• JSTS:Journal of Semiconductor Technology and Science
• /
• v.8 no.1
• /
• pp.40-45
• /
• 2008

We developed small molecular organic nonvolatile $4F^2$ memory cells using metal layer evaporation followed by $O_2$ plasma oxidation. Our memory cells sandwich an upper ${\alpha}$-NPD layer, Al nanocrystals surrounded by $Al_2O_3$, and a bottom ${\alpha}$-NPD layer between top and bottom electrodes. Their nonvolatile memory characteristics are excellent: the $V_{th},\;V_p$ (program), $V_e$ (erase), memory margin ($I_{on}/I_{off}$), data retention time, and erase and program endurance were 2.6 V, 5.3 V, 8.5 V, ${\approx}1.5{\times}10^2,\;1{\times}10^5s$, and $1{\times}10^3$ cycles, respectively. They also demonstrated symmetrical current versus voltage characteristics and a reversible erase and program process, indicating potential for terabit-level nonvolatile memory.

• Proceedings of the IEEK Conference
• /
• 2003.07b
• /
• pp.1065-1068
• /
• 2003

For the first time, high quality ultra-thin strained Si/SiGe on Insulator (SGOI) substrate with total SGOI thickness( $T_{Si}$ + $T_{SiGe}$) of 13 nm is developed to combine the device benefits of strained silicon and SOI. In the case of 6- 10 nm-thick top silicon, 100-110 % $I_{d,sat}$ and electron mobility increase are shown in long channel nFET devices. However, 20-30% reduction of $I_{d,sat}$ and electron mobility are observed with 3 nm top silicon for the same long channel device. These results clearly show that the FETs operates with higher performance due to the strain enhancement from the insertion of SiGe layer between the top silicon layer and the buried oxide(BOX) layer. The performance degradation of the extremely thin( 3 nm ) top Si device can be attributed to the scattering of the majority carriers at the interfaces.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.683-686
• /
• 2002

The hydrodynamic instability of the three-dimensional boundary-layer over a rotating disk has been numerically investigated for three cases flows using linear stability theory (i.e. Rossby number, Ro = -1, 0, and 1). Detailed numerical values of the disturbance wave number, wave frequency, azimuth angle, radius (Reynolds number, Re) and other characteristics have been calculated for $K{\acute{a}}rm{\acute{a}}n$, Ekman and $B{\"{o}}ewadt$ boundary-layer flows. Neutral curves for these flows are presented. Presented are the neutral stability results concerning the two instability modes (Type I and Type II) by using a two-point boundary value problem code COLUEW that was based upon the adaptive orthogonal collocation method using B-spline. The prediction from the present results on both instability modes among the three cases agrees with the previously known numerical and experimental data well.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.12
• /
• pp.2436-2440
• /
• 2009

In this work, TCO-less dye-sensitized solar cells (DSCs) using Ti-mesh layer is fabricated for high-efficient low-cost solar cell application. The Ti-mesh metal can replace TCO in the photo-electrode part of DSCs, thus the cell structure is composed of a glass/dye sensitized TiO2 particle/ Ti-mesh layer/electrolyte/Pt sputtered counter electrode/ glass. The Ti-mesh electrode with high conductivity can collect electrons from the $TiO_2$ layer and allows the ionic diffusion of $I^-/I_3^-$ through the mesh hole. Thin Ti-mesh ($\sim40{\mu}m$ in thickness) electrode material is processed using rapid prototype method. The efficiency of prepared TCO-less DSCs sample is about 1.45 % ((ff: 0.5, Voc: 0.52V, Jsc: 5.55 $mA/cm^2$).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.2
• /
• pp.196-200
• /
• 2004

Using polyimide Langmuir-Blodgett(LB) films as a tunneling harrier, we fabricated Au/Polyimide/1-layer arachidic acid/Pb structure in order to investigate electron transport properties through a junction. It was found that 9-layer polyimide LB films function as a good tunneling harrier in a study of current-voltage(I-V) chararteristics. And several peaks originating in the vibrational modes of the constituent molecules of 1-layer arachidic acid LB films were clearly observed in d$^2$V/dI$^2$- V corves.

• Journal of Welding and Joining
• /
• v.25 no.4
• /
• pp.65-71
• /
• 2007

Laser weldability of the aluminized steel for the full penetration welding will be described in this paper. We focused on the effect of Al coating conditions on weld strength. For these objectives, aluminized steel sheets that have various thickness and coating weight were prepared for laser welding. And then, tensile-shear and hardness test were carried out. At the same time, Al contents in weld after laser welding were analyzed and their correlations with mechanical properties were investigated. Besides, as removing partially coating layer, weldability has been investigated according to the position of coating layer. As a result of this study, tensile-shear strength was decreased with increasing Al contents in weld, and Al of coating layer caused grain growth.

• Journal of the Korean Magnetics Society
• /
• v.10 no.2
• /
• pp.62-66
• /
• 2000

Annealing cycle number and nonmagnetic layer thickness dependences of interlayer coupling field ( $H_{inf}$ ) and coercivity ( $H_{cf}$ ) of free magnetic layer on NiMn alloy-spin valve films (SVF) were investigated. The SVF is Glass (7059)/N $i_{81}$F $e_{l9}$(70 $\AA$)/Co(10 $\AA$)/Cu(t $\AA$)/Co(15 $\AA$)N $i_{81}$$Fe_{19}$(35 $\AA$)/N $i_{25}$M $n_{75}$(250 $\AA$)Ta(50 $\AA$) films, it were fabricated using the dc sputtering method at different pinning layer thickness and nonmagnetic spacer thickness (Cu thickness; 30 $\AA$, 35 $\AA$, 40 $\AA$) of NiMn alloy with 25 at.%. Ni In case that Cu thickness of SVF is 35 $\AA$ and peak exchange coupling field ( $H_{ex}$) was 620 Oe, while coercivity $H_{c}$ = 280 Oe and MR ratio showed 2.5%. As for $H_{inf}$ and $H_{cf}$ , every SVF increased up to the stabilized values with the increase of annealing cycle number 15, which were $H_{inf}$ of 120 Oe and $H_{cf}$ of 75 Oe. The increase of $H_{cf}$ with the annealing cycle number seems to be caused by the effective reduction of Cu layer thickness due to the increase of interfacial mixing of Cu layer and Co layer. In addition, the $H_{inf}$ and $H_{cf}$ dependences of free NiFe layer by the interfacial mixing effect were appeared the different aspects when Cu layer becomes more thinner and thicker than Cu layer thickness of 35 $\AA$, respectively.ively....

• Journal of Korea Multimedia Society
• /
• v.13 no.9
• /
• pp.1299-1313
• /
• 2010

Top-k queries return k objects that users most want in the database. The Partitioned-Layer Index (simply, the PL -index) is a representative method for processing the top-k queries efficiently. The PL-index partitions the database into a number of smaller databases, and then, for each partitioned database, constructs a list of sublayers over the partitioned database. Here, the $i^{th}$ sublayer in the partitioned database has the objects that can be the top-i object in the partitioned one. To retrieve top k results, the PL-index merges the sublayer lists depending on the user's query. The PL-index has the advantage of reading a very small number of objects from the database when processing the queries. However, since many random accesses occur in merging the sublayer lists, query performance of the PL-index is not good in environments like disk-based databases. In this paper, we propose the Abstracted Partitioned-Layer Index (simply, the APL-index) that significantly improves the query performance of the PL-index in disk-based environments by reducing the number of random accesses. First, by abstracting each sublayer of the PL -index into a virtual (point) object, we transform the lists of sublayers into those of virtual objects (ie., the APL-index). Then, we virtually process the given query by using the APL-index and, accordingly, predict sublayers that are to be read when actually processing the query. Next, we read the sublayers predicted from each sublayer list at a time. Accordingly, we reduce the number of random accesses that occur in the PL-index. Experimental results using synthetic and real data sets show that our APL-index proposed can significantly reduce the number of random accesses occurring in the PL-index.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.412-414
• /
• 2003

This paper is about research of scintillator layer, which is used for Hybrid method to increase electric signals in a-Se, the material of Direct method. In case of the thermal evaporation, CsI has column structure which is an disadvantage as scintillator. But it decreases scattering of incident X-ray, has better Light output intensity than other scintillation materials. CsI was made by Thermal evaporation. The Doping material, Na, 0.1, 0.3, 0.5, 0.7g were added in each sample. Analysis of absorbed wavelength, PL(Photoluminescence), Light output intensity, SEM, and XRD analysis were performed to analyze optical characteristics. Doping rate of CsI:Na to use as scintillation layer in a-Se based detector could be optimized.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.415-417
• /
• 2003

CsI 형광체는 X선에 대한 분해능 및 변환효율이 우수한 물질이다. 최근 대면적 평판형 X선 영상검출기의 변환층으로 이용하기 위해 CsI 형광체의 대면적 제조에 대한 연구가 활발히 진행되고 있다. 본 논문은 진공 열증착법을 이용하여 증착속도(3, 3.8, $4.5\;{\mu}m/min$)에 따라 $20\;{\mu}m$ 두께의 CsI 필름을 제조하였고, XRD 및 SEM 분석을 통해 CsI 필름의 기하학적 구조를 조사하였다. 증착된 CsI 필름은 증착속도에 관계없이 복잡한 다결정 구조를 가지며, $3\;{\mu}m/min$의 증착속도에서 약 $1\;{\mu}m$ 크기로 needle-like 한 columnar structure를 가졌다. As results, about 3um/min evaporation rate formed as good geometry characteristics CsI layer.