Electrical properties of graphene/In2O3 bilayer with remarkable uniformity as transparent conducting electrode.

A graphene/In2O3 bilayer (termed as GI-bilayer) is proposed as a transparent conducting electrode with remarkably improved areal-uniformity. To fabricate this new structure, an In2O3 layer with a thickness of less than 50 nm was grown by atomic layer deposition and then a graphene layer was grown by chemical vapor deposition and subsequently transferred onto the as-grown In2O3 layer. Electrical and optical properties of the GI-bilayer were systematically studied to verify effects of the underlying In2O3 layer. Hall measurements and following analysis showed a conductance enhancement of the GI-bilayer owing to p-type doping of graphene. Specifically, Raman analysis and ultraviolet photoelectron spectroscopy were performed to prove p-type doping of the graphene in the GI-bilayer. In addition, the GI-bilayer exhibited the significantly improved uniformity of the sheet resistance compared to that of a conventional monolayer of graphene. There was a duality on the role of the In2O3 underlayer in the GI-bilayer. It acted as a dopant layer to the graphene and lowered the sheet resistance from 863 to 510 Ω/sq as well as compensated microscale defects on graphene. More importantly, the In2O3 underlayer resulted in the extremely reduced standard deviation of sheet resistance from 150 to 7.5 Ω/sq over the area of 49 cm2.

Effect of nitrogen-doping on drain current modulation characteristics of an indium-gallium-zinc oxide thin-film transistor.

The effect of nitrogen-doping (N-doping) in an indium-gallium-zinc oxide (IGZO) channel layer on the analog, linear, and reversible drain current modulation in thin-film transistors (TFTs) with Al-top-gate/SiOx/TaOx/IGZO stack is investigated for potential application to artificial synaptic devices. The N-doped devices exhibit a more linear increase of drain current upon repeating positive gate biasing, corresponding to synaptic potentiation, while the undoped device shows a highly non-linear and abrupt increase of drain current. Distinct from the increase of drain current at positive biasing for potentiation, the decrease of drain current for depression behavior at negative biasing is found to be the same. Whereas the increase of drain current becomes more linear, the channel conductance, the magnitude of its change, and its changing speed are decreased by the N-doping. The partial replacement of oxygen with nitrogen, having higher binding energy with metal-cations, suppresses oxygen vacancy formation, then decreases the channel conductance. It also retards the migration of oxygen ions, then leads to a linear increase of drain current. These results reveal that the characteristics of tunable drain current such as its linearity, dynamic range, and speed could be controlled by altering the internal state of the IGZO channel, which is crucial for application to an artificial synapse in a neuromorphic system.

Optimal Nitrogen Incorporation in Nickel Silicide for Thermally Stable Contact Formation.

Nickel silicide (NiSi) is commonly used as a contact material for metal junctions but the poor thermal instability of NiSi above 600 °C has limited the further scaling down of devices and the implementation of novel schemes, such as monolithic 3-dimensional integration. This paper suggests a process to improve the thermal stability of NiSi through nitrogen incorporation during the silicidation process. The optimal level of nitrogen incorporation in NiSi reduced the nickel diffusion rate and enhanced the thermal stability by preventing the formation of a nickel disilicide phase. On the other hand, a higher level of N incorporation led to Ni3N formation, which impeded the complete transformation to NiSi. Therefore, it is essential to incorporate the optimal content of N. In this study, NiSi with 3.9% N incorporation showed superior electrical characteristics, such as the sheet resistance, junction leakage, and stable Schottky barrier height, even after high-temperature post silicidation annealing at 600 °C for 30 min.

Relationship between the use of hair products and urine benzophenone-3: the Korean National Environmental Health Survey (KoNEHS) cycle 4.

Background: Benzophenone-3 is a type of ketone with 2 benzene rings attached to a carbonyl group (C=O) and one benzene ring attached to a hydroxyl group (-OH). As an endocrine-disrupting chemical, benzophenone-3 is known to be associated with reproductive, developmental, thyroid, and endocrine toxicities. Benzophenone-3 is commonly used in hair products, cosmetics, and ultraviolet (UV) filters because of its characteristic property to absorb UV light. This study aims to investigate the association between the use of hair products and urine benzophenone-3 using the data from the Korean National Environmental Health Survey (KoNEHS) cycle 4 (2018-2020), which represents the Korean population. Methods: Using the KoNEHS cycle 4 survey, the data of 3,796 adults aged ≥ 19 years were analyzed. Based on the 75th percentile concentration of urine benzophenone-3, the participants were divided into the low- and high-concentration groups. Chi-square test was conducted to analyze the association of urine benzophenone-3 with distribution of general characteristics, use of personal care products, consumption of marine foods, and use of plastic products as the variable. Logistic regression analysis was conducted to calculate odds ratios (ORs) for the high-concentration group of urine benzophenone-3 based on the use of hair products. Results: Women with < 6 times or ≥ 6 times of hair product usage had significantly higher adjusted ORs compared to those who did not use hair products. The calculated ORs were 1.24 (95% confidence interval [CI]: 1.12-1.38) for women with < 6 times of usage and 1.54 (95% CI: 1.33-1.79) for women with ≥ 6 times of usage. Conclusions: This study revealed the association between the use of hair products and the concentration of urine benzophenone-3 in the general Korean population.

Relationship between crustacean consumption and serum perfluoroalkyl substances (PFAS): the Korean National Environmental Health Survey (KoNEHS) cycle 4.

Background: Perfluoroalkyl substances (PFASs) are non-aromatic organic compounds, whose hydrogen atoms in the carbon chain substituted by fluorine atoms. PFASs exhibit developmental toxicity, carcinogenicity, hepatotoxicity, reproductive toxicity, immunotoxicity, and hormone toxicity. PFASs are used in the production of disposable food packages, aircraft and automobile devices, cooking utensils, outdoor gear, furniture and carpets, aqueous film forming foam (AFFF), cables and wires, electronics, and semiconductors. This study aimed to determine the association between crustacean consumption and serum PFASs. Methods: Adult participants (2,993) aged ≥ 19 years were extracted from the 4th cycle data of the Korean National Environmental Health Survey (KoNEHS). Based on the 50th percentile concentrations of serum PFASs, participants were divided into the low-concentration group (LC) and the high-concentration group (HC). General characteristics, dietary factors, coated product usage, and personal care product usage, an independent t-test and χ2 test were analyzed. The odds ratio (OR) of serum PFAS concentration against crustacean consumption was estimated via logistic regression analysis adjusting for general characteristics, dietary factors, coated product usage, and personal care product usage. Results: The OR for the HC of serum PFASs was higher in individuals with ≥once a week crustacean consumption than in those with < once a week crustacean consumption. Estimated ORs were perfluorohexanesulfonic acid 2.15 (95% confidence interval [CI]: 1.53-3.02), perfluorononanoic acid (PFNA) 1.23 (95% CI: 1.07-1.41), and perfluorodecanoic acid (PFDeA) 1.42 (95% CI: 1.17-1.74) in males, and perfluorooctanoic acid 1.48 (95% CI: 1.19-1.84), perfluorooctanesulfonic acid 1.39 (95% CI: 1.27-1.52), PFNA 1.70 (95% CI: 1.29-2.26) and PFDeA 1.43 (95% CI: 1.32-1.54) in females. Conclusions: This study revealed the association between the crustacean consumption and concentrations of serum PFASs in general Korean population.

Spatial Control of Nickel Vacancies in Colloidal NiMgO Nanocrystals for Efficient and Stable All-inorganic Quantum Dot Light-Emitting Diodes.

Colloidal quantum dot (QD)-based light-emitting diodes (QD-LEDs) have reached the pinnacle of quantum efficiency and are now being actively developed for next-generation displays and brighter light sources. Previous research has suggested utilizing inorganic hole-transport layers (HTLs) to explore brighter and more stable QD-LEDs. However, the performance metrics of such QD-LEDs with inorganic HTLs generally lag behind those of organic-inorganic hybrid QD-LEDs employing organic HTLs. In this study, colloidal NiMgO nanocrystals (NCs) with spatially controlled Mg are introduced as HTLs for realizing efficient and stable all-inorganic QD-LEDs. During the co-condensation of Ni and Mg precursors to produce valence band-lowered NiMgO NCs, incorporating ≈2% Mg into the NiO lattice creates additional Ni vacancies (VNi) within and on the NCs, influencing the hole concentration and mobility of the NiMgO NC films. Passivating the VNi exposed on the surface with magnesium hydroxide allows for tuning the electrical properties of the NiMgO NCs relative to those of an electron transport layer, allowing for a balanced charge supply and suppressed negative charging of the QDs. Optimized all-inorganic QD-LEDs employing NiMgO NCs achieved a peak external quantum efficiency of 16.4%, peak luminance of 269 455 cd m⁻2, and a half-life of 462 690 h at 100 nit.

Relationship between the use of plastics in refrigerator food storage and urine phthalate metabolites: the Korean National Environmental Health Survey (KoNEHS) cycle 3.

Background: Plastics are high-molecular-weight materials composed of long carbon chains. They are prevalent in daily life, present in various items such as food containers and microwavable packaging. Phthalates, an additive used to enhance their flexibility, are endocrine-disrupting chemicals. We utilized the data from the Korean National Environmental Health Survey (KoNEHS) cycle 3, representing the general South Korean population, to investigate the relationship between the use of plastics in refrigerator food storage and phthalate exposure. Methods: We assessed 3,333 adult participants (aged ≥ 19 years) including 1,526 men and 1,807 women, using data from KoNEHS cycle 3. Using the 75th percentile concentration, urine phthalate metabolites were categorized into high and low-concentration groups. χ2 test was conducted to analyze variations in the distribution of each variable, considering sociodemographic factors, health-related factors, food intake, the use of plastics, and the concentration of urine phthalate metabolites as the variables. To calculate odds ratios (ORs) for the high-concentration group of urine phthalate metabolites based on the use of plastics in refrigerator food storage, logistic regression analysis was conducted. Results: In men, the use of plastics in refrigerator food storage had significantly higher adjusted ORs compared to those using the others. The adjusted ORs were calculated as follows: mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) had an OR of 1.35 (95% confidence interval [CI]: 1.05-1.72), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) had an OR of 1.48 (95% CI: 1.16-1.88), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP) had an OR of 1.32 (95% CI: 1.04-1.66), ∑di(2-ethylhexyl) phthalate (∑DEHP) had an OR of 1.37 (95% CI: 1.08-1.74) and mono-n-butyl phthalate (MnBP) had an OR of 1.44 (95% CI: 1.13-1.84). Conclusion: The concentrations of urine phthalate metabolites (MEHHP, MEOHP, MECPP, ∑DEHP, and MnBP) were significantly higher in men who used plastics in refrigerator food storage compared to those using the others.

Relationship between visual display terminal working hours and headache/eyestrain in Korean wage workers during the COVID-19 pandemic: the sixth Korean Working Conditions Survey.

Background: Prolonged use of visual display terminal (VDT) can cause eyestrain, dry eyes, blurred vision, double vision, headache and musculoskeletal symptoms (neck, shoulder, and wrist pain). VDT working hours among workers have greatly increased during the coronavirus disease 2019 (COVID-19) pandemic. Therefore, this study aimed to investigate the relationship between VDT working hours and headache/eyestrain in wage workers using data from the sixth Korean Working Conditions Survey (KWCS) (2020-2021) conducted during the COVID-19 pandemic. Methods: We analyzed the sixth KWCS data of 28,442 wage workers aged 15 years or older. The headache/eyestrain that occurred in the last year was assessed. The VDT work group included workers who use VDT always, almost always, and three-fourth of the working hours, while the non-VDT work group included workers who use VDT half of the working hours, one-fourth of the working hours, almost never, and never. To analyze the relationship between VDT working hours and headache/eyestrain, the odds ratios (ORs) and 95% confidence interval (CI) were calculated using logistic regression analysis. Results: Among the non-VDT work group, 14.4% workers experienced headache/eyestrain, whereas 27.5% workers of the VDT work group experienced these symptoms. For headache/eyestrain, the VDT work group showed adjusted OR of 1.94 (95% CI: 1.80-2.09), compared with the non-VDT work group, and the group that always used VDT showed adjusted OR of 2.54 (95% CI: 2.26-2.86), compared with the group that never used VDT. Conclusions: This study suggests that during the COVID-19 pandemic, as VDT working hours increased, the risk of headache/eyestrain increased for Korean wage workers.

Relationship between shellfish consumption and urinary phthalate metabolites: Korean National Environmental Health Survey (KoNEHS) cycle 3 (2015-2017).

Background: Phthalates are endocrine disrupting chemicals that are widely used in the production of items of daily life such as in polyvinylchloride plastics, insecticides, and medical devices. This study aimed to determine the association between phthalate exposure and shellfish consumption using data from the Korean National Environmental Health Survey (KoNEHS) cycle 3 (2015-2017), which is a nationally representative survey. Methods: In this study, we analyzed the KoNEHS cycle 3 data of 3,333 (1,526 men and 1,807 women) adults aged more than 19 years. Data related to the variables of sociodemographic factors, health-related behaviors, dietary factors, seafood consumption frequency, and urinary phthalate metabolites concentrations were collected. The concentrations of urinary phthalate metabolites of all the participants were divided into quartiles to define high and low concentration groups based on the 75th percentile concentration. A χ2 test was conducted to analyze the distribution of independent variables. To analyze the relationship between shellfish consumption and phthalate exposure, the odds ratios (ORs) were calculated using logistic regression analysis. Results: Total adults with shellfish consumption frequency of over once a week showed the following adjusted ORs for high concentrations of the following metabolites compared with the group that consumed shellfish once a week or less: 1.43 (95% confidence interval [CI]: 1.01-2.06) for mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), 1.43 (95% CI: 1.01-2.03) for mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), 1.57 (95% CI: 1.10-2.24) for ∑di-2-ethylhexyl phthalate (∑DEHP), 2.01 (95% CI: 1.46-2.77) for mono-carboxyoctyl phthalate (MCOP), 1.56 (95% CI: 1.11-2.18) for mono-carboxy-isononly phthalate (MCNP), and 2.57 (95% CI: 1.85-3.56) for mono (3-carboxypropyl) phthalate (MCPP). Conclusions: The concentrations of urinary phthalate metabolites (MEOHP, MECPP, ∑DEHP, MCOP, MCNP, and MCPP) were higher in adults with a higher frequency of shellfish consumption.

Single-step formation of a graphene-metal hybrid transparent and electrically conductive film.

We report here a rapid (10 s of heating) graphene growth method that can be carried out on any desired substrate, including an insulator, thus negating the need for the transfer from the metal substrate. This technique is based on metal-induced crystallization of amorphous carbon (a-C) to graphene, and involves an ultra-thin metal layer that is less than 10 nm in thickness. Rapid annealing of a bilayer of a-C and metal deposited on the surface leads to the formation of graphene film, and to subsequent breaking-up of the thin metal layer underneath the film, thus resulting in the formation of a graphene­metal hybrid film which is both transparent and electrically conducting. Based on Raman studies, we have also systematically compared ultra-thin metal-induced crystallization behavior with a case of conventional thick metal. Based on the present investigation, it was observed that the dominant growth mechanism in ultra-thin metal-induced crystallization is nucleation controlled.

Electrocardiogram abnormalities in antimony exposed workers in the automotive brake lining manufacturing industry: a case report.

Background: Antimony is used in catalysts, pesticides, brake systems, pharmaceuticals, and synthetic fire retardants in the plastic, paint, and rubber industries. Accumulation of trivalent antimony compounds in the body can cause cardiotoxic effects and increase the risk of electrocardiogram (ECG) abnormalities and sudden death. Antimony exposure can result in action potential prolongation, causing a cardiac repolarization delay, which appears as QTc prolongation and T-wave abnormalities on the ECG. There are no studies on antimony-associated cardiac toxicity in Korea. Case presentation: Accordingly, the present study reports cases of ECG abnormalities in workers handling antimony trisulfide at a company located in the Gyeongsangbuk-do region. Nineteen workers employed at an automobile brake lining manufacturer were exposed to antimony trisulfide dust through thermoforming, grinding, and drilling processes. In 2020, the workers were reported to work 12-hour shifts, 5 days a week. The time-weighted average (TWA) of antimony trisulfide exposure measured in workers was 0.0028 mg/m3. Two workers were excluded from the analysis due to pre-existing medical conditions (cardiovascular disease). Of the remaining 17 workers, ECG abnormalities were found in 41% (seven out of 17: four with QTc prolongation and T-wave abnormalities; two with only T-wave abnormalities; and one with only QTc prolongation). Conclusions: This case report outlines the first few cases in Korea in which potential cardiac toxicity caused by occupational exposure to antimony was identified. However, data regarding cardiac toxicity caused by antimony exposure are still lacking in Korea; thus, additional studies are needed to identify causal relationships.

Relationship between shift work and age-related macular degeneration: a cross-sectional analysis of data from the 5th Korea National Health and Nutrition Examination Survey (2010-2012).

BACKGROUND: Age-related macular degeneration (AMD) is the leading cause of blindness. Shift work has well-known adverse effects on health. However, few studies have investigated the relationship between shift work and AMD. This study was conducted to investigate the relationship between shift work and AMD. METHODS: This study used aggregated data from the 2010-2012 cycles of the Korea National Health and Nutrition Examination Survey. The work schedules were classified into 2 types: day work and shift work. AMD was determined using fundus photographs. The χ2 test and multiple logistic regression analysis were used to assess sex-stratified relationship between shift work and AMD. RESULTS: The odds ratio (OR) of AMD in male shift workers was higher (1.54 [95% confidence interval, CI: 1.01-2.36]) than that in male day workers after adjusting for covariates. After dividing into subgroups of the shift work pattern, the OR of AMD in male night shift workers was higher (1.75 [95% CI: 1.07-2.85]) than that in male day workers after adjusting for covariates. However, results of the female worker group were not significant. CONCLUSIONS: The results of this study provide limited support for the hypothesis that shift work is related to AMD. Further prospective studies are needed to define the relationship between shift work and AMD.

High-Resolution Colloidal Quantum Dot Film Photolithography via Atomic Layer Deposition of ZnO.

High-resolution patterning of quantum dot (QD) films is one of the preconditions for the practical use of QD-based emissive display platforms. Recently, inkjet printing and transfer printing have been actively developed; however, high-resolution patterning is still limited owing to nozzle-clogging issues and coffee ring effects during the inkjet printing and kinetic parameters such as pickup and peeling speed during the transfer process. Consequently, employing direct optical lithography would be highly beneficial owing to its well-established process in the semiconductor industry; however, exposing the photoresist (PR) on top of the QD film deteriorates the QD film underneath. This is because a majority of the solvents for PR easily dissolve the pre-existing QD films. In this study, we present a conventional optical lithography process to obtain solvent resistance by reacting the QD film surface with diethylzinc (DEZ) precursors using atomic layer deposition. It was confirmed that, by reacting the QD surface with DEZ and coating PR directly on top of the QD film, a typical photolithography process can be performed to generate a red/green/blue pixel of 3000 ppi or more. QD electroluminescence devices were fabricated with all primary colors of QDs; moreover, compared to reference QD-LED devices, the patterned QD-LED devices exhibited enhanced brightness and efficiency.

Bragg-Berry flat reflectors for transparent computer-generated holograms and waveguide holography with visible color playback capability.

Various approaches are being pursued to realize compact optical elements with the ability to manipulate light, but it is difficult to simultaneously achieve high reflectivity and the ability to see through the element. Here, we present a reflective computer-generated hologram that is completely transparent in the visible, based on the Berry (geometric) phase in a self-organizing Bragg reflector. The Bragg reflector has a helical dielectric tensor distribution with the phase information imprinted in the distribution of the optic axis on the substrate. The structure possesses only a single Fourier component and high-order reflections are suppressed; thus, the device appears completely transparent by setting the main reflection band outside the visible range for all angles of incidence accessible by ambient light. On the other hand, the encoded phase information can be played back using visible light by increasing the accessible incidence angle, which we demonstrate experimentally by (i) attaching a coupling prism, and (ii) integrating the device in a waveguide. Bragg-Berry reflectors thus enable a new route to realize advanced optical elements with no apparent reflection in the visible region.

Association of work-life balance with occupational injury and work-related musculoskeletal pain among Korean workers.

BACKGROUND: The concept of work-life balance (WLB) has become an important issue in workers' health and safety. This study aims to investigate the relationship between WLB and occupational injury and work-related musculoskeletal pain. METHOD: The study included 27,383 workers who participated in the Fifth Korean Working Conditions Survey. Participants were divided into good WLB and poor WLB groups based on their responses to the five question items which comprised two dimensions: work-on-life conflict (items, 1-3) and life-on-work conflict (items 4 and 5). Occupational injury and musculoskeletal pain were also assessed using the question items. The χ2 test and multivariate logistic regression analyses were performed to examine the relationship of WLB to occupational injury and musculoskeletal pain while considering socio-demographic and occupational characteristics and ergonomic and psychological risk factors. RESULTS: Of the 27,383 participants, 252 (0.9%) had experienced an occupational injury and 6,408 (23.4%) had musculoskeletal pain. The poor WLB group had higher injury rates for both men (1.7%) and women (0.9%) than the good WLB group (1.1% and 0.4%, respectively). Additionally, the prevalence of musculoskeletal pain was higher for both men and women in the poor WLB group (25.2% and 28.0%, respectively) than for men and women in the good WLB group (18.7% and 23.6%, respectively). In the logistic regression analysis, the adjusted odds ratio of WLB for occupational injury was 1.37 (95% confidence interval [CI]: 1.06-1.78), and that for musculoskeletal pain was 1.14 (95% CI: 1.07-1.21), showing positive associations of WLB with both occupational injury and musculoskeletal pain. CONCLUSIONS: Poor WLB causes an increase in occupational injury and musculoskeletal pain. Therefore, an improvement in WLB may reduce the incidence of occupational injury and musculoskeletal pain among workers. Social and policy-related initiatives are needed to improve workers' WLB to reduce occupational injury and musculoskeletal pain.

Comparison of Growth Behavior and Electrical Properties of Graphene Grown on Solid and Liquid Copper by Chemical Vapor Deposition.

We study the graphene growth behavior above and below the copper (Cu) melting point (1083 °C) by only changing the growth temperature from 1020 °C to 1100 °C at intervals of 40 °C, to investigate the effect of the Cu phase as a catalyst layer in graphene growth. We investigate the graphene growth behavior by observing the changes in nucleation density and grain size with growth time. As the phase of the Cu catalyst changes from solid to liquid, the grain size of graphene increases by 2 orders of magnitude from 0.4 to 40 µm, while the nuclei density decreases by 4 orders of magnitude from 3.02/µm2 to 0.0004/µm2. Additionally, as in previous studies, graphene growth shows a well-aligned hexagonal shape on liquid Cu although graphene on solid Cu shows an irregular shape under the same growth conditions. The effect of the smooth surface of the liquid metal catalyst on graphene growth is remarkable even after considering the temperature difference. The reduction of defect density arising from the increase of the graphene grain size is confirmed by Raman spectroscopy. Additionally, the improvement in electrical properties is also investigated by Hall measurements.

Sheet Resistance Analysis of Interface-Engineered Multilayer Graphene: Mobility Versus Sheet Carrier Concentration.

Both interlayer-undoped and interlayer-doped multilayer graphenes were prepared by the multiple transfers of graphene layers with multiple Cu etching (either dopant-free or doped during etching) and transfer, and the effect of interface properties on the electrical properties of multilayer graphene was investigated by varying the number of layers from 1 to 12. In both the cases, the sheet resistance decreased with increasing number of layers from 700 to 104 Ω/sq for the interlayer-undoped graphene and from 280 to 25 Ω/sq for the interlayer-doped graphene. Further, Hall measurements revealed that the origins of the sheet resistance reduction in the two cases are different. In the interlayer-undoped graphene, the sheet resistance decreased because of the increase in mobility with the addition of inner layers, which has a low carrier density and a high carrier mobility. On the other hand, it decreased because of the increase in sheet carrier density in the interlayer-doped multilayer graphene. The mobility and carrier density variations in both the cases were confirmed by fitting with the model of Hall effect in the heterojunction. In addition, we found that surface property modification by the doping of the top layer and the formation of double-layer graphene with different partial coverages allow the separate control of carrier density and mobility. Our study provides an effective approach for controlling the properties of multilayer graphene for electronic applications.

Selective Atomic Layer Deposition of Metals on Graphene for Transparent Conducting Electrode Application.

Although graphene has considerable potential as a next-generation transparent conducting electrode (TCE) material owing to its excellent optical transparency and flexibility, its electrical properties require further improvement for industrial application. This study reports a pathway of doping graphene by selective atomic layer deposition (ALD) of metals to elevate the electrical conductivity of graphene. Introduction of a novel Pt precursor [dimethyl(N,N-dimethyl-3-butene-1-amine-N)platinum(II); C8H19NPt; DDAP] facilitates a low-temperature (165 °C) process. The sheet resistance (Rs) of graphene is reduced significantly from 471 to 86.8 Ω sq-1 after 200 cycles of Pt ALD, while the optical transmittance at 550 nm (T) is maintained above 90% up to 200 cycles due to the selective growth of Pt on the defects of graphene. Furthermore, comprehensive analysis, including metal (Ru, Pt, and Ni) ALD on graphene, metal (Ru, Pt, Ni, Au, and Co) evaporation on graphene, and change in the ALD chemicals, demonstrates that ALD allows efficient graphene doping and the oxygen affinity of the metal is one of the key properties for efficient graphene doping. Finally, Pt ALD is applied to a multilayer graphene to further reduce Rs down to 75.8 Ω sq-1 yet to be highly transparent (T: 87.3%) after 200 cycles. In summary, the selective ALD of metals opens a way of improving the electrical properties of graphene to a level required for the industrial TCE application and has the potential to promote development of other types of functional metal-graphene composites.

Difference in health status of Korean farmers according to gender.

BACKGROUND: The objective of this study was to compare differences in lifestyle diseases, musculoskeletal pain, psychosocial stress, and self-health awareness according to gender in Korean farmers. METHODS: The study population comprised 436 farmers residing in rural areas in Korea. A self-administered questionnaire was used to survey demographic characteristics, health-related behaviors, and musculoskeletal pain. The psychosocial well-being index short form (PWI-SF) was used to survey psychosocial stress, and the 12-item short form health survey (SF-12) was used to survey self-health awareness. In addition, a clinical examination was performed for each participant, and lifestyle diseases were identified through a health checkup. RESULTS: Among lifestyle diseases, females showed a significantly higher proportion than males for metabolic syndrome (OR: 4.57 [95% CI, 1.67-12.51]). For musculoskeletal pain, females again showed significantly higher proportion than males for hand pain (OR: 16.79 [95% CI, 3.09-91.30]), and pain in at least one body part (OR: 2.34 [95% CI, 1.16-4.70]). For psychosocial stress, females showed a significantly higher proportion than males for high-risk stress (OR: 3.10 [95% CI, 1.17-8.24]). Among the items in self-health awareness, females showed significantly higher proportion than males for mental component score (MCS) (OR: 3.10 [95% CI, 1.52-6.31]) and total score (OR: 2.34 [95% CI, 1.11-4.90]). CONCLUSIONS: For all items that showed significant differences, females showed higher proportion than males, which indicates that female farmers tended to have poorer overall health than male farmers. Therefore, specialized programs will have to be developed to improve the health of female farmers.

Influence of indium-tin-oxide and emitting-layer thicknesses on light outcoupling of perovskite light-emitting diodes.

Metal halide perovskite light-emitting diodes (PeLEDs) are emerging as a promising candidate for next-generation optoelectronic devices. The efficiency of PeLEDs has developed explosively in a short time, but their overall efficiency is still low. This is strongly related to the high refractive indexes of indium-tin-oxide (ITO) and perovskite emitting layers. Various outcoupling strategies are being introduced to outcouple the light trapped inside the layers. However, the proposed methods have experimental challenges that need to be overcome for application to large-area electronics. Based on optical simulations, we demonstrate that the thicknesses of the ITO and perovskite layers are key parameters to improve the outcoupling efficiency of PeLEDs. In addition, the optical energy losses of PeLEDs can be reduced significantly by properly adjusting the thicknesses of the two layers. This leads to outstanding optical performance with a maximum EQE greater than 20% without using any other external outcoupling strategies.