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Synthesis of Pb precursors for PZT films
김욱현,이정규,구상만 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1
Lead zirconate titanate, known as PZT, was discovered in the late 1950’s is used as a piezoelectric material. There are many piezoelectric materials, but in the aspect of permittivity, electromechanical coupling coefficient, and pyroelectrical response, PZT shows high performance. PZT thin films are fabricated by sol-gel, MOCVD and so on. Among these methods, MOCVD seems to be the best process because other methods have drawbacks in achieving constant ratio, limitation of mass production, and purity problem. General MOCVD precursors are Phthd<sub>2</sub>, Zr(OPr)<sub>4</sub>, and Ti(OiPr)<sub>4</sub>, but Pbthd<sub>2</sub> has low vapor pressure, and bad decomposition behavior compared with Ti and Zr precursors. Therefore we synthesized Pb<sup>2+</sup> and Pb<sup>4+</sup> precursors. In case of Pb<sup>2+</sup>, precursor which used aminoalcohol ligand showed good vapor pressure, so we modified aminoalcohol ligand to synthesis better precursor in viewpoint of volatility. Next in Pb<sup>4+</sup>, precursors were synthesized by coordinating ligands with two phenyl ligands as stabilizer. Pb precursors were defined by IR, NMR, TGA, X-ray crystallography, and thermal decomposition and spin coating with sol-gel mixed with Ti, Zr precursors verified PZT.
김욱현,우제욱,전주영,Kim, Ukhyun,Woo, Jewook,Jeon, Jooyoung 한국전기전자학회 2022 전기전자학회논문지 Vol.26 No.3
In this paper, a two-stage single-ended power amplifier (PA) with broadband gain characteristics was presented by utilizing a radio frequency (RF) transformer (TF), which is essential for a differential amplifier. The bandwidth of a PA can be improved by designing TF to have broadband characteristics and then applying it to the inter-stage matching network (IMN) of a PA. For broadband gain characteristics while maintaining the performance and area of the existing PA, an IMN was implemented on an monolithic microwave integrated circuit (MMIC) and a multi-layer printed circuit board (PCB), and the simulation results were compared. As a result of simulating the PA module designed using InGaP/GaAs HBT model, it has been confirmed that the PA employing the proposed design method has an improved fractional bandwidth of 19.8% at a center frequency of 3.3GHz, while the conventional PA showed that of 11.2%.
김욱현,성시준,우성호 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1
A simple method was developed to tune the work function (WF) of indium tin oxide (ITO) cathode in inverted polymer solar cells (PSCs) by inserting a poly(diallyldimethylammonium chloride) (PDDAC) nanolayer as an electron collecting layer (ECL). The WF of ITO is dramatically reduced by dipole formation between the cationic amine of the PDDAC and the anionic oxygen of ITO. A reduction of ITO WF leads to improved electron selectivity. As a result, all solar cell parameters including short circuit current density, open circuit voltage and fill factor are improved, leading to the power conversion efficiency of 2.64% for P3HT:PC71BM active systems under AM1.5G illumination, which is significantly higher than that of the control inverted PSC with blank ITO and comparable to that of the control inverted PSC with ZnO ECL. The results provide an efficient method for interface engineering in organic-based optoelectronic devices.
Synthesis of titanium precursors for titania nanoparticles
김욱현,구상만,이정규 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Titania nanoparticles widely used in cosmetics, high refractive index pigments, photocatalysts, semiconductors and other industrial areas. However the instabilities of typical titanium precursor, such as TiCl4 and Ti(OR)4, cause rapid hydrolysis and condensation in aqueous solution, therefore resulting irregular size and morphology of prepared titania nanoparticles. In this presentation, various titanium precursors which are stable in aqueous solution were synthesized with the reaction of TiCl4 or Ti(OR)4 and ligands, and titania nanoparticles were prepared using the titanium precursors. The resulting titanium precursors and nanoparticles were characterized by spectroscopic analysis.