• Journal of the Korean Vacuum Society
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• v.15 no.6
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• pp.624-629
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• 2006

The energy transfer process between GaN and Nd ions as well as Mg codoping effect were investigated in Nd-implanted GaN films. Photoluminescence (PL) and PL excitation spectroscopies were performed on $^4F_{3/2}{\rightarrow}^4I_{9/2}$ Nd ionic level transition. At least three below bandgap traps were identified in the energy transfer process. The number of one particular trap, which is assigned to be an isoelectronic Nd trap, is increased with the Mg-codoping. The emission efficiency with above gap excitation, which emulates the electrical excitation, is further increased in GaN:Mg,Nd.

• Advances in environmental research
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• v.5 no.1
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• pp.61-77
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• 2016

$NanoTiO_2$ was synthesized by ultrasonication assisted sol-gel process and subjected to iron doping and carbon-iron codoping. The synthesized catalysts were characterized by XRD, HR-SEM, EDX, UV-Vis absorption spectroscopy and BET specific surface area analysis. The average crystallite size of pure $TiO_2$ was in the range of 30 - 33 nm, and that of Fe-$TiO_2$ and C-Fe $TiO_2$ was in the range of 7 - 13 nm respectively. The specific surface area of the iron doped and carbon-iron codoped nanoparticles was around $105m^2/g$ and $91m^2/g$ respectively. The coupled semiconductor photo-Fenton's activity of the synthesized catalysts was evaluated by the degradation of a cationic dye (C.I. Basic blue 9) and an anionic dye (C.I. Acid orange 52) with concurrent investigation on the operating variables such as pH, catalyst dosage, oxidant concentration and initial pollutant concentration. The most efficient C-Fe codoped catalyst was found to effectively destruct synthetic dyes and potentially treat real textile effluent achieving 93.4% of COD removal under minimal solar intensity (35-40 kiloLUX). This reveals the practical applicability of the process for the treatment of real wastewater in both high and low insolation regimes.

• 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 Chemical Engineering Research
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• v.40 no.6
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• pp.752-756
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• 2002

Green-emitting $Zn_2SiO_4:Mn$ phosphors for PDP(Plasma Display Panel) application were synthesized by colloidal seed-assisted spray pyrolysis process. The codoping with $Gd^{3+}/Li^+$, which replaces $Si^{4+}$ site in the willemite structure, was performed to improve the luminous properties of the $Zn_2SiO_4:Mn$ phosphors. The particles prepared by spray pyrolysis process using fumed silica colloidal solution had a spherical shape, small particle size, narrow size distribution, and non-aggregation characteristics. The $Gd^{3+}/Li^+$ codoping amount affected the luminous characteristics of $Zn_2SiO_4:Mn$ phosphors. The codoping with proper amounts of $Gd^{3+}/Li^+$ improved both the photoluminescence efficiency and decay time of $Zn_2SiO_4:Mn$ phosphor particles. In spray pyrolysis, the post-treatment temperature is another factor controlling the luminous performance of $Zn_2SiO_4:Mn$ phosphors. The $Zn_{1.9}SiO_4:Mn_{0.1}$ phosphor particles containing 0.1 mol% $Gd^{3+}/Li^+$ co-dopant had a 5% higher PL intensity than the commercial product and 5.7 ms decay time after post-treatment at $1,145^{\circ}C$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.101-102
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• 2007

ZnO에 Li과 Al이 codoping된 박막을 magnetron spuuter을 이용하여 사파이어 기판 위에 성장하였다. 성장시킨 박막에 대한 구조적, 전기적, 광학적 특성들을 관찰 하였으며, 증착 분위기 조절에 따라서 에피텍셜한 박막을 얻을 수 있었다. $LiAlO_2$ 도핑농도가 증가함에에 따라 전기적으로는 부도체에 가까운 특성을 나타내면서, 광학 밴드갭 에너지가 증가하는 현상을 관찰할 수 있었다.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.213-218
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• 2004

Be-codoped GaMnAs layers were systematically grown via molecular beam epitaxy with varying Mn- and Be-flux. Mn flux was controlled to cover from solid solution type GaMnAs to precipitated GaMnAs. Two Be flux were chosen to exhibit semiconducting and metallic resistivity in the grown layers. The structural, electrical, and magnetic properties of GaAs:(Mn, Be) were investigated. The lightly Be-codoped GaMnAs layers showed ferromagnetism at room temperature, but did not reveal magnetotransport due to small magneto-resistance and high resistance of the matrix. However, room temperature magnetotransport could be observed in the degenerate Be-codoped GaMnAs layers, and which was assisted by the high conductivity of the matrix. The Be-codoping has promoted segregation of new ferromagnetic phase of MnGa as well as MnAs.

• Journal of the Korean Ceramic Society
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• v.28 no.2
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• pp.101-108
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• 1991

0.2 mo1% La doped BaTiO3 samples were prepared by a wet chemical process (Pechini process) and electrical conductivity were measured from annealing temperatures(800-110$0^{\circ}C$) to room temperature continuously. 2 probe I-V characteristics showed that Pt electrodes were non-ohmic below about 80$0^{\circ}C$ for Ladoped sample. I-V curves showed varistor behavior and breakdown voltages showed PTC-like behavior. AC complex impedance of 0.2 La and 0.05 Mn mo1% doped BaTiO3 samples with three different electrodes (electroless Ni, Pt, Ag electrodes) were measured with temperature variation. Complex impedance plots showed that the samples with electroless Ni electrodes have negligible electrode resistance. Samples with Ag or Pt paste electrodes showed large electrode resistance. PTC effect, which is defined as the ratio of maximum resistance to minimum resistance, was found to be less than 10 for 0.2 mo1% La doped dense sample however greater than 105 with codoping of 0.05 mo1% Mn and 0.2 mol% La.

• Advances in nano research
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• v.4 no.3
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• pp.157-165
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• 2016

The photocatalytic (PC) activity of anatase titania nanoparticles can be improved through codoping with transition metals and nitrogen. In addition, the PC activity can also be improved by creating monodisperse, mesoporous nanoparticles of titania. The question naturally arose as to whether combining these two characteristics would result in further improvement in the PC activity or not. Herein, we describe the synthesis and photocatalytic characteristics of codoped, monodisperse anatase titania. The transition metals tested in the polydisperse and the monodisperse forms were Mn, Co, Ni, and Cu. In each case, it was found that the monodisperse version had a higher PC activity compared to the corresponding polydisperse version.

• Journal of Electrochemical Science and Technology
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• v.8 no.4
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• pp.338-343
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• 2017

Activated carbon has lower electrical conductivity and reliability than other carbonaceous materials because of the oxygen functional groups that form during the activation process. This problem can be overcome by doping the material with heteroatoms to reduce the number of oxygen functional groups. In the present study, N, F co-doped activated carbon (AC-NF) was successfully prepared by a microwave-assisted hydrothermal method, utilizing commercial activated carbon (AC-R) as the precursor and ammonium tetrafluoroborate as the single source for the co-doping of N and F. AC-NF showed improved electrical conductivity ($3.8\;S\;cm^{-1}$) with N and F contents of 0.6 and 0.1 at%, respectively. The introduction of N and F improved the performance of the pertinent supercapacitor: AC-NF exhibited an improved rate capability at current densities of $0.5-50mA\;cm^{-2}$. The rate capability was higher compared to that of raw activated carbon because N and F codoping increased the electrical conductivity of AC-NF. The developed method for the co-doping of N and F using a single source is cost-effective and yields AC-NF with excellent electrochemical properties; thus, it has promising applications in the commercialization of energy storage devices.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.826-833
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• 2004

In this study, photosensitivity dynamics in SiO$_2$ glass with the composition similar to that of silica Planar Lightwave Circuit (PLC) devices was investigated as a fundamental study prior to the device fabrication. Silica bulk glasses with similar composition to the core layer of PLC devices were prepared with variable composition of B$_2$O$_3$. The photosensitivity in boron and germanium co-doped SiO$_2$ glass yields refractive index change $\Delta$n as high as 10$\^$-3/. However such index modulation disappeared after annealing. From the result of annealing experiment and W absorption / Raman spectra, we conclude the compaction model is applicable to our glass system.