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Strain Dependence of the Electronic Properties of LaTiO3 Thin Films
문순재,Y. S. Kim 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.10
We report on the transport and the core-level X-ray photoemission spectroscopy data of fullystrainedLaTiO3 thin films grown on GdScO3 and SrTiO3 substrates. We observed that LaTiO3thin film grown on GdScO3 showed insulating behavior but that grown on SrTiO3 exhibited ametallic character. We found that while the La 4d photoemission spectra of the two films werenearly the same, their Ti 2p and O 1s data revealed a difference. Our results suggest that straininducedchanges in the Ti-O bonding play an important role in the electronic properties of LaTiO3thin films.
Temperature Dependence of the Optical Response of Perovskite-type SrIrO3 Thin Film
문순재 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.8
We report on the temperature-dependent optical absorption spectra of an orthorhombic SrIrO3thin film in the energy region between 0.08 and 6 eV. The optical absorption spectra show thecharacteristic spectral features associated with spin-orbit coupling-induced effective total angularmomentum Jeff states. A Drude-like response from the electrons in the Jeff = 1/2 bands isobserved in the energy region below about 0.5 eV followed by an interband transition from the Jeff= 3/2 to the Jeff = 1/2 bands at 0.7 eV. The electron excitations between the Jeff bands exhibita strong temperature dependence that is different from the behavior of conventional metals. Thespectral weight analysis of the absorption data suggests an anomalous low-frequency electrodynamicbehavior for of SrIrO3.
PLD Growth of Epitaxially-stabilized 5d Perovskite SrIrO3 Thin Films
장승엽,문순재,전병철,정진석 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.6
We have investigated the details of the growth behavior of epitaxially-stabilized 5d perovskite SrIrO3 thin films deposited by using a pulsed laser deposition method. During the deposition,a marked decrease in plume size was observed, which was accompanied by the formation of Irrich conical structures on the surface of the polycrystalline SrIrO3 target. High-resolution X-ray diffraction studies revealed that films thicker than certain thickness exhibited a mixed character of a high-quality phase and a relatively poor-quality phase while thinner films showed a high crystalline quality. These observations offer valuable information on the correlation between the plume status and the crystalline quality of iridate thin films.
최우석,문순재,B. C. Jeon,J. H. Lee,이윤상 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
We investigated the optical response of multiferroic hexagonal TbMnO3 thin films at various temperatures. We observed an anomalous temperature dependence of the lowest lying inter-site transition peak, which is in good accord with that of the exchange interaction. Our finding is strongly suggestive of strong charge-spin coupling in this multiferroic compound.
양상모,문순재,김태헌,김용수 한국물리학회 2014 Current Applied Physics Vol.14 No.5
CaTiO3 is a well-known incipient ferroelectric material that does not undergo a ferroelectric phase transition in spite of the intriguing dielectric constant behavior. Especially, unlike a prototypical incipient ferroelectric SrTiO3, the paraelectric state of CaTiO3 cannot be easily destroyed by small perturbations, including cation doping and epitaxial strain. We present that a nearly strain-free epitaxial CaTiO3 film grown at a low oxygen partial pressure exhibits polarizationevoltage hysteresis loops and the distinct difference of piezoresponse force microscopy phase signals, implying that a ferroelectric phase is induced. Such results are shown even at room temperature. We suggest that the observed ferroelectric behavior in CaTiO3 film comes from the defect dipoles composed of vacancies inside the film. Using electron-probe microanalysis and optical absorption spectra measurements, we found that CaTiO3 film has considerable Ca and O vacancies, forming the localized defect state in electronic structure. This work highlights the importance of vacancies and their clusters, such as defect dipoles, in understanding the electronic properties of perovskite oxide thin films, including ferroelectricity.