• The Korean Journal of Ceramics
• /
• v.6 no.2
• /
• pp.110-115
• /
• 2000

$SrBi_2Ta_2O_9$ thin films were deposited at room temperature on the usual (111) oriented Pt bottom electrodes using r.f. magnetron sputtering, and then post-annealed at 650-$800^{\circ}C$ for 30min in oxygen flow. Low temperature processing which shows the preferred oriented SBT thin films was obtained by controlling the sputtering pressure and/or Sr content in target. The orientation and grain growth behavior of SBT thin films were dependent on Sr contents in films. With increasing the excess Bi content up to 50% in SBT thin films, it was possible to lower the onset temperature of grain growth. The c-axis preferred oriented SBT thin films were well-grown under the condition of low post-annealing($650^{\circ}C$) by lowering post-annealing pressure. After $10^{11}$ switching cycles, no polarization degradation was observed in both preferred oriented SBT capacitors.

• Korean Journal of Materials Research
• /
• v.21 no.5
• /
• pp.268-272
• /
• 2011

Due to their novel properties, GaN based semiconductors and their nanostructures are promising components in a wide range of nanoscale device applications. In this work, the gallium nitride is deposited on c-axis oriented sapphire and porous SWCNT substrates by molecular beam epitaxy using a novel single source precursor of $Me_2Ga(N_3)NH_2C(CH_3)_3$ with ammonia as an additional source of nitrogen. The advantage of using a single molecular precursor is possible deposition at low substrate temperature with good crystal quality. The deposition is carried out in a substrate temperature range of 600-750$^{\circ}C$. The microstructural, structural, and optical properties of the samples were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and photoluminescence. The results show that substrate oriented columnar-like morphology is obtained on the sapphire substrate while sword-like GaN nanorods are obtained on porous SWCNT substrates with rough facets. The crystallinity and surface morphology of the deposited GaN were influenced significantly by deposition temperature and the nature of the substrate used. The growth mechanism of GaN on sapphire as well as porous SWCNT substrates is discussed briefly.

• Korean Journal of Materials Research
• /
• v.16 no.8
• /
• pp.479-484
• /
• 2006

Highly c-axis oriented poly-crystalline GaN with a dimension of $1{\sim}3\;{\mu}m$ was deposited on $c-Al_2O_3$ substrate by vapor transport epitaxy (VTE) method at the temperature range of $900{\sim}1150^{\circ}C$. XRD intensities from (00'2) plane of grown GaNs were increased with reaction conditions which indicate the improvement of the crystal quality. In the PL spectra measured at 10 K, the spectrum composed with the neutral-donor bound exciton-related emission at 3.47 eV, crystal defect-related emission band at 3.42 eV and with its phonon replicas. The fact that intensity of $I_2$ were increased and FWHM were decreased with growth conditions means that the quality of GaN crystals were improved. With this simple VTE technology, we confirm that the GaNs were simply deposited on sapphire substrate and crystal quality related to optical properties of GaN grown by VTE were relatively good. PL emission without deep level emission in spite of polycrystalline structure can be applicable to the fabrication of large area and low cost optical devices using poly-GaN grown by VTE.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.10
• /
• pp.828-833
• /
• 2000

Growth characteristics and microstructure of AIN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the micorstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.111-114
• /
• 2000

Growth characteristics and microstructure of AlN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the microstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.14 no.5
• /
• pp.557-565
• /
• 2014

We report the effect of basal-plane stacking faults (BSFs) on X-ray diffraction (XRD) of non-polar (11$\underline{2}$0) a-plane GaN films with different $SiN_x$ interlayers. Complete $SiN_x$ coverage and increased three-dimensional (3D) to two-dimensional (2D) transition stages substantially reduce BSF density. It was revealed that the Si-doping profile in the Si-doped GaN layer was unaffected by the introduction of a $SiN_x$ interlayer. The smallest in-plane anisotropy of the (11$\underline{2}$0) XRD ${\omega}$-scan widths was found in the sample with multiple $SiN_x$ layers, and this finding can be attributed to the relatively isotropic GaN mosaic resulting from the increase in the 3D-2D growth step. Williamson-Hall (WH) analysis of the (h0$\underline{h}$0) series of diffractions was employed to determine the c-axis lateral coherence length (LCL) and to estimate the mosaic tilt. The c-axis LCLs obtained from WH analyses of the present study's representative a-plane GaN samples were well correlated with the BSF-related results from both the off-axis XRD ${\omega}$-scan and transmission electron microscopy (TEM). Based on WH and TEM analyses, the trends in BSF densities were very similar, even though the BSF densities extracted from LCLs indicated that the values were reduced by a factor of about twenty.

• The Korean Journal of Ceramics
• /
• v.3 no.4
• /
• pp.253-256
• /
• 1997

Epitaxially grown Pb(Zr, Ti)O$_3$thin films were prepared on LaAlO$_3$substrates by the dipping pyrolysis process using metal naphthenates as starting materials Homogeneous Pb-Zr-Ti solutions with toluene were spin-coated onto the substrates and pyrolyzed at 50$0^{\circ}C$ Highly oriented Pb(Zr, Ti)O$_3$films confirmed by X-ray diffraction $\theta$-2$\theta$ scans were obtained by heat-treated at 75$0^{\circ}C$ in air The X-ray pole-figure analysis and reciprocal-space mapping of the resulting 0.6$\mu\textrm{m}$ films showed that the thin films comprising the c-axis oriented tetragonal phase have an epitaxial relationship with the LaAlO$_3$substrates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.429-432
• /
• 1999

The growth of $\textrm{YMnO}_3$ films directly on Si(100) substrates by RF magnetron sputtering system has been performed. The structural properties of $\textrm{YMnO}_3$ films on Si(100) by rapid thermal annealing(RTA) analysed by XRD(X-ray diffraction). The c-axis oriented $\textrm{YMnO}_3$ peaks were observed deposited in $\textrm{YMnO}_3$/Si(100) structure at RF power of 100W and at a temperature range of $840^{\circ}C$~$870^{\circ}C$ in oxygen ambient.

• Journal of the korean society of oceanography
• /
• v.32 no.1
• /
• pp.28-37
• /
• 1997

Two marine bivalve shells were collected from the eastern and western coastal regions of Korea, respectively. Stable oxygen and carbon isotope profiles are constructed using the incremental sampling along the axis of maximum growth to provide the continuous ${\delta}^{18}$O and ${\delta}^{13}$C records, which register the physical, biological and chemical properties of seawater where the organisms live. Cycles in the ${\delta}^{18}$O profiles are interpreted as annual along with the identification of annual growth bands; the maximum ${\delta}^{18}$O values correspond with the coldest temperature of seawater whereas the minimum ${\delta}^{18}$O values with the warmest temperature. The primary control on the amplitude of the ${\delta}^{18}$O profiles is seasonal variation of seawater temperature. The offset of the baseline between ${\delta}^{18}$O values of the two specimens is attributed to differences in both temperature and seawater ${\delta}^{18}$O values between two localities. The ${\delta}^{13}$C profiles show the similar seasonality of carbon cycling associated with phytoplankton productivity. The offset in the ${\delta}^{13}$C profiles between two specimens may be, as in the case of oxygen isotope profile, attributed to the different ${\delta}^{13}$C value of the seawater DIC (dissolved inorganic carbon) between the western coast and the eastern coast. Relationships between the shell isotopic composition and the coastal water properties of shell growth are readily interpreted from the ${\delta}^{18}$O-${\delta}^{13}$C pair diagram of the shell isotope data, similar to the use of salinity-${\delta}^{18}$O diagram for identifying water masses. The preliminary stable isotope results of this study suggest that mollusk shell isotope geochemistry may be useful to monitor the properties of water masses in the coastal and inner shelf setting around Korea and improve the interpretation of paleoceanography, provided the fossil mollusks are well preserved.

• Journal of the Microelectronics and Packaging Society
• /
• v.20 no.1
• /
• pp.33-37
• /
• 2013

In this research, we investigated the effect of mole concentration of precursor on morphological, structural and optical properties of ZnO nanorods. ZnO nanorods were hydrothermally grown on c-plane sapphire substrates in aqueous solution which contains zinc nitrate hexahydrate and hexamethylenetetramine at 90oC in the precursor range of 0.01 M to 0.025 M. With the increase of mole concentration, length and diameter of ZnO nanorods increased. In all the conditions, the growth direction of rods was longitudinally c-axis direction. From the strong emission peak at 380 nm of PL spectra at room temperature, we could confirm that the crystal quality of ZnO nanorods is good to emit radiative recombination spectra.