• Journal of the Korean Chemical Society
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• v.61 no.2
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• pp.57-64
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• 2017

Monoclinic $VO_2(M)$ nanoparticles codoped with 1.5 at. % W and 2.9 at. % Mg were synthesized by the hydrothermal treatment and post-thermal transformation method of $V_2O_5-H_2C_2O_4-H_2O$ with $Na_2WO_4$ and $Mg(NO_3)_2$. The composite thin film of the W/Mg-codoped $VO_2(M)$ with a commercial acrylic block copolymer was also prepared on PET substrate by wet-coating method. The reversible phase transition characteristics of the codoped $VO_2(M)$ nanoparticles and the composite film were investigated from DSC, resistivity and Vis-NIR transmittance measurements compared with the undoped and Wdoped $VO_2(M)$ samples. Mg-codoping into W-doped $VO_2(M)$ nanoparticles synergistically enhanced the transition characteristics by increasing the sharpness of transition while the transition temperature ($T_c$) lowered by W-doping was maintained. The codoped composite film showed the prominently enhanced NIR switching efficiency compared to only W-doped $VO_2(M)$ film with a lowered $T_c$.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.73-77
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• 2005

Motivated by the enhanced magnetic properties of Mg-codoped GaMnN ferromagnetic semiconductors, Be-codoped GaMnAs films were grown via molecular beam epitaxy with varying Mn flux at a fixed Be flux. The structural, electrical, and magnetic properties were investigated. GaAs:(Mn,Be) films showed metallic behavior while GaAs:Mn films showed semiconducting behavior as determined by the temperature dependent resistivity measurements. The Hall-effect measurements with varying magnetic field showed clear anomalous Hall effect up to room temperature proving ferromagnetism and magnetotransport in the GaAs:(Mn,Be) films. Planar Hall resistance measurement also confirmed the properties. The dramatic enhancement of the Curie temperature in GaMnAs system was attributed to Be codoping in the GaMnAs films as well as MnAs precipitation.