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Loaded-line Ferroelectric Phase Shifter Based on Mn-doped (Ba,Sr)TiO3 Thin Films for Ka-band Systems
류한철,문승언,이수지 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.7
This paper presents on the microwave properties of a loaded-line ferroelectric phase shifter basedon (Ba, Sr)TiO3 (BST) thin films for Ka-band applications. In order to reduce the dielectric loss ofthe BST thin film and its enhance a dielectric tunability, we optimized the deposition of Mn-doped(Ba0.5, Sr0.5)TiO3 (Mn-BST) thin films on MgO substrates by using pulsed laser deposition (PLD). The crystallinity, microstructure and thickness of the thin films were investigated by using an Xraydiffractometer and a scanning electron microscope, respectively. We designed and fabricated atunable ferroelectric capacitor loaded coplanar waveguide (CPW) type phase shifter to enhance thetuning and the loss characteristics of a conventional CPW ferroelectric phase shifter. The fabricatedloaded-line phase shifter showed a low return loss of −15 dB in the frequency band from 25 GHzto 35 GHz. The differential phase shift was 293◦, and the insertion loss decreased from −11.3 dBto −1.4 dB with increasing dc bias voltage from 0 to 80 V at 35 GHz.
A Novel DPP Based Polymer HTL for PbS CQD-SCs
천형진,김홍일,백세웅,류승언,이승진,최민재,최경원,Margherita Biondi,Sjoerd Hoogland,F. Pelayo Garcia de Arquer,권순기,박태호,Edward H. Sargent,김윤희 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
DPP-based polymers are widely used in organic photovoltaics (OPV) and organic field-effect transistors (OFET) as the p-type materials. DPP with bithiophene (π-bridge) has already been proven to have excellent charge transport properties owing to an attractive S···O electrostatic interaction that induces π–π stacking. Therefore, we were performed Stille coupling reaction to combine these D–A building blocks to form the desired HTL. PD2FCT-29DPP (D1–A1–D1–A2) is a D–A alternating copolymer from the DPP (A2) and CPDT (D1) with fluorinated BT (A1). PD2FCT-29DPP-based devices achieve an FF of 70.0% and a PCE of 14.0%.
김산해,최유라,조윤정,류승언,강상욱 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.8
Water-channels were generated into cellulose acetate (CA) via the addition of polyethylene glycol (PEG) and water-assisted pressures. It was found that the PEG used as the plasticizer could enable pores in CA to be controlled. Since the PEG had a relatively small molecular weight, it easily penetrated into polymer chains and formed abundant free volumes in the CA, enabling the pore control. In addition, the PEG enhanced the thermal stability of CA by forming new bipolar interactions and hydrogen bonding between the CA chains and the hydroxyl groups of PEG. From these results, it could be expected that due to the low cost and eco-friendliness of PEG and CA, they could be widely used to manufacture separators used in batteries.