• Journal of Sensor Science and Technology
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• v.28 no.5
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• pp.329-333
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• 2019

Solution-processed oxide thin-film transistors (TFTs) have garnered great attention, owing to their many advantages, such as low-cost, large area available for fabrication, mechanical flexibility, and optical transparency. Negative bias stress (NBS)-induced instability of sol-gel IGZO TFTs is one of the biggest concerns arising in practical applications. Thus, understanding the bias stress effect on the electrical properties of sol-gel IGZO TFTs and proposing an effective recovery method for negative bias stressed TFTs is required. In this study, we investigated the variation of transfer characteristics and the corresponding electrical parameters of sol-gel IGZO TFTs caused by NBS and positive bias recovery (PBR). Furthermore, we proposed an effective PBR method for the recovery of negative bias stressed sol-gel IGZO TFTs. The threshold voltage and field-effect mobility were affected by NBS and PBR, while current on/off ratio and sub-threshold swing were not significantly affected. The transfer characteristic of negative bias stressed IGZO TFTs increased in the positive direction after applying PBR with a negative drain voltage, compared to PBR with a positive drain voltage or a drain voltage of 0 V. These results are expected to contribute to the reduction of recovery time of negative bias stressed sol-gel IGZO TFTs.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.798-800
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• 1998

(Ba,Sr)$TiO_3$ thin films were etched with $Cl_2$/Ar gas mixing ratio in an inductively coupled plasma (ICP) by varying the etching parameter such as f power, do bias voltage, and chamber pressure. The etch rate was $560{\AA}/min$ under Cl_2/(Cl_2+Ar)$ gas mixing ratio of 0.2, rf power of 600 W, do bias voltage of 250 V, and chamber pressure of 5 mTorr, At this time, the selectivity of BST to Pt, $SiO_2$ was respectively 0.52, 0.43. The surface reaction of the etched (Ba,Sr)$TiO_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS).

• Journal of the Semiconductor & Display Technology
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• v.4 no.2 s.11
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• pp.11-14
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• 2005

In plasma processing reactors, it is common practice to control plasma density and ion bombardment energy by manipulating excitation voltage and frequency. In this paper, a dually excited capacitively coupled rf plasma reactor is self-consistently simulated with a three moment model. Effects of phase differences between primary and secondary voltage waves, simultaneously modulated at various combinations of commensurate frequencies, on plasma properties are investigated. The simulation results show that plasma potential and density as well as primary self-dc bias are nearly unaffected by the phase lag between the primary and the secondary voltage waves. The results also show that, with the secondary frequency substantially lower than the primary frequency, secondary self·do bias remains constant regardless of the phase lag. As the secondary frequency approaches to the primary frequency, however, the secondary self-dc bias becomes greatly altered by the phase lag, and so does the ion bombardment energy at the secondary electrode. These results demonstrate that ion bombardment energy can be more carefully controlled through plasma simulation.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.235-239
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• 2002

In this study mesh-type PECVD system was suggested to minimize the hydrogen concentration. The main structural difference between the triode system and a conventional system is that, a third electrode, a mesh, is inserted between the powered and the ground electrode. We investigated several conditions to compare with conventional PECVD. The main effect of mesh was to minimize the substrate damage by ion bombardment and to enhance the surface reaction to induce hydrogen desorption. It was also found that hydrogen concentration decreased but deposition rate increased as increasing applied bias. Applied DC-bia s enhanced sputtering process. Intense ion bombardment causes the weakly bonded hydrogen or hydrogen-containing species to leave the growing film and increased adatom mobility. Furthermore, addition of hydrogen gas enhance the surface diffusion of adatom.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2032-2034
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• 2000

The performance of ac plasma display panels (PDP) is influenced strongly by the surface glow discharge characteristics on the MgO thin films. This paper deals with the surface slew discharge characteristics and some physical properties of MgO thin films prepared by reactive RF planar unbalanced magnetron sputtering in connection with ac PDP. The samples prepared with the do bias voltage of -10V showed lower discharge voltage and lower erosion rate by ion bombardment than those samples prepared by conventional magnetron sputtering or E-beam evaporation. The main factor that improves the discharge characteristics by bias voltage is considered to be due to the morphology changes or crystal structure of the MgO thin film by ion bombardment during deposition process.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.933-936
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• 2000

N-channel poly-Si TFT, processed by Solid Phase Crystalline(SPC) on a glass substrate, has been investigated by measuring its electrical properties before and after stressing. It is observed that the threshold voltage shift due to electrical stress varies with various stress conditions. Threshold voltages measured in 1.5um and 3um poly-Si TFT’s are 3.3V, 37V respectively. With the threshold voltage shift, the degradation of transconductance and subthreshold swing is also observed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.1
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• pp.80-84
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• 2008

We systematically investigated the resistive switching properties of thin $TiO_2$ films on Pt/Ti/$SiO_2$/Si substrates that were embedded with a Co ultra thin layer. An in-situ sputtering technique was used to grow both films without breaking the chamber vacuum. A stable bipolar switching in the current-voltage curve was clearly observed in $TiO_2$ films with an embedded Co ultra thin layer, addressing the high and low resistive state under a bias voltage sweep. We propose that the underlying origin involved in the bipolar switching may be attributed to the interface redox reaction between the Co and $TiO_2$ layers. The improved reproducible switching properties of our novel structures under forward and reverse bias stresses demonstrated the possibility of future non-volatile memory elements in a simple capacitive-like structure.

• Journal of the Korean Magnetics Society
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• v.14 no.4
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• pp.127-130
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• 2004

Magnetic properties and thermal stability by exchange biased perpendicular magnetic anisotropy in (Pd/Co)$_{N}$FeMn multilayer deposited by do magnetron sputtering system are investigated. We measured the perpendicular magnetization curves of (Pd(0.8nm)/Co(0.8nm)$_{5}$FeMn multilayer as function of FeMn thickness and annealing temperature. As FeMn thickness increases from 0 to 21nm, the perpendicular exchange bias(Hex) obtained 127 Oe at FeMn thickness 15nm. As the annealing temperature increases to 24$0^{\circ}C$, the E$_{ex}$ increased from 115 Oe to 190 Oe and disappeared exchange biased perpendicular magnetic anisotropy effect at 33$0^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.627-627
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• 2013

Recently, most studies concerning inorganic CdSe/ZnS quantum dot (QD)-polymer hybrid LEDs have been concentrated on the structure with multiple layers [1,2]. The QD LEDs used almost CdSe materials for color reproduction such as blue, green and red from the light source until current. However, since Cd is one of six substances banned by the Restriction on Hazardous Substances (RoHS) directive and classified into a hazardous substance for utilization and commercialization as well as for use in life, it was reported that the use of CdSe is not suitable to fabricate a photoelectronic device. In this work, we demonstrate a novel, simple and facile technique for the synthesis of ZnO-graphene quasi-core.shell quantum dots utilizing graphene nanodot in order to overcome Cd material including RoHS materials. Also, We investigate the optical and structural properties of the quantum dots using a number of techniques. In result, At the applied bias 10 V, the device produced bluish-white color of the maximum brightness 1118 cd/$m^2$ with CIE coordinates (0.31, 0.26) at the bias 10 V.

• Progress in Superconductivity
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• v.5 no.1
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• pp.5-8
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• 2003

We studied the effect of spin injection on tunneling conduction properties of intrinsic Josephson junctions formed in $Bi_2$$Sr_2$$CaCu_2$$O_{ 8＋x}$ single crystals. properties of an identical stack (10${\times}$5.0${\times}$0.030 $\mu\textrm{m}^3$) of intrinsic Josephson junctions were compared for the bias current injected through Au and Co electrodes. The suppression of the superconducting gap in the $_2$ double layers and the interlayer Josephson critical current was manifested in the tunneling current-voltage characteristics of the stacks. This effect appears to be caused by the pair breaking associated with spin-polarized carriers injected from the Co electrode into the $Bi_2$$Sr_2$$_2$O$CaCu_{ 8＋x}$ single crystal. This study may provide valuable information on clarifying the mechanism of high- $T_{c}$ superconductivity.y.y.