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Background: The influences of demographics, culture, language, and environmental changes on Mini-Mental State Examination (MMSE) scores are considerable.
Methods: Using a sample of 7452 healthy, community-dwelling elderly Koreans, aged 55 to 94 years, who participated in the four ongoing geriatric cohorts in Korea, we investigated demographic influences on MMSE scores and derived normative data for this population. Geropsychiatrists strictly excluded subjects with cognitive disorders according to the protocol of the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD-K) Clinical Assessment Battery (CERAD-K-C).
Results: Education (standardized β = 0.463), age (standardized β = −0.303), and gender (standardized β = −0.057) had significant effects on MMSE scores (p < 0.001). The score of MMSE increase 0.379 point per 1-year education, decrease 0.188 per 1-year older, and decrease 0.491 in women compared to men. Education explained 30.4% of the scores’ total variance, which was much larger than the variances explained by age (8.4%) or gender (0.3%). Accordingly, we present normative data for the MMSE stratified by education (0, 1–3, 4–6, 7–9, 10–12, and ≥ 13 years), age (60–69, 70–79, and 80–89 years), and gender.
Conclusions: We provide contemporary education-, age-, and gender-stratified norms for the MMSE, derived from a large, community-dwelling elderly Korean population sample, which could be useful in evaluating individual MMSE scores.
ZnS:Cu,Cl,Mn,Te, which shows red AC powder electroluminescence (ACPEL) emission, was synthesized using a conventional wet synthesis and a sealed vessel method. The photoluminescence (PL) and ACPEL were characterized. After the second firing, 0.5 wt% tellurium (Te)-doped ZnS:Cu,Cl,Mn,Te phosphor shows almost red PL emission from the 4T1–6A1 transition of Mn2+ ions, which are affected by the Te. Extended x-ray absorption fine structure analysis on the Mn K edge proved that the substitution of sulfur (S) with Te changes the local crystal field of the Mn2+ ions and shifts an orange emission (∼588 nm) to a red emission (∼650 nm). A red ACPEL emission is first shown in 0.5 wt%Te-doped ZnS:Cu,Cl,Mn,Te after the third firing phosphor even though its luminance is not very high. The origin of the ACPEL emission is assumed to be not a CuxS–ZnS p–n junction but a CuxTe–ZnS p–n junction. Raman spectra were characterized to support that the red ACPEL emission is probably attributed to a CuxTe–ZnS p–n junction.
Phase-sensitive synchrotron radiation (SR) radiography was combined with x-ray diffraction topography to study structural defects of SiC crystals. The particular bulk SiC crystals examined had a low micropipe density and a hexagonal habitus composed of prismatic, pyramidal, and basal faces well developed. X-ray diffraction topography images of the sliced (0001) wafers, which were formed due to the complex lattice distortions associated with defective boundaries, demonstrated the existence of two-dimensional defective boundaries in the radial direction, normal to the (0001) planes. In particular, those parallel to the 〈1120〉 directions extended rather far from the seed. On the other hand, by phase-sensitive SR radiography the effect of micropipe collection was detected. Micropipes grouped mostly in the vicinities of the defective boundaries but rarely appeared between groups. Some general remarks about possible reasons for the development of such peculiar defect structures were made.
We found the correlation between microstructure and surface evolution in the crystallization of amorphous α-Fe2O3/α-Al2O3(0001) thin films using real-time synchrotron x-ray scattering and atomic force microscope. The amorphous precursor is crystallized to the epitaxial α-Fe2O3 grains in three steps; i) the growth of the well aligned α-Fe2O3 interfacial islands on α-Al2O3(0001), ii) the growth of the misaligned, homoepitaxial, α-Fe2O3 grains on the well aligned grains ( > 400 °C), and iii) the nucleation of the heteroepitaxial misaligned grains directly on the α-Al2O3substrate ( > 600 °C). The surface roughing is caused by the microstructure evolution during the crystallization of the amorphous precursor films.
The highly strained interfacial structure and reaction of Co on Si(111) in the initial growth stage was studied by in-situ surface x-ray scattering. Co was deposited on Si(111) – (7×7) reconstruction by electron beam evaporation in ultra high vacuum. Our study reveals that the interfacial layer, formed by the reaction of Co with Si in the initial growth stage at room temperature, is a silicide layer with stoichiometry of Co2Si. The interfacial silicide layer is a commensurate phase of pseudohexagonal Co2Si, which shows a significant local atomic displacements imposed by Si substrate. The intensity oscillations at the anti-Bragg position with Co coverage show that a layer-by-layer consumption of silicon substrate occurs for the first 15 monolayers (ML) of Co deposited.
We investigated the structural evolution of the Ni/Au contact on GaN(000l) during annealing in N2, using in-situ x-ray diffraction, anomalous x-ray scattering, and high resolution electron microscopy. GaN decomposition occurred mostly along GaN dislocations at temperature higher than 500°C. The decomposed Ga diffused into Au and Ni substitutional positions, and the decomposed nitrogen reacted with Ni, forming Ni4N. Interestingly, Ni4N was grown epitaxially. The epitaxial relationship of the Ni4N, Au, and Ni was identified as M(111)//GaN(0002) and M[1 −1 0]//GaN[1 1 −2 0] (M= Ni4N, Au, and Ni). At dislocation free regions, however, the atomically smooth interface remained intact up to 700 °C. Remarkable improvement of device reliability is expected in the contact on dislocation free regions compared with the contact on dislocations.
In Pb(Zr0.4Ti0.6)O3 (PZT) (110-nm-thick) films grown on (001)-oriented LaNiO3 (LNO) (50-nm-thick)/Si(001) films by pulsed laser deposition, the microstructures and various structural properties of the PZT and the underlying LNO films were comparatively studied mainly using synchrotron x-ray scattering experiments. Basically, the PZT films resembled the LNO films in microstructure, crystal orientation, and mosaic distribution. The PZT films, however, showed an isotropic structural order (in- and out-of-plane coherence lengths: 18 and 14 nm) in contrast to the anisotropic order of the LNO films (in- and out-of-plane coherence lengths: 5 and 30 nm). The PZT/LNO/Si systems displayed a good hysteresis characteristic (remanent polarization, 11.8 μC/cm2; coercive field, 36.1 kV/cm). We confirmed that oriented PZT films with reasonable ferroelectric properties can be successfully prepared on properly textured LNO films at a relatively low processing temperature.
The thermal stability of RuO2/Si(100) films in air was studied using ex situ synchrotron x-ray scattering. The (110) textured RuO2 film showed good thermal stability due to the low surface and strain energies. However, the RuO2 films of high strain and surface energies were transformed to three-dimensional islands during annealing up to 800 °C. We also studied, during the post annealing process, the interface roughness of BaxSr1−xTiO3 (BST)/RuO2/Si(100) and BST/Pt/Ti/SiO2/Si(100) structures comparatively, using in situ synchrotron x-ray scattering. The interfaces of the BST/RuO2/Si were thermally stable up to 500 °C, and the deterioration of the interfaces above 500 °C was attributed to the crystallization of amorphous BST film. Meanwhile, the interfaces of the BST/Pt/Ti/SiO2/Si were significantly degraded even at the low temperature of 350 °C, mainly due to the formation of the Pt–Ti alloy and the Ti oxidation.
We investigated the structural behavior of the Ni/Au contact on GaN(000l) during annealing in N2, using in-situ x-ray diffraction, anomalous x-ray scattering, and high resolution electron microscopy. Thermally activated atomic mobility caused the two metal atoms, Au and Ni, to interdiffuse during annealing and form solid solutions. At temperature higher than 500°C, GaN decomposition and reactions occurred mostly along GaN dislocations. By decomposed nitrogen reacted with Ni, interestingly, epitaxial Ni4N phase was formed. The epitaxial relationship of the Ni4N, Au, and Ni was identified as M(111)//GaN(0002) and M[0 1 1]//GaN (M= Ni4N, Au, and Ni).
The structural evolution of GaN films during the initial growth process of metalorganic chemical vapor deposition (MOCVD) - low temperature nucleation layer growth, annealing, and high temperature epitaxial growth - was investigated in a synchrotron x-ray scattering experiment. The nucleation layer grown at 560°C that was predominantly cubic GaN consisted of tensile-strained aligned domains and relaxed misaligned domains. The hexagonal GaN, transformed from the cubic GaN during annealing to 1100 °C, showed disordered stacking. The atomic layer spacing decreased as the fraction of the hexagonal domains increased. Subsequent growth of epitaxial GaN at 1100 °C resulted in the formation of ordered hexagonal GaN domains with rather broad mosaicity.
We have investigated surface treatment effect on the interfacial reaction of Pd/p-GaN interface and also room temperature ohmic contact formation mechanism of Pd-based ohmic contact. In order to examine room temperature ohmic behavior, various metal contact systems were deposited and current-voltage measurements were carried out. In spite of large theoretical Schottky barrier height between Pd and p-GaN, Pd-based contact showed perfect ohmic characteristic even before annealing. According to the results of synchrotron X-ray radiation, the closed-packed atomic planes (111) of the Pd film were quite well ordered in surface normal direction as well as in the in-plane direction. The effective Schottky barrier height of Au/Pd/Mg/Pd/p-GaN was 0.47eV, which was estimated by Norde method. This discrepancy between theoretical barrier height and the measured one might be due to the epitaxial growth of Pd contact metal and so the room-temperature ohmic characteristic of Pd-based ohmic contact was related strongly to the in-plane epitaxial quality of metal on p-GaN.
An epitaxial BaTiO3 film with 290-nm thickness was prepared on a MgO(001) single-crystal substrate by radio-frequency magnetron sputter deposition. The structural characteristics of the film were studied as a function of temperature in in situ, real-time synchroton x-ray scattering experiments. We found that the as-grown film was strained at room temperature and tetragonally distorted with the c axis normal to the film surface. Interestingly, its lattice parameters were found to be expanded 1.28% and 0.64% in both the in-plane and the out-of-plane directions, respectively (i.e., biaxially), comparing to those of a bulk BaTiO3. More importantly, as it was heated to 600 °C, the tetragonal structure was kept up without the phase transition, which is usually observed in other epitaxial ferroelectric thin films.
Epitaxial (Ba0.5Sr0.5) TiO3 thin films of two different thickness (∼25 and ∼134 nm) on MgO(001) prepared by a pulsed laser deposition method were studied by synchrotron x-ray scattering measurements. The film grew initially with a cube-on-cube relationship, maintaining it during further growth. As the film grew, the surface of the film became significantly rougher, but the interface between the film and the substrate did not. In the early stage of growth, the film was highly strained in a tetragonal structure (c/a = 1.04) with the longer axis parallel to the surface normal direction. As the growth proceeded further, it relaxed to a cubic structure with the lattice parameter near the bulk value, and the mosaic distribution improved significantly in both in- and out-of-plane directions. The thinner film (∼25 nm) showed only one domain limited mainly by the film thickness, but the thicker film (∼134 nm) exhibited three domains along the surface normal direction.
The bombarding energy dependence of bonding structure in amorphous carbon interlayer and its effect on diamond nucleation density (Nd) were studied. Amorphous carbon (a-C) interlayer was deposited by magnetron sputtering. Interestingly, the intensity ratio (ID/IG) of the D band (∼1400 cm−1) to the G band (∼1570 cm−1) in the Raman spectra and the optical band gap of the a-C film were found to be inversely proportional to the sputtering power, that is, to bombarding energy. When diamond was subsequently deposited at 800 °C by microwave plasma chemical vapor deposition (CVD), diamond could be grown only on the interlayers with higher ID/IG (≥2.20), and Nd was increased up to 2 × 106/cm2 with the increase of ID/IG ratio, that is, with the decrease of the bombarding energy. We experimentally confirmed that the amount of the sp3 bonded carbon clusters within the interlayer was dependent on the bombarding energy of the particles, determining the diamond nucleation density. We suggest that the transformation of the amorphous carbon into graphitic carbon should be effectively prevented for the diamond nucleation on the a-C interlayer.
The structural evolution of GaN films during the initial growth process of metalorganic chemical vapor deposition (MOCVD) - low temperature nucleation layer growth, annealing, and high temperature epitaxial growth - was investigated in a synchrotron x-ray scattering experiment. The nucleation layer grown at 560°C that was predominantly cubic GaN consisted of tensile-strained aligned domains and relaxed misaligned domains. The hexagonal GaN, transformed from the cubic GaN during annealing to 1100°C, showed disordered stacking. The atomic layer spacing decreased as the fraction of the hexagonal domains increased. Subsequent growth of epitaxial GaN at 1100°C resulted in the formation of ordered hexagonal GaN domains with rather broad mosaicity.
The preferred orientation of the TiN film grown by sputter-deposition was studied by the cross-sectional TEM. The preferred orientation was changed from the (200) through the (110), and then finally to the (111) with the film thickness. The cross-sectional microstructure also shows that the film consists of three layers which are all columnar structure. The (111) preferred orientation was observed in the top layer, and the (110) in the middle layer, and finally the (200) in the bottom layer. It is very surprising that the (110) preferred orientation could be observed in a medium thickness region and there are two kinds of critical thicknesses. These results surely show the strong dependence of the change in the preferred orientation on the strain energy in TiN thin films.
Diamond was deposited at 850 °C by microwave plasma chemical vapor deposition (CVD) on the interlayers with various intensity ratios (ID/IG) of the D band (~1400 cm-1) to the G band (~1570 cm-1) in the Raman spectra. Diamond could be grown only on the interlayers with higher ID/IG (≤1.95), and Nd was slightly increased to 3 × 106/cm2with ID/IG. The predeposition at 350 °C, which decreased the full-width at half-maximum of the broad D band, further increased Nd to 5 × 107/cm2. With 300 ÅA Pt overlayer on the interlayer, Nd was much more enhanced to 8 × 107/cm2. We suggest the sp3 bonded carbon clusters within the interlayer contribute to diamond nucleation, but they should be survived against atomic hydrogen etching during diamond deposition by increasing the sp3/sp2 ratio, by increasing the degree in clustering, or by protecting them with overlayer.
Effects of interlayers on diamond nucleation were investigated for the Si substrates. Interlayers were deposited on the diamond-abraded Si substrates by rf sputtering prior to diamond growth using microwave plasma chemical vapor deposition (CVD). Compared with 1 × 108/cm2 for the just abraded substrate, the nucleation density was greatly enhanced to 1 ∼ 2 × 109/cm2 by 50 nm thick interlayer, irrespective of the kind of interlayer material used in this study (Si, Mo, Ti, Pt, Ag, TiN, or SiO2). As the thickness of the Si interlayer increased from 20 to 500 nm, the nucleation density reached a maximum value, 3 × 109/cm2 at 100 nm. However, the growth rate was monotonically reduced from ∼300 nm/h to ∼100 nm/h. For the 700 nm thick Si interlayer, no diamond growth was observed. These results indicate that there is an optimum interlayer thickness around 100 nm for the higher nucleation density. The role of the interlayer in enhancing the nucleation density is believed to protect the nucleation sites generated by the diamond abrasion, otherwise they could be considerably etched away by atomic hydrogen during the initial diamond deposition.
The effects of secondary pretreatments on diamond nucleation were investigated for the Si substrates pretreated by the diamond abrasion. When the substrate was just abraded with diamond powder, the nucleation density of diamond was 7 × 108/cm2. However, the nucleation density was found to be greatly decreased by various secondary pretreatments except by one wet chemical etching method. The nucleation density was reduced to 3 × 107/cm2 by the chemical etching (I), to 7 × 106/cm2 by the H2 plasma etching, and to ∼104/cm2 by the Ar sputtering, or O2 plasma etching. It was very slightly reduced to 3 × 108/cm2 by the chemical etching (II). The effects of secondary pretreatments in reducing the nucleation density were found to be very closely related to the removal of diamond seeds rather than topographic sites or structural defects. Therefore, diamond seeds generated by the diamond abrasion are considered as the main nucleation sites of diamond.
Recently it was observed through cross-sectional TEM that the preferred orientation of the TiN thin film was changed from (200) to (111) with thickness. In this study, the process of the change in the preferred orientation was studied near the critical thickness by x-ray diffraction, and the value of the critical thickness could be estimated. The change of the critical thickness was also investigated with the strain energy per unit volume. The strain energy could be changed by controlling the energy of the bombarding particle, i.e., by adjusting the rf power, the working pressure, and the substrate bias in sputtering. The critical thickness was decreased monotonically in all cases as the energy of the bombarding particle or the strain energy per unit volume was increased. These results surely show the dependence of the change of the preferred orientation on the strain energy in the TiN thin films.
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