• Macromolecular Research
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• v.12 no.1
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• pp.22-25
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• 2004

We have synthesized aniline oligomer composites by using heteropoly acid (H$_4$SiW$_{12}$O$_{40}$ ) as a dopant. The doping and dedoping processes of the aniline oligomer composites were investigated with the aid of UV- Vis spectra. The bands of the aniline oligomer at 572 nm weakened or disappeared, and the bands at 268, 412, and 771 nm appeared, after the aniline oligomer was doped. When the solution of the aniline oligomer doped with H$_4$SiW$_{12}$O$_{40}$ was kept at lower values of pH, the aniline oligomer could not be dedoped by dilution. The turning point of doping and dedoping occurred at pH 5.5. The band at 771 nm shifted towards longer wavelengths when the aniline oligomer composites were synthesized using acetone as the solvent. This observation indicates that the molecular chain became stretched. In addition, we also investigated the change of the electronic absorption spectra of the composites with respect to the time laid up.id up.

• Journal of the Korean Chemical Society
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• v.63 no.2
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• pp.94-101
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• 2019

Nb, Mo-doped and Nb/Mo-codoped $VO_2(M)$ nanocrystallites with various doping levels were synthesized for the first time by a hydrothermal and post thermal transformation method. The reversible phase transition characteristics of those doped $VO_2(M)$ was comparatively investigated. Nb-doping of $VO_2(M)$ by this method resulted in a very efficient lowering of the transition temperature ($T_c$) with a rate of $-16.7^{\circ}C/at.%$ that is comparable to W-doping, while Mo-doping did not give a serious reduction of $T_c$ with only a rate of $-5.1^{\circ}C/at.%$. Nb/Mo-codoping gave a similar result to Nb-doping without a noticeable difference. The thin films of Nb-doped and Nb/Mo-codoped $VO_2(M)$ with a thickness of ca. 120 nm were prepared by a wet-coating of the nanoparticle-dispersed solutions. Those films showed a good thermochromic modulation of near infrared radiation with 30-35% for Nb-doped $VO_2(M)$ and 37-40% for Nb/Mo-codoped ones. Nb/Mo-codoped $VO_2(M)$ film showed slightly enhanced thermochromic performance compared with Nb-doped $VO_2(M)$ film.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.846-849
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• 2003

Doping effect of various ions in Bi-layered ferroelectric $SrBi_2$$Nb_2$$O_{9}$ (SBN) ceramics was studied. Undoped SBN ceramic and SBN ceramics doped with $Ba^{2＋}$, $Pb^{2＋}$,$ Ca^{2＋}$ , $Bi^{3＋}$ , $La^{3＋}$ , $Ti^{4＋}$ , $Mo^{6＋}$ , and $W^{6＋}$ ions were made by a solid state reaction. Dielectric constants were measured with temperature. Ferroelectric transition temperature decreased with $Pb^{2＋}$ , $Ba^{2＋}$ , $La^{3＋}$ doping, but the transition temperature increased with $Ca^{2＋}$ , $Bi^{3＋}$ , $Ti^{4＋}$, $Mo^{6＋}$ , or$ W^{6＋}$ ionic doping. These results show that the ion size plays an important role in the ferroelectricity of SBN ceramic.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.304-308
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• 2000

WO$_3$/SnO$_2$ceramics has been suggested as an effective sensing material for monitoring offensive odor or pollutant gases. This work was focussed on improving long-term stability, which has been a principal problem generally taking place in SnO$_2$semiconductor gas sensor. Miniaturized thick film gas sensors were fabricated by screen printing technique. Two types of sensor materials, W doped SnO$_2$and WO$_3$mixed SnO$_2$, were comparatively investigated on those long-term stability and sensitivites to several gases. Small amount of W doping(0.1 mol%) into SnO$_2$largely improved the long-term stability. The W(0.1 mol%) doped SnO$_2$gas sensor had higher sensitivities to both acetone and alcohol compared with WO$_3$(5 wt%) mixed SnO$_2$gas sensor. On the contrary, WO$_3$(5 wt%) mixed SnO$_2$gas sensor showed more superior sensitivity to cigarette smoke due to larger W content.

• Progress in Superconductivity
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• v.4 no.1
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• pp.10-13
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• 2002

We report the effect of Ca doping in $YBa_2Cu_3O_{7-\delta}$ (YBCO) thin films grown on the Rolling- Assisted, Biaxially Textured Substrates (RABiTS) with the architecture of $CeO_2/YSZ/CeO_2/Ni$. Critical currents of bilayer and trilayer structures of $YBCO/Y_{0.7}Ca_{0.3}Ba_2Cu_3O_{7-\delta}$/(YCaBCO) as well as undoped YBCO for comparison have been measured in a wide range of temperatures and fields. For $6-8^{\circ}$ grain boundaries, 30% Ca-doping in bilayer structure enhances $J_c$ as high as 35%. The enhancement is larger at low temperatures and at magnetic fields. On the other hand, 30% Ca-doping in trilayer structure reduces $J_c$ as high as 60%. Combined with slightly lower $T_c$, this indicates that Ca is overdoped in this structure and degrades GBs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.285-290
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• 2015

The phase change memory material is an active element in phase change memory and exhibits reversible phase transition behavior by thermal energy input. The doping of the phase change memory material with Ga leads to the increase of its crystallization temperature and the improvement of its amorphous stability. In this study, we investigated the effect of GaGe sputtering power on the formation of the phase change memory material including Ga. The deposition rate linearly increased to a maximum of 127 nm and the surface roughness remained uniform as the GaGe sputtering power increased in the range from 0 to 75 W. The Ga concentration in the thin film material abruptly increased at the critical sputtering power of 60 W. This influence of GaGe sputtering power was confirmed to result from a combined sputtering-evaporation process of Ga occurring due to the low melting point of Ga ($29.77^{\circ}C$).

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.192-198
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• 2017

In this paper, we propose a novel double gate vertical channel tunneling field effect transistor (DVTFET) with a dielectric sidewall and optimization characteristics. The dielectric sidewall is applied to the gate region to reduced ambipolar voltage ($V_{amb}$) and double gate structure is applied to improve on-current ($I_{ON}$) and subthreshold swing (SS). We discussed the fin width ($W_S$), body doping concentration, sidewall width ($W_{side}$), drain and gate underlap distance ($X_d$), source doping distance ($X_S$) and pocket doping length ($X_P$) of DVTFET. Each of device performance is investigated with various device parameter variations. To maximize device performance, we apply the optimum values obtained in the above discussion of a optimization simulation. The optimum results are steep SS of 32.6 mV/dec, high $I_{ON}$ of $1.2{\times}10^{-3}A/{\mu}m$ and low $V_{amb}$ of -2.0 V.

• Korean Journal of Materials Research
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• v.14 no.5
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• pp.328-333
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• 2004

Transparent ZnO:Al conductor films for the optoelectronic devices were deposited by using the capacitively coupled DC magnetron sputtering method. The effect of Al doping concentration and discharge power on the electrical and optical properties of the films was studied. The film resistivity of $8.5${\times}$10^{-4}$ $\Omega$-cm was obtained at the discharge power of 40 W with the ZnO target doped with 2 wt% $Al_2$$_O3$. The transmittance of the 840 nm thick film was 91.7% in the visible waves. Increasing doping concentration of 3 wt% $Al_2$$O_3$ in ZnO target results in significant decrease of film resistivity, which may be due to the formation of $Al_2$$O_3$ particles in the as-deposited ZnO:Al film and the reduced ZnO grain sizes. Increasing DC power from 40 to 60 W increases deposition rate by more than 50%, but can induce high defect density in the film, resulting in higher film resistivity.

• 한국초전도학회:학술대회논문집
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• v.12
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• pp.4-4
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• 2002

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.451-456
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• 2013

To study emission properties of white phosphorescent organic light emitting devices (PHOLEDs), we fabricated white PHOLEDs of ITO(150 nm) / NPB(30 nm) / TcTa(10 nm) / mCP(7.5 nm) / light-emitting layer(25 nm) / UGH3(5 nm) / Bphen(50 nm) / LiF(0.5 nm) / Al(200 nm) structure. The total thickness of light-emitting layer with co-doping and blue-doping/co-doping using a host-dopant system was 25 nm and the dopant of blue and red was FIrpic and $Bt_2Ir$(acac) in UGH3 as host, respectively. The OLED characteristics were changed with position and thickness of blue doping layer and co-doping layer as light-emitting layer and the best performance seemed in structure of blue-doping(5 nm)/co-doping(20 nm) layer. The white PHOLEDs showed the maximum current density of $34.5mA/cm^2$, maximum brightness of $5,731cd/m^2$, maximum current efficiency of 34.8 cd/A, maximum power efficiency of 21.6 lm/W, maximum quantum efficiency of 15.6%, and a Commission International de L'Eclairage (CIE) coordinate of (0.367, 0.436) at $1,000cd/m^2$.