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The array growth of ferroelectric nanotubes in anodic porous alumina nanoholes on silicon
이전국,Hyung-Seob Min,Seung-Won Jung 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.3
A highly self-ordered hexagonal array of cylindrical pores has been fabricated by anodizing a thin film of Al on Si substrate and subsequent growth of PbZrTiO3(PZT) in these nanoholes has been performed sol-gel solution infiltration method. The diameter and the aspect ratio of vertically aligned AAO nanopores are about 40 nm and 9:1, respectively. The ferroelectric properties of PZT nanotubes were observed by an electrostatic force microscope (EFM). These nanotubes should provide promising materials for fundamental investigations on nanoscale ferroelectricity, and be useful in ferroelectric nanostorage media. A highly self-ordered hexagonal array of cylindrical pores has been fabricated by anodizing a thin film of Al on Si substrate and subsequent growth of PbZrTiO3(PZT) in these nanoholes has been performed sol-gel solution infiltration method. The diameter and the aspect ratio of vertically aligned AAO nanopores are about 40 nm and 9:1, respectively. The ferroelectric properties of PZT nanotubes were observed by an electrostatic force microscope (EFM). These nanotubes should provide promising materials for fundamental investigations on nanoscale ferroelectricity, and be useful in ferroelectric nanostorage media.
졸겔 스핀 코팅에서 질산촉매가 티탄산연 박막의 물성에 미치는 영향
이전국,정형진,김종희 한국세라믹학회 1991 한국세라믹학회지 Vol.28 No.11
High quality lead titanate thin films were fabricated by spin coating on a silicon substrate. The resulting dried gel layers were uniform in thickness through 2$\times$2 $\textrm{cm}^2$ area, and polycrystalline perovskite structures developed almost crack free with a heat treatment above 50$0^{\circ}C$ in films with thickness above 360 nm. Metastable pyrochlore structures were observed in films with thickness of 160 nm when heat treated at 500 and $600^{\circ}C$, but these structure did not appear in films with thickness of 360 nm. The thickness dependence in crystal structure of films was studied. by varying the substrate condition and analyzing the interface between the film and substrate. In native oxide films on silicon stbstrates, amorphous dried gel layers were heterogeneously nucleated. Metastable cubic pyrochlore structure could be crystallized in amorphous native oxide.
이전국,김종희 한국세라믹학회 1985 한국세라믹학회지 Vol.22 No.1
Experiments related to nitriding silicon with addition of $Si_3N_4$ have provided information on the effects of such inclusion on the phase relationships of Reaction Bonded Silicon Nitride. In the current work specimens containing 0-25wt% Si3N4 which have 55.5wt% $\alpha$ 4.5wt% $eta$, 40wt% amorphous phase were nitrided for 7-20 hours at 1300-135$0^{\circ}C$ The evaluation of nitridation was per-formed by means of $\alpha$-and $\beta$-phase contents determination in nitrided specimens, In order to observe nitrided region between silicon and silicon nitride scanning electron microscopy was used to study reacted region between silicon and silicon nitride particle. For this purpose semiconductor-grade silicon wafer single crystal was used as a silicon source. The incorporation of small amount of $Si_3N_4$ powder is contributed to enhancing the rate of formation of $\alpha$-phase.
Opto-electronic materials and devices
이전국 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Based on multidisciplinary convergence research, new materials and devices for smart human adaptive interface on green technology coping with future environmental pollution and resource exhaustion as well as, silver technology for aging generation are mainly investigated and developed. In our center, diverse ideas through experiments and quantum chemical methods are studied and achieved to realize the new opto-electronic materials and devices. Soft electronics as a promising candidate for next generation industry, and its related core materials such as semiconductor nano quantum dots(QDs), metal nano wire/rod, nanocarbons (graphene etc.), polymer hybrid as well as flexible opto-electronic devices, nanophotonics, and printing process are being investigated. We also improve the performance of optical devices such as laser diodes and LEDs as well as to develop new functional devices such as single photon sources by using semiconductor quantum dots, quantum wells, nanowires or photonic crystals. We grow the semiconductor-based epi-structures and nanomaterials: Quantum dots, Quantum wells, Nanoparticles, Nanowires, etc. In our research center, 2-dimensional (2-D) nanomaterials such as graphene and black phosphorus are explored and synthesized. Especially, passively mode-locked fiber lasers for the femtosecond duration of the laser output are realized based on the 2-D nanomaterials that display high optical nonlinearity. (J.A.Im, W.K.Choi, Y.W.Song, ACS Nano, 8 2014 p11753). Organic solar cell with Ag nanowire electrodes and PTB7:PC70BM active layer shows the Jsc of 20 mA/cm<sup>2</sup> resulting in the PCE of 7.99 %. (B.Wang, D.K.Hwang, Y.J.Oh, Small 20140261, 2014.) Counter-clockwise bipolar resistance switching memory current-voltage (I-V) characteristics are observed within the switching voltage window of 22.5 to 11.9 V with good endurance and retention properties. (J.K.Lee, H.Im, Sci. Rep. DOI 10.1038/srep07354, 2014) MBE Growth and characterization of noble bulk materials (3-D), 2DEG/2DHG (2-D), nanorods (1-D), and quantum dot/ring (0-D) structures for application to photonic and electronic devices are investigated. (S.H.Kim, J.D.Song, W.J.Choi, Electon. Lett. 53(23) 2014 p1731.)
Morphotropic Phase Boundary 영역의 Pb(Zr, Ti)O3-Pb(Co, Nb)O3계 고용체의 격자변형에 따른 강유전 특성 변화
이전국,정형진 한국세라믹학회 1988 한국세라믹학회지 Vol.25 No.6
Pb(Zr, Ti)O3-Pb(Co, Nb)O3 systems were investigated by x-ray diffraction method. System contains rhombohedral, tetragonal, and pseudocubic structures at room temperature. Crystal symmetry was changed from 4-fold symmetry to 3-fold symmetry by substituting Pb(Co1/3, Nb2/3)O3 ; PCN, to Pb(Zr0.52, Ti0.48)O3 ; PZT. As the substituted PCN concentration was increased, an increase in a-axis direction and a decrease in c-axis in the perovskite structure were occurred simultaneously, so that the crystal symmetry was changed into such way. In the higher sinteringtemperatures, the unit cell distortions occurred rather in the lower substitution range of PCN. The ferroelectric properties were maximized at the region that tetragonal and rhombohedral or pseudocubic structures were coexist.