $Si_3N_4$ membrane was $410^{\circ}C$ at an 80 mW input power. These 3C-SiC heaters and RTD sensors, fabricated by surface MEMS, have a low power consumption and deliver a good long term stability for the various thermal sensors requiring thermal stability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.299-302
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• 2001

In this study, we are studied the electrical conduction and dielectric breakdown properties of insulating varnish. In order to analyze the molecular structure and physical properties of insulating varnishs, FT-lR was used. As the result, it can be confirmed that the peak of alcoholic group appeared in wavenumbers 3452[cm$\^$-1], the peak of =CH appeared in 3080[cm$\^$-1] and the peak of -CH appeared in 2919[cm$\^$-1] respectively. The following results were obtained from electrical properties of insulating varnish. The amplitude of current density was decreased by thickness increasing and the current density was effected by the thermal energy from external due to temperature increasing. In study temperature dependence of dielectric strength, the specimen of 10[$\mu\textrm{m}$] thickness was measurement from room temperature to 180[$^{\circ}C$]. It is confirmed that the temperature regions below 60[$^{\circ}C$] is due to electron avalanche breakdown and the temperature regions over 60[$^{\circ}C$] is due to free volume breakdown which makes electron movements easy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1071-1076
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• 2003

The nonlinear properties and their stability of ZPCCD- based varistors, which are composed of ZnO P $r_{6}$ $O_{ll}$ - CoO-C $r_2$ $O_3$-D $y_2$ $O_3$-based ceramics, were investigated in the D $y_2$ $O_3$ content range of 0.0∼2.0 mol%. The incorporation of D $y_2$ $O_3$ greatly affected the nonlinear properties and the best nonlinearity was obtained from 0.5 mol% D $y_2$ $O_3$ with nonlinear exponent of 66.6 and leakage current of 1.2 $\mu$A. Further addition of D $y_2$ $O_3$ deteriorated the nonlinear properties. In stability against DC accelerated aging stress state: 0.95 $V_{1mA}$/15$0^{\circ}C$/24 h, the 0.5 mol％ D $y_2$ $O_3$-doped varistor exhibited the highest stability, in which the variation rate of varistor voltage and nonlinear exponent are -1.9% and 10.5%, respectively. The remainder varistors resulted in thermal runaway due to low density of ceramics.s.s.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.233-240
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• 2021

For the production of neodymium-doped zinc sulfide thin films in various amounts, zinc sulfide and neodymium were simultaneously deposited using an RF magnetron sputtering equipment to form a thin films, and rapid thermal annealing was performed at 400℃ for 30 minutes as a post-treatment process. The structure, shape, and optical properties of ZnS thin films having various neodymium doping contents (0.35at.%, 1.31at.%, 1.82at.% and 1.90at.%) were studied. The X-ray diffraction pattern was grown to a (111) cubic structure in all thin films. The surface and structural morphology of the thin films due to the neodymium doping content was explained through SEM and AFM images. Only elements of Zn, S, and Nd that do not contain other impurities were identified through EDAX. The transmittance and band gap of the prepared thin films were confirmed using the UV-vis spectrum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.127-130
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• 2005

The properties of phosphorus doped ZnO multilayer thin films deposited on (001) sapphire substrates by pulsed laser deposition (PLD) were investigated by using annealing treatment at various annealing temperature after deposition. The phosphorus doped ZnO multilayer was composed of phosphorus doped ZnO layer and two pure ZnO layers on sapphire substrate. The structural. electrical and optical properties of the ZnOthin films were measured by X-ray diffraction (XRD). Hall measurements and photoluminescence (PL). As the annealing temperature optimized. the electrical properties of the ZnO multilayer showed a electron concentration of $1.56{\times}10^{16}/cm^3$, a resistivity of 17.97 ${\Omega}cm$. It was observed the electrical property of the film was changed by dopant activation effect as thermal annealing process

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2381-2384
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• 2008

The heat exchange between the Borehole Heat Exchanger(BHE) and the surrounding ground depends directly on ground thermal conductivity k at the certain site. The k is thus a key parameter in designing BHE and coupled geothermal heat pump systems. Currently, although a thermal hydraulic Response Test(TRT) is mostly used in practice, the thermal hydraulic TRT needs additional power and is generally time-consuming. A new, simple wireless probe for hi-speed k determination was introduced in this paper. This technique using a wireless probe is less time-consuming and requires no external source of energy for measurement and predicts local thermal properties by measuring soil temperatures along the depth. Measured temperature data along the depth was analyzed. As a result, the electronic wireless probe can replace the conventional hydraulic TRT method after carrying out the additional research on a lot of local heat flow, etc.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.34-37
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• 2001

In this study, the capacitance-voltage properties of $(Sr_{1-x}\cdot Ca_x)TiO_3(0.05{\leq}x{\leq}0.20)$-based grain boundary layer ceramics were investigated. The ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were $1480\sim1500^{\circ}C$ and 4 hours. respectively. The 2nd phase formed by the thermal diffusion of CuO from the surface leads to very excellent dielectric properties, that is, ${\varepsilon}_r$ >50000, tan$\delta$ <0.05, ${\Delta}C$ < ${\pm}10%.$ The capacitance is almost unchanged below about 20[V] but it decreases slowly about 20[V]. The results of the capacitance-voltage properties indicated that the grain boundary was composed of the continuous insulating layers.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.665-670
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• 2020

Buffer layer in CIGS thin-film solar cells improves energy conversion efficiency through band alignment between the absorption layer and the window layer. ZnS is a non-toxic II-VI compound semiconductor with direct-transition band gaps and n-conductivity as well as with excellent lattice matching for CIGS absorbent layers. In this study, the structural and optical properties of ZnS thin films, deposited by RF magnetron sputtering method and subsequently performed by the rapid thermal annealing treatment, were investigated for the buffer layer. The zincblende cubic structures along (111), (220), and (311) were shown in all specimens. The rapid thermal annealed specimens at the relatively low temperatures were polycrystalline structure with the wurtzite hexagonal structures along (002). Rapid thermal annealing at high temperatures changed the polycrystalline structure to the single crystal of the zincblende cubic structures. Through the chemical analysis, the zincblende cubic structure was obtained in the specimen with the ratio of Zn/S near stoichiometry. ZnS thin film showed the shifted absorption edge towards the lower wavelength as annealing temperature increased, and the mean optical transmittance in the visible light range increased to 80.40% under 500℃ conditions.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.73-74
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• 2006

Carbon nanotubes (CNTs) have recently attracted great attention because of their excellent physical properties, such as high mechanical strength, thermal stability, and electronic properties. These useful properties of carbon nanotubes make themselves good candidates for various application field, such as a transistor, battery, field emission display, nanoscale inter-connects, and so on. Gas-phase techniques offer the unique ability to synthesize well-oriented arrays of CNTs. However, it is seldom reported that the pressure influences on the growth of CNTs under low substrate temperature. In this work, the effect of the working pressure and the influence of the catalyst preparation on the properties of CNTs grown by microwave plasma chemical vapor deposition (MPCVD) were investigated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.25.1-25.1
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• 2011

Over the past few decades, metallic nanoparticles (NPs) have been of great interest due to their unique mesoscopic properties which distinguish them from those of bulk metals; such as lowered melting points, greater versatility that allows for more ease of processability, and tunable optical and mechanical properties. Due to these unique properties, potential opportunities are seen for applications that incorporate nanomaterials into optical and electronic devices. Specifically, the development of metallic NPs has gained significant interest within the electronics field and technological community as a whole. In this study, gold (Au) pads for surface finish in electronic package were developed by inkjet printing of Au NPs. The microstructures of inkjet-printed Au film were investigated by various thermal treatment conditions. The film showed the grain growth as well as bonding between NPs. The film became denser with pore elimination when NPs were sintered under gas flows of $N_2$-bubbled through formic acid ($FA/N_2$) and $N_2$, which resulted in improvement of electrical conductance. The resistivity of film was 4.79 ${\mu}{\Omega}$-cm, about twice of bulk value. From organic anlayses of FTIR, Raman spectroscopy, and TGA, the amount of organic residue in the film was 0.43% which meant considerable removal of the solvent or organic capping molecules. The solder ball shear test was adopted for solderability and shear strength value was 820 gf (1 gf=9.81 mN) on average. This shear strength is good enough to substitute the inkjet-printed Au nanoparticulate film for electroplating in electronic package.