• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.139-144
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• 2005

A rigorous research is underway in our team, for the design and development of high figure of merits (ZT= 1.5${\sim}$2.0) micro-thermoelectric coolers. This paper discusses the fabrication process that we are using for developing the $Sb_2Te_3-Bi_2Te_3$ micro-thermoelectric cooling modules. It describes how to obtain the mechanical properties of the thin film TEC elements and reports the results of an equation-based multiphysics modeling of the micro-TEC modules. In this study the thermoelectric thin films were deposited on Si substrates using co-sputtering method. The physical mechanical properties of the prepared films were measured by nanoindentation testing method while the thermal and electrical properties required for modeling were obtained from existing literature. A finite element model was developed using an equation-based multiphysics modeling by the commercial finite element code FEMLAB. The model was solved for different operating conditions. The temperature and the stress distributions in the P and N elements of the TEC as well as in the metal connector were obtained. The temperature distributions of the system obtained from simulation results showed good agreement with the analytical results existing in literature. In addition, it was found that the maximum stress in the system occurs at the bonding part of the TEC i.e. between the metal connectors and TE elements of the module.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.7
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• pp.50-57
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• 1989

Tapered etching of polysilicon films has been achieved by implanting phosphorus ions into the polysilicon film and using plasma etch in either $CF_4-O_2\;or\;SF_6$. A two-step plasma etching method is also proposed to control the taper angle of the etched edge without changing the implantion conditions. The taper angle is determined by the ratio of the etch rate of the undamaged region to that of the damaged top region of the polysilicon layer. The ratio is found to be dependent on the implantion dose, the implantion energy and the anisotropy of etching. The minimum angle in our experiments is about $10^{\circ}$. When the two-step etching method is employed, the taper angles can be controlled from the minimum angle up to about $55^{\circ}$.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.57-62
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• 2014

Using flexible bismaleimide-triazine co-polymer as a substrate, inkjet-printed Cu films were also investigated for low-cost and process feasibility of flexible electronics. After annealing at $200^{\circ}C$ for 1 h under various reducing ambient, surface color was changed to red and electrical resistivity was decreased to the level of conductor under formic acid ambient. However, its resistivity was much higher than conventional copper films due to surface crack. In order to reduce the residual film stress after annealing, additional isothermal treatment was inserted before anneal hiring the stress relaxation applied in processes of amorphous materials. As a result, no surface crack was observed and electrical resistivity of $3.4{\mu}{\Omega}cm$ was measured after annealing at $230^{\circ}C$ with stress relaxation while electrical resistivity of $7.4{\mu}{\Omega}cm$ was observed after normal annealing without relaxation. The effect of stress relaxation was also confirmed by observing surface crack after decreasing the relaxation time to 0 min.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.417-427
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• 1992

Silicon ion implantation was performed to LPCVD amorphous Si films and the low temperature annealing process followed with various conditions to find the optimal physical properties by studying recrystallization behavior. The uniformity of the recrystallized films was inspected by optical microscopy and for this purpose, new KOH: (IPA) : $H_2$O: $K_2$C${r_2}{O_7}$, etchant was developed. XRD and TEM results showed that the crystallites were grown as a form of dendrite with (111) preferred orientation, and the grain size was increased with dose concentration. The maximum grain size was obtained when the 3${\times}{10^{15}}$c$m^2$ implanted amorphous Si film was recrystallized at 55 $0^{\circ}C$for more than 40 hrs and at this condition the grain size was 3.2${\mu}$m.

• Korean Journal of Materials Research
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• v.16 no.5
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• pp.302-307
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• 2006

The formation and processing of organic insulators on the device performance have been studied in the fabrication of organic thin film transistors (OTFTs). The series of polyvinyls, poly-4-vinyl phenol(PVP) and polyvinyltoluene (PVT), were used as solutes and propylene glycol monomethyl ether acetate(PGMEA) as a solvent in the formation of organic insulators. The cross-linking of organic insulators was also attempted by adding the thermosetting material, poly (melamine-co-formaldehyde) as a hardener in the compound. The electrical characteristics measured in the metal-insulator-metal (MIM) structures showed that insulating properties of PVP layers were generally superior to those of PVT layers. Among the layers of PVP series: PVP(10 wt%) copolymer, 5 wt% cross-linked PVP(10 wt%), PVP(20 wt%) copolymer, 5 wt% cross-linked PVP(20 wt%) and 10 wt% cross-linked PVP(20 wt%), the 10 wt% cross-linked PVP(20 wt%) layer showed the lowest leakage current characteristics. Finally, inverted staggered OTFTs using the PVP(20 wt%) copolymer, 5 wt% cross-linked PVP(20 wt%) and 10 wt% cross-linked PVP(20 wt%) as gate insulators were fabricated on the polyether sulphone (PES) substrates. In our experiments, we could obtain the maximum field effect mobility of 0.31 $cm^2/Vs$ in the device from 5 wt% cross-linked PVP(20 wt%) and the highest on/off current ratio of $1.92{\times}10^5$ in the device from 10 wt% cross-linked PVP(20 wt%).

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.6
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• pp.846-857
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• 1998

The purpose of this study was to compare the fitness of the IPS Empress ceramic crowns according to margin type such as bevel, shoulder, rounded shoulder, shoulder with bevel, rounded shoulder with bevel and grooved bevel. After 10 experimental dies were constructed for each group, the IPS Empress ceramic crowns were fabricated on the dies, cemented with resin cement(Bistite resin cement, Tokuyama Soda Co. Ltd., Japan) and embeded in clear epoxy resin. Each specimen was sectioned with a low speed diamond saw in both the faciopalatal and the mesiodistal direction. The cement film thickness was measured with a measuring microscope. The obtained results were as follows : 1. The fitness at the external margin was good in the following order: rounded shoulder(28.99), shoulder with bevel(31.33), grooved bevel(31.79), rounded shoulder with bevel(34.65), bevel(35.02) and shoulder(35.08). However there is no significant statistical difference. 2. The fitness at the internal margin of bevel(25.75), rounded shoulder(31.24), shoulder with bevel(32.07) and rounded shoulder with bevel(34.45) was better than that of shoulder(47.98). 3. The fitness at the axial surface of bevel(26.58) was better than that of shoulder(49.59). 4. The fitness at the central fossa was good in the following order: shoulder with bevel(38.88), grooved bevel(40.46) rounded shoulder with shoulder(46.29), shoulder(48.91), bevel(49.47) and rounded bevel(52.07). However there is no significant statistical difference. 5. Overall fitness of bevel(29.71), rounded shoulder(32.49) and shoulder with bevel(34.47) was better than that of shoulder(44.73).

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.6
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• pp.1304-1309
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• 1999

The respiratory characteristics and quality attributes of mature green mume fruits as influenced by modified atmosphere packaging(MAP) conditions during storage at 25oC for 8 days were investigated. The quality attributes of mume fruits were evaluated in terms of fresh weight loss, physiological injury and yellowing. The packaging materials used for MAP were low density polyethylene(LDPE) films with various different thicknesses. Yellowing and fresh weight loss of mume fruits were noticeably reduced by the packaging treatments with LDPE A and B. The physiological injury of the fruits during storage was found to be more severe in LDPE C than others. For LDPE A and B, the oxygen and carbon dioxide contents within the packages of Mume fruits maintained at the levels of 2~3% and 7~8%, respectively. With respect to visual quality, MAP prolonged the shelf life of the fruits much longer compared with the unsealed control. From the experimental results, it is suggested that the LDPE films with the gas trans mission rates of about 2,100 O2 ml/m2.day.atm and 6,700 CO2 ml/m2.day.atm would be proper for MAP of mature green mume fruits during storage at ambient temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.1
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• pp.1-4
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• 2012

O- and Zn-polar ZnO films were grown by DC magnetron sputtering. Growth of high-quality, single-crystal ZnO thin films were confirmed by XRD and pole figure analysis. O-polar ZnO was grown on an $Al_2O_3$ substrate, which was confirmed by a slow growth rate (378 nm/hr), a fast etching rate (59 nm/min), and by the hillocks on the surface after etching. Zn-polar ZnO was grown on a GaN/$Al_2O_3$ substrate, which was confirmed by a fast growth rate (550 nm/hr), a slow etching rate (28 nm/min), and by pits on the surface after etching. Results from the present study show that it is possible to use DC-sputtering to grow ZnO film with the same polarity as other epitaxial growth methods.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.342-349
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• 2009

This study investigated the growth characteristics of carbon nanotubes (CNTs) by changing a period of annealing time and a $C_{2}H_{2}/H_2$ flow ratio at temperature as low as $450^{\circ}C$ with inductively coupled plasma chemical vapor deposition. The 1-nm-thick Fe-Ni-Co alloy thin film served as a catalyst layer for the growth of CNTs, which was thermally evaporated on the 15-nm-thick Al underlayer deposited on the 50-nm-thick Ti diffusion barrier. The annealing at low temperature of $450^{\circ}C$ brought about almost no granulation of the catalyst layer, and the CNT growth was not affected by a period of annealing time. A study of changing the flow rate of $C_{2}H_{2}$ and $H_2$ showed that as the ratio of the $C_{2}H_{2}$ flow rate to the $H_2$ flow rate was lowered, the CNTs were grown to be longer With further decreasing the flow ratio, the length of CNTs reached the maximum and then became shorter. Under the optimized gas flow rates, we successfully synthesized CNTs with a uniform length over a 4-inch Si wafer at $450^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.98-103
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• 2013

The alumina substrates that Ni electrode was printed on and the multi-layered PTCR thermistors of which composition is $(Ba_{0.998}Ce_{0.002})TiO_3+0.001MnCO_3+0.05BN$ were fabricated by a thick film process, and the effect of re-oxidation temperature on their resistivities and resistance jumps were investigated, respectively. Ni electroded alumina substrate and the multi-layered PTC thermistor were sintered at $1150^{\circ}C$ for 2 h under $PO_2=10^{-6}$ Pa and then re-oxidized at $600{\sim}850^{\circ}C$ for 20 min. With increasing the re-oxidation temperature, the room temperature resistivity increased and the resistance jump ($LogR_{290}/R_{25}$) decreased, which seems to be related to the oxidation of Ni electrode. The small sized chip PTC thermistor such as 2012 and 3216 exhibits a nonlinear and rectifying behavior in I-V curve but the large sized chip PTC thermistor such as 4532 and 6532 shows a linear and ohmic behavior. Also, the small sized chip PTC thermistor such as 2012 and 3216 is more dependent on the re-oxidation temperature and easy to be oxidized in comparison with the large sized chip PTC thermistor such as 4532 and 6532. So, the re-oxidation conditions of chip PTC thermistor may be determined by considering the chip size.