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There are growing concerns about the impact of the COVID-19 pandemic on the mental health of older adults. We examined the effect of the pandemic on the risk of depression in older adults.
We analyzed data from the prospective cohort study of Korean older adults, which has been followed every 2 years. Among the 2308 participants who completed both the third and the fourth follow-up assessments, 58.4% completed their fourth follow-up before the outbreak of COVID-19 and the rest completed it during the pandemic. We conducted face-to-face diagnostic interviews using Mini International Neuropsychiatric Interview and used Geriatric Depression Scale. We performed generalized estimating equations and logistic regression analyses.
The COVID-19 pandemic was associated with increased depressive symptoms in older adults [b (standard error) = 0.42 (0.20), p = 0.040] and a doubling of the risk for incident depressive disorder even in euthymic older adults without a history of depression (odds ratio = 2.44, 95% confidence interval 1.18–5.02, p = 0.016). Less social activities, which was associated with the risk of depressive disorder before the pandemic, was not associated with the risk of depressive disorder during the pandemic. However, less family gatherings, which was not associated with the risk of depressive disorder before the pandemic, was associated with the doubled risk of depressive disorder during the pandemic.
The COVID-19 pandemic significantly influences the risk of late-life depression in the community. Older adults with a lack of family gatherings may be particularly vulnerable.
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.
MgO thin films are widely used in plasma display panels (PDPs) to protect the dielectric layer, which is composed of PbO2, B2O3, and SiO2 compound, against ion bombardment during discharge. To improve the electrical properties of the MgO thin films, (Ba,Sr,Ca)CO3 or LaB6, which has a lower work function than that of MgO, added to the MgO films. The effects of (Ba,Sr,Ca)CO3 or LaB6 addition on the electrical properties, microstructure, and electronic band structure were investigated. In the case where (Ba,Sr,Ca)CO3 was added, the firing voltage, which is the voltage when the panel is ignited the first time during increasing input voltage, was about 18.4 V lower than that of the conventional MgO films. In the case where LaB6 was added, the firing voltage was also reduced by about 24 V. The luminance and luminous efficiency were also increased. Of particular interest was the valence band spectra changed after adding (Ba,Sr,Ca)CO3 or LaB6. The valence band edge, which is the top of the valence band, was shifted to lower binding states and the width of the valence band was increased. Moreover, the band gap was slightly reduced. Considering the emission mechanism of MgO films in plasma display panels, these results mean that the secondary electrons can be ejected more easily and the ejected electrons have more energy. Therefore, the addition of (Ba,Sr,Ca)CO3 or LaB6 might improve the electrical properties.
The importance of the secondary electron emission of the protective layer in the alternating current plasma display panels is widely known. However, the difficulty in measuring the secondary electron emission coefficients (γ) of insulating materials has hampered efforts to obtain accurate estimates of their values. To overcome the difficulty of direct measurement, we devised a calculating γ using the spectra of x-ray photoelectron spectroscopy (XPS) and a well-defined theory. The XPS spectra of the valence and core bands of MgO, Al2O3, and Y2O3 films, which were deposited by e-beam evaporation, were measured. Calculations of the γ values were conducted for the case when gas ions such as He, Ne, Ar, and Xe slowly approach the solid surface.
Carbon nanotubes (CNTs) were grown using a dc arc discharge process and relevant process parameters were investigated. Unlike the usual process in which a carbon anode is filled with metal catalyst powder, CNTs were prepared using a carbon cathode on which the metal catalyst had been deposited using an electroplating system. Various transition metals, Ni, Co and Ti, were used as a catalyst. The results show that multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) can both be synthesized using this technique. And yield and morphology of the prepared CNTs varied depending on the experimental condition and catalyst. While MWNTs were produced in the deposit and soot sample, SWNTs with diameters near 1nm were only detected in the soot collects. When Ni film was used as a catalyst, the yield of SWNTs was higher than in case of using Co or Ti film as a catalyst. From these results, the optimized preparing condition of CNTs and the properties of a good catalyst are discussed.
The electrical conduction mechanisms of approximately 8-nm-thick Ta2O5 films grown by metalorganic chemical vapor deposition were investigated by measuring the current density–voltage characteristics at various temperatures. The Ta2O5 films were grown in two steps with or without intermittent annealing at 450 °C under an O3 atmosphere with ultraviolet light radiation (UV-O3 treatment). High-resolution transmission electron microscopy of the films after post-deposition annealing at 750 °C under an O2 atmosphere showed that the intermittent UV-O3 treatment improved the crystallization of the film during post-annealing. Auger electron spectroscopy of the variously treated samples showed that the improvement in crystallization was due to the increase in the oxygen concentration of the Ta2O5 films by the UV-O3 treatment. The Ta2O5 film without the UV-O3 treatment mostly exhibited a Poole–Frenkel conduction behavior with the electron trap level of 0.62 eV from the conduction band edge. The whole layer UV-O3 treated Ta2O5 films also showed a Poole–Frenkel conduction behavior with an almost identical electron trap level and a reduced density. The partially UV-O3 treated Ta2O5 films exhibited a direct tunneling behavior in a relatively low voltage region by the tunneling through the thin (∼3.8 nm) UV-O3 treated surface layer. However, these films showed a Poole–Frenkel conduction behavior in the high-voltage region. In general, the UV-O3 treatment was an efficient method to reduce the leakage current of the high-dielectric Ta2O5 films.
Pt thin films of various thicknesses (30 nm ∼ 200 nm) were deposited on Si wafers with SiO2, Ti, TiO2, or IrO2 buffer layers at various temperatures (room temperature ∼200 °C) by a direct current magnetron sputtering process. The Pt films showed a strong (111)-preferred texture irrespective of the thickness, under-layer, and growth temperature. The authors previously reported [J-E. Lim, D-Y. Park, J.K. Jeong, G. Darlinski, H.J. Kim, and C.S. Hwang, Appl. Phys. Lett. 81, 3224 (2002)] that the films were composed of three kinds of grains with slightly different (111) lattice parameters (bulklike, 1.0% and 2.1% larger). This study details the microstructural variations of the Pt films according to the variations of experimental parameters. The different deposition conditions produced slightly different crystalline structures, but the three different (111) lattice parameters were always found. Epitaxial (200) Pt films on a (200) MgO substrate and a highly (111) textured Au thin film on a SiO2/Si did not show the same splitting in the lattice parameter. The grains with 1.0% and 2.1% larger (111) lattice parameter almost disappeared after postannealing at 1000 °C. However, surface chemical binding of the Pt film before and after annealing was unchanged. Therefore, it is believed that the lattice parameter splitting in the (111) textured Pt film originated from the interfacial grains with the distorted crystal structure due probably to growth stress.
MgO single crystals and thin films were intentionally hydrated to determine the critical factors affecting the hydration behavior. The degree of hydration was affected by the crystallographic orientation in the initial stages. The (111) plane showed a higher tendency to hydrate than (100). The shape of the hydration clusters also differed according to the orientation of MgO single crystals. After long-term hydration, the density and grain size appeared to influence the hydration along with the orientation. On low-density thin films, Mg atoms are easily supplied to the surface, which induces large hydration clusters. As the grain boundary area increased, the number of nucleation sites for the formation of hydration clusters increased, which increases the number of clusters. Hydration also occurred in the inner part of thin films. The density of thin films is the most important property in this case because it governs the diffusion of Mg atoms, water, and OH through the thin films.
Surface acoustic wave (SAW) propagation properties of gallium nitride (GaN) epitaxial layers on sapphire were theoretically and experimentally characterized. GaN thin films were grown on a c-plane sapphire substrate using a metalorganic chemical vapor deposition system. The experimental characterization of SAW propagation properties was performed with a linear array of interdigital transducer structures, while SAW velocities were calculated by matrix methods. Experimentally, we found pseudo-SAW and high-velocity pseudo-SAW modes in the GaN/sapphire structure, which had a good agreement with calculated velocities.
6H-SiC single crystals were grown on various substrates, treated mechanically and chemically in different conditions, by physical vapor transport. To investigate the defect evolution according to the different substrate treatment prior to the growth, the grown crystals were examined by optical micrograph, scanning electron microscopy, atomic force microscopy and molten KOH etching technique. The smoother substrate surface was, the lower defect density the grown SiC had. The highest quality SiC crystal was grown on substrate etched by hydrogen after polished by 0.25 νm diamond paste, having an edge/screw dislocation density of 7.3 ×102 / cm2 without micropipes. Defects, such as dislocations and micropipes, of the grown crystals are found to be strongly correlated with the substrate morphology.
We investigated the effect of substrate surface roughness on c-axis preferred orientation of ZnO films deposited by radio frequency (rf) magnetron sputtering. We used as substrates a bare Si(100), evaporated Au/Si(100), evaporated Al/Si(100), and sputtered Al/Si(100), of which rms roughness by atomic force microscope (AFM) were 0.127, 1.71, 2.11, and 6.5∼11.8 nm, respectively. The crystallinity and the c-axis preferred orientation of ZnO films strongly depended on the surface roughness of the used substrates.
MgO and Mg1-xTixO thin films were deposited by the electrostatic spray deposition method using Mg(tmhd)2 and Ti(OiPr)2(tmhd)2 as source materials and tetrahydrofuran and 1-octyl alcohol as solvents. The refractive index of the films shows a strong change from 1.73 for MgO to 2.39 for TiO2. The optical band gap energy values are 3.83 eV for TiO2 film and higher than 5.1 eV for films of Mg/(Mg+Ti) > 0.67. The discharge voltage and current increased with a content of Ti in Mg1-xTixO films. All these changes are closely associated with different Mg/(Mg+Ti) ratios of the films.
Carbon-containing silicon oxide (SiOC) is regarded as a potential low dielectric constant (low-κ) material for an interlayer dielectric (ILD) in next generation interconnection. In this study, we present the fundamental film properties and integration process compatibility of the low-κ SiOC film deposited by using bistrimethylsilylmethane (BTMSM) precursor. As more carbon was incorporated into film, both film density and dielectric constant decreased. The lowest κ-value, which we have obtained in this study, was 2.3 and the hardness of SiOC film was 1.1GPa as well as showing the thermal stability up to 500°C. In case of using conventional gases, organic components in SiOC film restricted etch rate. However, O2 addition could make it possible to obtaine a reasonable etch rate. The post-treatment of SiOC film in hydrogen plasma improved the resistance to O2 plasma in ashing process. The compatibility of SiOC film to the CMP process was also examined.
Pb(Zr, Ti)O3 (PZT) thin films were deposited on Pt/SiO2/Si substrates by metalorganic chemical vapor deposition using solid delivery system. The effects of deposition parameters such as the substrate temperature, the concentration of Pb precursor in the precursor mixtures, and the reactor pressure on the structural and electrical properties of PZT thin films were investigated. To obtain single-phase PZT thin films, the optimal range of the substrate temperature should be between 600 and 650 °C. The PbO content in PZT thin films was proportional to the fraction of Pb in the precursor mixture below 550 °C, but it was independent of the fraction of Pb in the mixture above 600 °C. With the increment of the reactor pressure, Zr contents in PZT thin films were increased, and the Pb/(Zr + Ti) ratio became more stoichiometric so that the ferroelectric properties were improved.
(Bi,La)4Ti3O12(BLT) thin films were prepared on Si(100) substrates by the pulse injection metalorganic chemical vapor deposition (MOCVD) process, in which Ti and La precursors were injected with periodic pauses while Bi precursor was supplied continuously. In case of the pulse injection method, the film composition was relatively uniform and the Bi content at the interface was relatively uniform and the Bi content at the interface was increased. The BLT films, which were deposited by the pulse injection MOCVD, showed better crystallinity and thinner ionterfacial amorphous layer than the continuous BLT films. The continuous BLT films, although measured at 1 MHz showed similar C-V characteristics to those measured at low frequency region, and their flatband voltages also shifted severely to the negative voltage direction. On the other hand, the pulse BLT films exhibited clockwise ferroelectric hysteresis in the C-V curves. The memory window and the leakage current density were about 2V and 1.46×10−7 A/cm2 at 9V (180 kV/cm), respectively.
Structure and composition of the ferroelectric Pb(Zr, Ti)O3 layers in a capacitor of the ferroelectric random-access memory (FeRAM) device having a density of 64 k were investigated by transmission electron microscopy (TEM) together with the energy-dispersive spectroscopy (EDS) technique. The 250 nm thick PZT layer derived by the sol-gel route showed a 2–3% Pb-deficient, 3–4% Ti-deficient, and 5–7% Zr-excess composition at the top electrode interface compared to the bulk composition when they were as-fabricated. The local compositional nonuniformity became more critical as the integration process proceeded, which seriously degraded the ferroelectric hysteresis and the device yield. The major cause of the compositional variation was the outward diffusion of Pb through the capping barrier TiO2 layer during annealing at 650 °C. The AlN capping barrier layer was also not effective in suppressing the diffusion of Pb. However, the Al2O3/TiO2 double capping layer was very effective in suppressing the outward diffusion of Pb, and excellent ferroelectric characteristic was expected.
The microstructural evolution, including preferred orientation and surface morphology, of ZnO films deposited by rf magnetron sputtering was investigated with increasing film thickness. Preferred orientation of the ZnO films changed from (0002) → (1011) → (1120) and fine and dense columnar grains also changed to large elongated grains with increasing thickness. Such selective texture growth was explained with an effect of highly energetic species bombardment on the growing film surface. The relationship between preferred orientation change and microstructural evolution was also discussed.
We deposited (Mn,Zn,Fe)1−xO thin films of a wüstite structure on SiO2/Si(100) by ion beam sputtering using a single-crystal Mn-Zn ferrite target. The wüstite structure of the as-deposited film, confirmed by XRD, TEM, and XPS analysis, appeared to originate from an oxygen-deficit ambient and also from the preferential resputtering of the oxygen ions in films during deposition. The as-deposited films showed ferrimagnetic characteristics having quite a large Ms in spite of their crystallographic structure, wüstite. Such an unusual phenomenon is presumably due to the different magnetic moments of the constituent cations with disordered distribution. This wüstite phase could be transformed into the spinel ferrite phase with the same preferred orientation during postannealing under an appropriate oxygen partial pressure. The interplanar distance of the as-deposited films decreased with increasing Ts due to a release of compressive stress. The Ms of the film had a maximum value at about 275 °C, while the resistivity, mainly governed by the grain boundaries, was almost the same irrespective of Ts.
We have investigated the effects of process parameters such as rf power, substrate, and gas pressure PAr on preferred orientation, microstructure, and magnetic properties of Ni-Zn-Cu ferrite thin films deposited by conventional rf magnetron sputtering. The texture structure was developed in the ferrite films deposited on the SiO2/Si(100) substrate at low rf power conditions. The ferrite film on the Si(111) substrate always had (111) texture irrespective of process parameters due to lattice matching, but the texture of the ferrite film on SiO2/Si(100) changed from (111) to (100) and finally returned to (111) orientation again with decreasing PAr. Such behavior would occur presumably due to the characteristic atomic stacking sequence corresponding to a given condition of the ion bombardment. The ferrite films deposited at low PAr had a denser microstructure consisting of tightly packed columnar grains with a smoother surface, better adhesion to the substrate, and better crystallinity than those at high PAr. Hc‖ of ferrite film deposited at low PAr was larger than that at high PAr and also larger than Hc⊥ of that deposited at the same PAr because larger compressive stress was induced at low PAr than at high PAr.
ZrO2 thin films were deposited at 1 atm on Si substrates by oxidation-assisted thermal decomposition of zirconium-trifluoroacetylacetonate in the temperature range of 300–615 °C. Above a deposition temperature of 400 °C, the deposited thin films have a columnar grain structure, where each grain is perpendicular to the substrate surface with a c-axis preferred crystallographic orientation, and have poor electrical characteristics as a dielectric thin film. But the thin film deposited at 350 °C has a fine equiaxed microcrystalline structure and has superior electrical characteristics of a breakdown field of 1 MV/cm and a relative dielectric constant of 27.