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Capacitors based on ABO3-type perovskite oxides show considerable promise for overcoming the limitations of nanoscale integration for dynamic random access memory (DRAM) devices. Among thermodynamically stable perovskite oxides, titanates (ATiO3) exhibit high dielectric permittivity in metal–insulator–metal (MIM) configurations. However, their ultimate properties remain under scrutiny for mitigating the large leakage current caused by their narrow bandgap (3 eV). Herein, substantially enhanced dielectric properties of an epitaxial SrRuO3/Ba0.5Sr0.5TiO3/SrRuO3 MIM capacitor with a thin dielectric layer (10 nm) are reported. The dielectric/electrode heterointerface was engineered to realize a capacitor with low leakage current and high dielectric permittivity. A pit-free and stoichiometric SrRuO3 bottom electrode with atomically smooth surface was exploited for suppressing defect formation at the heterointerface. The critical roles of oxygen vacancies and substituted transition-metal atoms in determining the leakage current were accessed and a strategy for reducing the leakage current via interface engineering was established. Consequently, a dielectric permittivity of 861 and leakage current density of 5.15 × 10− 6 A/cm2 at 1 V were obtained with the thinnest dielectric layer ever reported. Our work paves the way for the development of perovskite-oxide-based capacitors in next-generation DRAM memories.

Background Variations by hospital and region in the selection of an early invasive strategy (EIS) after non–ST-segment elevation myocardial infarction (NSTEMI) in patients with high-risk criteria are unknown. Methods We evaluated the data of 7037 patients with NSTEMI from 20 hospitals of 3 regions from the Korean Acute Myocardial Infarction Registry–National Institute of Health database. We used hierarchical generalized linear mixed-models to estimate region- and hospital-level variation in the selection of an EIS after adjusting for patient-level high-risk criteria. We explored the variation using the median rate ratio (MRR), which estimates the relative difference in the risk ratios of two hypothetically identical patients at two different sites. Results An EIS was selected in 84.4% of patients. At the hospital level, the median selection rate was 80.4%. At the region level, the median selection rate was 74.9% in the east region, 81.3% in the north region, and 83.9% in the west region, respectively. After adjusting for patient-level covariates, we found significant hospital- (MRR 2.19, 95% confidence interval [CI]: 1.74–3.03) and region-level (MRR 1.88, 95%CI: 1.26–5.44) variation in the selection of an EIS. Among patient-level factors, male sex, ongoing chest pain, history of coronary artery disease or acute heart failure, and GRACE risk score > 140 were independently associated with the selection of an EIS. Conclusions We observed significant hospital- and region-level variation in the selection of an EIS after NSTEMI in high-risk patients. Quality improvement efforts are required to standardize decision making and to improve clinical outcomes.

We investigated if elevated cardiac troponin I (cTnI) serum levels before non-cardiac surgery were predictors of postoperative cardiac events in patients with end stage renal disease (ESRD) undergoing dialysis. In total, 703 consecutive patients with ESRD undergoing dialysis who underwent non-cardiac surgery were enrolled. Preoperative cTnI serum levels were measured at least once in all patients. The primary endpoint was defined as a composite of cardiac death, myocardial infarction (MI), and pulmonary edema during hospitalization or within 30 days after surgery in patients with a hospitalization longer than 30 days after surgery. Postoperative cardiac events occurred in 48 (6.8%) out of 703 patients (cardiac death 1, MI 18, and pulmonary edema 33). Diabetes mellitus (DM), previous ischemic heart disease, and congestive heart failure were more common in patients with postoperative cardiac events. Peak cTnI serum levels were higher in patients with postoperative cardiac event (180 ± 420 ng/L vs. 80 ± 190 ng/L, p = 0.008), and also elevated peak cTnI levels > 45 ng/L were more common in patients with postoperative cardiac events (66.8% vs. 30.5%, p p = 0.017) and serum peak cTnI levels ≥ 45 ng/L (OR 3.167, 95% CI 1.557–6.444, p = 0.001) were independent predictors for the primary outcome of cardiac death/MI/pulmonary edema. Moreover, cTnI levels ≥ 45 ng/L had an incremental prognostic value to the revised cardiac risk index (RCRI) (Chi-square = 23, p p = 0.001). Elevated preoperative cTnI levels are predictors of postoperative cardiac events including cardiac death, MI, and pulmonary edema in patients with ESRD undergoing non-cardiac surgery.

Background: This study aimed to investigate the incidences of and risk factors for perioperative events following anticoagulant discontinuation in patients with non-valvular atrial fibrillation (NVAF) undergoing non-cardiac surgery. Methods: A total of 216 consecutive patients who underwent cardiac consultation for suspending perioperative anticoagulants were enrolled. A perioperative event was defined as a composite of thromboembolism and major bleeding. Results: The mean anticoagulant discontinuation duration was 5.7 (±4.2) days and was significantly longer in the warfarin group (p

With the scaling down of complementary metal–oxide semiconductors (CMOS), atomic layer deposition of high-quality HfO2 has emerged as a key technology for ultrathin and high-k gate dielectrics. Recently, heteroleptic ligand structures have been introduced to complement the limitations of existing homoleptic precursors. Among the heteroleptic precursors, partial substitution with cyclopentadiene (Cp)-based ligands has been employed for controlling the volatility and thermal stability of precursors. In this study, we investigated the effects of the Cp ligand on the high-k properties of ALD HfO2 by comparing Hf(N(CH3)2)4 and CpHf(N(CH3)2)3 through theoretical and experimental methods. We theoretically predicted the changes in precursor behavior on the surface due to the Cp ligand, such as the high activation energy for the final chemisorption and the steric hindrance caused by the bulky Cp ligand. Additionally, we experimentally found that these changes affect not only the growth rate of ALD HfO2 but also the film properties. The Cp ligand on the surface sterically hinders the reaction of the nearby OH group with precursor molecules, retaining the residual OH content in the films. Consequently, the high OH content in the films degrades the film density and leakage current of ALD HfO2 as a high-k film.

It has been known that the fear of contagion during the coronavirus disease 2019 (COVID-19) creates time delays with subsequent impact on mortality in patients with acute myocardial infarction (AMI). However, difference of time delay and clinical outcome in patients with ST-segment elevation myocardial infarction (STEMI) or non-STEMI between the COVID-19 pandemic and pre-pandemic era has not been fully investigated yet in Korea. The aim of this study was to investigate the impact of COVID-19 pandemic on time delays and clinical outcome in patients with STEMI or non-STEMI compared to the same period years prior.A total of 598 patients with STEMI (n = 195) or non-STEMI (n = 403) who underwent coronary angiography during the COVID-19 pandemic (February 1 to April 30, 2020) and pre-pandemic era (February 1 to April 30, 2017, 2018, and 2019) were analyzed in this study. Main outcomes were the incidence of time delay, cardiac arrest, and in-hospital death.There was 13.5% reduction in the number of patients hospitalized with AMI during the pandemic compared to pre-pandemic era. In patients with STEMI, door to balloon time tended to be longer during the pandemic compared to pre-pandemic era (55.7 ± 12.6 minutes vs. 60.8 ± 13.0 minutes,During the COVID-19 pandemic, there has been a considerable reduction in hospital admissions for AMI, time delay, and underuse of ACE-I/ARBs for the management of AMI, and this might be closely associated with the excess death in Korea.

The real-world emission factors of gaseous and particulate air pollutants emitted from in-use vehicles, can be rapidly estimated using monitoring data of their concentration profiles from inside roadway tunnels using a mobile laboratory equipped with fast monitoring instruments. The concentrations of CO2 and particle-bound polycyclic aromatic hydrocarbons (PM-PAHs) and NOx, were observed to increase linearly with traveling distance inside two successive roadway tunnels: the Hongjimun Tunnel and the Jeongneung Tunnel on the Naebu Express Way in Seoul, Korea, except for a small region of decrease. In the decreasing regions, within a few hundred meters of the entrance and before the exit, outside background air with low concentrations of air pollutants was thought to have intruded. From the slopes of the linear regression between distance and concentrations, a fleet-averaged (light-, medium-, and heavy-duty vehicles with 54%, 36%, and 10%, respectively) emission factor of CO2, PM-PAHs, and NOx at an average speed of ~60 km h−1 could be calculated as 197 ± 38 g km−1, 4.2 ± 0.8 × 10−4 g km−1, and 0.530 ± 0.230 g km−1, respectively, which are within the ranges of values reported in the literature. For each tunnel, the emission factors of CO2, PM-PAHs, and NOx estimated on days with higher-than-normal fractions of heavy-duty vehicles, were higher than those on other days. From these results, the new fast method proposed in this study is considered useful for estimating real-world emission factors of air pollutants by using a mobile laboratory as a complementary tool to traditional tunnel studies. This method can be used to rapidly make emission maps at roadway tunnels in mega-cities like Seoul, Korea, for urban air-quality management.

Tin oxide (SnOx) is a promising oxide semiconductor due to the distinct properties of n-type SnO2 and p-type SnO based on its stoichiometry. However, the stoichiometry control of SnOx remains challenging due to the thermodynamic instability of SnO. In the study, we focus on establishing the controllable stoichiometry of SnOx via atomic layer deposition (ALD) and subsequent treatment. The controllable synthesis of SnO2 and SnO is investigated by multiple analyses involving the chemical composition, crystal structure, and band structure. The ALD SnOx is composed mostly of Sn4+ O bonds with intrinsic oxygen vacancies and is transformed into crystalline SnO2 phase via post-annealing. The refractive index (~1.8) and optical bandgap energy (~3.6 eV) of ALD SnOx correspond to those of SnO2. Post-deposition treatment with H2 plasma enables the effective transformation of SnO2 into SnO due to the easy penetration of H+ ion into the film and de-bonding of Sn O via ion bombardment. The transformed SnO exhibits a significant amount of Sn2+ O bonds with a refractive index of 2.8 and optical bandgap energy of ~2.9 eV. Specifically, the transformed SnO exhibits promise as an oxide semiconductor because it exhibits excellent stability with respect to re-oxidation into SnO2 or further reduction into Sn metal. The present study advances practical applications that require a stable p-n junction through n-type SnO2 and p-type SnO in various forms of device architectures.

Background It is difficult to evaluate the risk of patients with severe renal dysfunction before surgery due to various limitations despite high postoperative cardiac events. This study aimed to investigate the value of a newly reclassified Revised Cardiac Risk Index (RCRI) that incorporates QRS fragmentation (fQRS) as a predictor of postoperative cardiac events in patients with severe renal dysfunction. Methods Among the patients with severe renal dysfunction, 256 consecutive patients who underwent both a nuclear stress test and noncardiac surgery were evaluated. We reclassified RCRI as fragmented RCRI (FRCRI) by integrating fQRS on electrocardiography. We defined postoperative major adverse cardiac event (MACE) as a composite of cardiac death, nonfatal myocardial infarction, and pulmonary edema. Results Twenty-eight patients (10.9%) developed postoperative MACE, and this was significantly frequent in patients with myocardial perfusion defect (41.4% vs. 28.0%, p = 0.031). fQRS was observed 84 (32.8%) patients, and it was proven to be an independent predictor of postoperative MACE after adjusting for the RCRI (odds ratio 3.279, 95% confidence interval (CI) 1.419–7.580, p = 0.005). Moreover, fQRS had an incremental prognostic value for the RCRI (chi-square = 7.8, p = 0.005), and to the combination of RCRI and age (chi-square = 9.1, p = 0.003). The area under curve for predicting postoperative MACE significantly increased from 0.612 for RCRI to 0.667 for FRCRI (p = 0.027) and 23 patients (32.4%) originally classified as RCRI 2 were reclassified as FRCRI 3. Conclusions A newly reclassified FRCRI that incorporates fQRS, is a valuable predictor of postoperative MACE in patients with severe renal dysfunction undergoing noncardiac surgery.

Graphical abstract, Background In the potent new antiplatelet era, it is important issue how to balance the ischemic risk and the bleeding risk. However, previous risk models have been developed separately for in-hospital mortality and major bleeding risk. Therefore, we aimed to develop and validate a novel combined model to predict the combined risk of in-hospital mortality and major bleeding at the same time for initial decision making in patients with acute myocardial infarction (AMI). Methods Variables from the Korean Acute Myocardial Infarction Registry (KAMIR) – National Institute of Health (NIH) database were used to derive (n = 8955) and validate (n = 3838) a multivariate logistic regression model. Major adverse cardiovascular events (MACEs) were defined as in-hospital death and major bleeding. Results Seven factors were associated with MACE in the model: age, Killip class, systolic blood pressure, heart rate, serum glucose, glomerular filtration rate, and initial diagnosis. The risk model discriminated well in the derivation (c-static = 0.80) and validation (c-static = 0.80) cohorts. The KAMIR-NIH risk score was developed from the model and corresponded well with observed MACEs: very low risk (0.9%), low risk (1.7%), moderate risk (4.2%), high risk (8.6%), and very high risk (23.3%). In patients with MACEs, a KAMIR-NIH risk score ≤ 10 was associated with high bleeding risk, whereas a KAMIR-NIH risk score > 10 was associated with high in-hospital mortality. Conclusion The KAMIR-NIH in-hospital MACEs model using baseline variables stratifies comprehensive risk for in-hospital mortality and major bleeding, and is useful for guiding initial decision making.

Background Data regarding the association between preexisting cardiovascular risk factors (CVRFs) and cardiovascular diseases (CVDs) and the outcomes of patients requiring hospitalization for coronavirus disease 2019 (COVID-19) are limited. Therefore, the aim of this study was to investigate the impact of preexisting CVRFs or CVDs on the outcomes of patients with COVID-19 hospitalized in a Korean healthcare system. Methods Patients with COVID-19 admitted to 10 hospitals in Daegu Metropolitan City, Korea, were examined. All sequentially hospitalized patients between February 15, 2020, and April 24, 2020, were enrolled in this study. All patients were confirmed to have COVID-19 based on the positive results on the polymerase chain reaction testing of nasopharyngeal samples. Clinical outcomes during hospitalization, such as requiring intensive care and invasive mechanical ventilation (MV) and death, were evaluated. Moreover, data on baseline comorbidities such as a history of diabetes, hypertension, dyslipidemia, current smoking, heart failure, coronary artery disease, cerebrovascular accidents, and other chronic cardiac diseases were obtained. Results Of all the patients enrolled, 954 (42.0%) had preexisting CVRFs or CVDs. Among the CVRFs, the most common were hypertension (28.8%) and diabetes mellitus (17.0%). The prevalence rates of preexisting CVRFs or CVDs increased with age (P < 0.001). The number of patients requiring intensive care (P < 0.001) and invasive MV (P < 0.001) increased with age. The in-hospital death rate increased with age (P < 0.001). Patients requiring intensive care (5.3% vs. 1.6%; P < 0.001) and invasive MV (4.3% vs. 1.7%; P < 0.001) were significantly greater in patients with preexisting CVRFs or CVDs. In-hospital mortality (12.9% vs. 3.1%; P < 0.001) was significantly higher in patients with preexisting CVRFs or CVDs. Among the CVRFs, diabetes mellitus and hypertension were associated with increased requirement of intensive care and invasive MV and in-hospital death. Among the known CVDs, coronary artery disease and congestive heart failure were associated with invasive MV and in-hospital death. In multivariate analysis, preexisting CVRFs or CVDs (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.07–3.01; P = 0.027) were independent predictors of in-hospital death after adjusting for confounding variables. Among individual preexisting CVRF or CVD components, diabetes mellitus (OR, 2.43; 95% CI, 1.51–3.90; P < 0.001) and congestive heart failure (OR, 2.43; 95% CI, 1.06–5.87; P = 0.049) were independent predictors of in-hospital death. Conclusion Based on the findings of this study, the patients with confirmed COVID-19 with preexisting CVRFs or CVDs had worse clinical outcomes. Caution is required in dealing with these patients at triage., Graphical Abstract

There is insufficient information on the relationship between the N-terminal pro-brain natriuretic peptide (NT-proBNP) level and collateral circulation (CC) formation after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction. We analyzed 857 patients who underwent primary PCI. The serum NT-proBNP levels were measured on the day of admission, and the CC was scored according to Rentrop’s classification. Log-transformed NT-proBNP levels were significantly higher in patients with good CC compared to those with poor CC (6.13 ± 2.01 pg/mL versus 5.48 ± 1.97 pg/mL, p p p = 0.001). The incidence of left ventricular (LV) dysfunction (p p p = 0.003). The association between NT-proBNP and collateral formation was not influenced by pre-TIMI flow and LV function. NT-proBNP appears to reflect the degree of collateral formation in the early phase of STEMI and might have a new role as a useful surrogate biomarker for collateral formation in patients undergoing primary PCI.

Background This study investigates the impact of the occurrence of Osborn waves during therapeutic hypothermia (TH) on the recurrence of future fatal arrhythmias in patients resuscitated after sudden cardiac arrest (SCA). Methods Of all survivors of out-of-hospital SCA, 100 consecutive patients (mean age, 52 ± 15 years; 80% men) who received TH were included in this study. Results The most common first documented arrhythmia was ventricular fibrillation (VF) (77%), and ischemic heart disease (44%) and idiopathic VF (22%) were the most common causes of SCA in resuscitated patients. During TH, Osborn waves developed in 29 patients (29%). Osborn waves occurred more frequently in patients with Brugada syndrome. Patients with Osborn waves had lower in-hospital (10.3% vs 26.8%; P = .072) and 1-year death rates (20.7% vs 39.4%; P = .073) and better cerebral function (cerebral performance category scale, 2.0 ± 1.5 vs 2.7 ± 1.8; P = .053) than those without Osborn waves, although there was no statistical significance. Among 78 in-hospital survivors, 31 (40%) underwent implantable cardioverter-defibrillator (ICD) implantation. Appropriate ICD shocks from fatal arrhythmias were more frequent in patients who had Osborn waves than in those without Osborn waves (43% vs 6%; P = .032). Conclusions Osborn waves during TH had no significant effect on the survival and cerebral function of patients resuscitated SCA. However, appropriate ICD shocks due to the recurrence of VF were more frequent in patients with Osborn waves during long-term follow-up.

Background The association of N-terminal pro-B type natriuretic peptide (NT-proBNP) and plasma renin activity (PRA) for the prognosis of the patients with acute heart failure (HF) has not been fully investigated. This study aimed to determine the association between NT-proBNP and PRA and to investigate the incremental value of PRA to NT-proBNP for predicting long term prognosis in patients with acute HF. Methods Three hundred and ninety-six patients (mean age, 64.7 ± 15.9 years; 46.5% female) presenting with acute HF were enrolled between December 2004 and July 2013. Patients with newly diagnosed HF as well as patients with acute exacerbated chronic HF were included. The prognosis was assessed with the composite event of all-cause mortality and readmission for HF during a 2-year follow-up period. Results The etiology of HF was ischemic in 116 (29.3%) patients. In a Cox proportional hazards model, log-transformed PRA (hazard ratio [HR], 1.205; P = 0.007) was an independent predictor of the composite outcome of all-cause mortality and readmission for HF in addition to age (HR, 1.032; P = 0.001), white blood cell (WBC) count (HR, 1.103; P < 0.001), and left ventricular ejection fraction (LVEF) (HR, 0.978; P = 0.013). Adding PRA to age, sex, LVEF, and NT-proBNP significantly improved the prediction for the composite outcome of all-cause mortality and readmission for HF, as shown by the net reclassification improvement (0.47; P < 0.001) and integrated discrimination improvement (0.10; P < 0.001). Conclusion PRA could provide incremental predictive value to NT-proBNP for predicting long term prognosis in patients with acute HF., Graphical Abstract

A method for significantly increasing the growth rates (GRs) of high- k oxide thin films grown via plasma-enhanced atomic layer deposition (PE-ALD) by enhancing the plasma density through the addition of Ar gas to the O2 plasma oxidant was developed. This approach led to improvements of ∼60% in the saturation GRs of PE-ALD ZrO2, HfO2, and SiO2. Furthermore, despite the significantly higher GR enabled by PE-ALD, the mechanical and dielectric properties of the PE-ALD oxide films were similar or even superior to those of films grown via the conventional O2 plasma process. Optical emission spectroscopy analyses in conjunction with theoretical calculation of the electron energy distribution function revealed that adding Ar gas to the O2 plasma increased the density of high-energy electrons, thereby generating more O2 plasma species, such as ions and radicals, which played a key role in improving the GRs and the properties of the films. This promising approach is expected to facilitate the high-volume manufacturing of films via PE-ALD, especially for use as gate insulators in thin-film transistor-based devices in the display industry.

Enhancing the dielectric constant (k) of conventional gate dielectric materials such as HfO2 and ZrO2 is one of the important requirements for further scaling down of devices in future years. One promising approach for achieving this is to incorporate a specific element in the high-k host material for stabilizing a particular higher-k crystalline phase. Although Ge has been theoretically suggested as a stabilizer for ZrO2, there are no experimental studies correlating the structure of ZrO2 films fabricated by atomic layer deposition (ALD) with their electrical properties. In this work, we systematically investigated the structural and electrical properties of Ge-doped ZrO2 films prepared by ALD. We used germanium butoxide (Ge(OnBu)4) and Zr tris(dimethylamino)cyclopentadienyl zirconium as the Ge and Zr precursors, respectively, with O3 as a reactant. We controlled the ALD cycle ratio using a supercycle process (GeO2/ZrO2 = 1:128, 1:64, 1:32, 1:16, 1:8, 1:4, and 1:2) to produce the alloy films. Electrical properties of these samples were evaluated by measuring the electrical characteristics of metal-oxide-semiconductor (MOS) capacitors based on them, and the results are discussed together with crystallographic analysis. The results revealed that Ge incorporation into ZrO2 induced the stabilization of the cubic/tetragonal phase of the ZrO2 film at low temperatures and improved its dielectric properties. Consequently, this is a systematic and facile method to optimize the dielectric properties of Ge-doped ZrO2 prepared by varying the ALD cycle ratio, and these films could be applied in future nanoscale devices.

We report the effect of Y2O3 passivation by atomic layer deposition (ALD) using various oxidants, such as H2O, O2 plasma, and O3, on In–Ga–Zn–O thin-film transistors (IGZO TFTs). A large negative shift in the threshold voltage (Vth) was observed in the case of the TFT subjected to the H2O-ALD Y2O3 process; this shift was caused by a donor effect of negatively charged chemisorbed H2O molecules. In addition, degradation of the IGZO TFT device performance after the O2 plasma-ALD Y2O3 process (field-effect mobility (μ) = 8.7 cm2/(V·s), subthreshold swing (SS) = 0.77 V/dec, and Vth = 3.7 V) was observed, which was attributed to plasma damage on the IGZO surface adversely affecting the stability of the TFT under light illumination. In contrast, the O3-ALD Y2O3 process led to enhanced device stability under light illumination (ΔVth = −1 V after 3 h of illumination) by passivating the subgap defect states in the IGZO surface region. In addition, TFTs with a thicker IGZO film (55 nm, which was the optimum thicknes...

Dynamic random access memory (DRAM) is reaching the scaling limit owing to the requirements for a high capacitance density and low leakage current of metal–insulator–metal (MIM) capacitors. We investigated the Ta-doped ZrO2 dielectric as a novel high-k candidate, utilizing the precise control of Ta-doping concentration using the atomic layer deposition (ALD) supercycle process. We systematically studied the chemical composition and crystal structure of ALD Ta-doped ZrO2 and its effects on the electrical properties of MIM capacitors. It was shown that ZrO2 becomes more stoichiometric with the introduction of Ta, which is attributed to the suppression of oxygen vacancy (VO) formation. The change in the atomic arrangement due to the substitution of Zr with Ta and the reduction of VO enhances the crystallinity of the cubic phase and causes a decrease in the molar volume of the ZrO2 films. As a result of the change in the crystal structure along with the high dielectric polarizability of Ta, the dielectric constant of ALD Ta-doped ZrO2 increases by up to 80% compared to that of undoped ZrO2 films. Moreover, the reduction of the VO species suppresses the emission of the carriers, which lowers the leakage current density by two orders of magnitude in the Ta-doped ZrO2 films as compared to that in the undoped ZrO2 films. In general, the dielectric constant and leakage currents have a trade-off relationship in a single high-k dielectric system. Consequently, proper doping of Ta into ZrO2 using ALD is a promising solution to overcome the technical limits of conventional high-k dielectrics.

Downscaling of complementary metal-oxide semiconductor (CMOS) gate stacks requires the introduction of ultra-thin and high-k dielectrics such as HfO2. Atomic layer deposition (ALD) is an excellent technique for producing high-quality high-k films. During ALD, chemical reactions on the substrate surface involve multiple processes that affect the chemical and electrical properties of the deposited films. Thus, the choice of an appropriate precursor for ALD is critical for obtaining high-quality high-k films, leading to good device performance. The aim of this study is to understand the surface reactions during the film growth along with the evaluation of the electrical properties of HfO2 deposited using two different Hf precursors, HfCl4 and Hf(N(CH3)2)4. The growth behavior and electrical performance of ALD HfO2 thin films obtained using the two Hf precursors and H2O as an oxidant at 250 °C are studied comparatively and discussed as a function of the process parameters, together with surface-reaction energetics determined by the density functional theory. Compared to Hf(N(CH3)2)4, the HfCl4 shows unfavorable nucleation behavior on the starting Si–OH surfaces. In addition, a more stoichiometric HfO2 film results from HfCl4 owing to its high reactivity, leading to lower leakage currents of Si-based devices than that of the film obtained from Hf(N(CH3)2)4. Further, HfCl4 showed better nucleation on a 2D graphene substrate, leading to superior electrical performance in graphene-based field effect transistors. These results provide practical insights on selecting a suitable Hf precursor for producing gate dielectric layers for future nanoelectronics.

With accelerated shrinking of integrated circuit, the fabrication of metal-insulator-metal (MIM) capacitors having a high capacitance density and low leakage current for dynamic random access memory (DRAM) has become a challenge. In this study, we investigated Y-stabilized ZrO2 as a novel high-k material for DRAM capacitors. We used atomic layer deposition (ALD) to produce Y-stabilized ZrO2; this technique enables easy control of the Y concentration by changing the ratio of ZrO2 to Y2O3 ALD cycles. This technique is suitable for future DRAM capacitors, as it provides superior thickness controllability and conformality. Y doping into ZrO2 increases the oxygen vacancy content in the films and transforms the ZrO2 crystal structure from monoclinic to cubic. As a result, the dielectric constant is significantly increased from 19.1 to 30.2. Moreover, Y doping shifts the defect level into the conduction band rather than the energy bandgap, resulting in about 60 times lower leakage current density for Y-doped ZrO2 compared to undoped ZrO2. It is notable that the dielectric properties and the leakage current density are simultaneously enhanced, indicating that Y-doped ZrO2 is a promising candidate to satisfy the requirements of future DRAM capacitors.

This paper investigates the impact of an atomic layer-deposited Y2O3 dielectric on the passivation of a GeO2 layer in GeO2-based Ge gate stacks. The equivalent oxide thickness scalability and thermal stability of the ultrathin Y2O3 layer are evaluated at different Y2O3 thicknesses and annealing conditions in detail. Experimental results show that a Y2O3 layer thickness of 1.0 nm is required to serve as a GeO2 passivation layer while retaining gate-stack performance at 400 °C postdeposition annealing. However, at a higher annealing temperature of 500 °C, the barrier property deteriorates and allows GeO desorption. The proposed gate-stack implies the applicability of a Y2O3 passivation method for further scaled GeO2-based Ge gate stacks.

Background: Renal function is closely related to cardiac function and an important prognostic marker in heart failure. Objective: We aimed to test the prognostic value of cystatin C (cysC)-derived estimated glomerular filtration rates (eGFR) in comparison with eGFRs from creatinine solely based equations in patients with acute heart failure (AHF). Methods: This study included 262 patients (65.8 ± 14.9 years old, 126 male) with AHF. Prognostic value of the eGFRs, from cysC-based equations chronic kidney disease epidemiology collaboration (CKD-EPI-cysC and CKD-EPI-creatinine [cr]-cysC equations) were compared with eGFRs calculated from serum creatinine levels only (Modification of Diet in Renal Disease [MDRD]-4 and CKD-EPI-cr equations). Prognosis was evaluated with the composite of all-cause mortality and hospitalization for heart failure within 1 year. Results: During the follow-up period (mean follow-up period, 264.0 ± 136.1 days), 67 (25.6%) events occurred. Estimated GFR using CKD-EPI-cysC was the best for predicting 1-year outcome using receiver operating characteristic curve analysis (area under curve 0.585, 0.607, 0.669, and 0.652 for eGFRs from MDRD-4, CKD-EPI-cr, CKD-EPI-cysC, and CKD-EPI-cr-cysC respectively). The Kaplan-Meier survival curve analysis showed that only the eGFRs classification from the equations based on cysC significantly predicted 1-year outcome in patients with AHF. Conclusions: Estimated GFRs calculated with cysC predicted the prognosis more accurately in patients with AHF than the eGFRs from creatinine only equations.

Atomic layer deposition (ALD) of HfO2 is a key technology for the application of high dielectric constant gate dielectrics ranging from conventional Si devices to novel nanodevices. The effects of the precursor on the growth characteristics and film properties of ALD HfO2 were investigated by using hafnium tetrachloride (HfCl4) and bis(ethylcyclopentadienyl)hafnium dichloride (Hf(EtCp)2Cl2, Hf(C2H5C5H4)2Cl2) with O2 plasma reactant. The growth characteristics were significantly affected even by simply changing the precursor. Theoretical calculations utilizing geometrical information on the precursor and density functional theory revealed that the steric demands of the precursor ligands have a dominant effect on the different growth characteristics rather than the reaction probability of the precursor on the surface. The chemical compositional analysis results showed that the Cl residue in the HfO2 films was reduced by using Hf(EtCp)2Cl2 due to the lower number of Cl atoms in each Hf precursor molecule and...

We investigate effects of bottom electrodes on ZrO2 thin films formed through atomic layer deposition (ALD). We focus on the correlation between interfacial layer formation and electrical properties. For this comparative study, two different bottom electrodes consisting of TiN and Ru were employed. ALD ZrO2 films are deposited on these bottom electrodes by using tris(dimethylamino)cyclopentadielnyl zirconium ((C5H5)Zr[N(CH3)2]3) and ozone as a precursor and oxidant, respectively. Based on detailed investigations using transmission electron microscopy and X-ray photoelectron spectroscopy, we are able to comparatively characterize the formations and chemical compositions of the interfacial layers between ALD ZrO2 and both bottom electrodes. Based on the electrical properties of metal-insulator-metal capacitors fabricated using both the TiN and Ru bottom electrodes, we observe improved capacitance-voltage and current-voltage characteristics with the Ru bottom electrode, which are attributed to the suppressed formation of an interfacial layer. We also discuss the correlation between traps in the interfacial layer and electrical properties.

We report a fully transparent thin-film transistor utilizing a La-doped BaSnO3 channel layer that provides a drain current of 0.468 mA/μm and an on-off ratio of 1.5 × 108. The La-doped BaSnO3 channel is grown on a 100–150 nm thick unintentionally doped BaSnO3 buffer layer on a (001) MgO substrate by molecular-beam epitaxy. Unpatterned channel layers show mobilities of 127–184 cm2 V−1 s−1 at carrier concentrations in the low to mid 1019 cm−3 range. The BaSnO3 is patterned by reactive ion etching under conditions preserving the high mobility and conductivity. Using this patterning method, a sub-micron-scale thin film transistor exhibiting complete depletion at room temperature is achieved.

A method for significantly increasing the growth rates (GRs) of high- k oxide thin films grown via plasma-enhanced atomic layer deposition (PE-ALD) by enhancing the plasma density through the addition of Ar gas to the O

With the acceleration of the scaling down of integrated circuits, it has become very challenging to fabricate a metal-insulator-metal (MIM) capacitor with a high capacitance density and low leakage current for nanoscale dynamic random access memory. Yttria-stabilized-zirconia (YSZ) thin films, one of the insulators in the constitution of MIM capacitors, have been reported to have various crystal structures from the monoclinic phase to the cubic phase according to different Y doping levels. The electrical characteristics depend on the crystal structure of the YSZ thin film. Here, we report the local crystallization of YSZ thin films via Joule heating and the leakage current induced during in situ transmission electron microscopy biasing tests. We studied the crystallization process and the increase in the leakage current using experimental and simulation results. It is important to understand the relationship between the crystallinity and electrical properties of YSZ thin films in MIM capacitors.