We report the effect of YO passivation by atomic layer deposition (ALD) using various oxidants, such as HO, O plasma, and O, on In-Ga-Zn-O thin-film transistors (IGZO TFTs). A large negative shift in the threshold voltage (V) was observed in the case of the TFT subjected to the HO-ALD YO process; this shift was caused by a donor effect of negatively charged chemisorbed HO molecules. In addition, degradation of the IGZO TFT device performance after the O plasma-ALD YO process (field-effect mobility (μ) = 8.7 cm/(V·s), subthreshold swing (SS) = 0.77 V/dec, and V = 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 O-ALD YO process led to enhanced device stability under light illumination (ΔV = -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 thickness under the current investigation) showed more stable device performance than TFTs with a thinner IGZO film (30 nm) (ΔV = -0.4 V after 3 h of light illumination) by triggering the recombination of holes diffusing from the IGZO surface to the insulator-channel interface. Therefore, we envisioned that the O-ALD YO passivation layer suggested in this paper can improve the photostability of TFTs under light illumination.

Theoretical and experimental studies were performed on surface reactions during film growth and electrical properties of HfO2 using two different Hf precursors, HfCl4 and Hf(N(CH3)2)4.

Atomic layer deposition (ALD) of HfO 2 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 HfO 2 were investigated by using hafnium tetrachloride (HfCl 4 ) and bis(ethylcyclopentadienyl)hafnium dichloride (Hf(EtCp) 2 Cl 2, Hf(C 2 H 5 C 5 H 4 ) 2 Cl 2 ) with O 2 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 HfO 2 films was reduced by using Hf(EtCp) 2 Cl 2 due to the lower number of Cl atoms in each Hf precursor molecule and the relieved bridge formation of Hf−Cl−Hf bridge on the surface compared to HfCl 4 . The electrical property measurement results showed significantly improved insulating properties in HfO 2 using Hf(EtCp) 2 Cl 2 compared to HfCl 4 due to the low concentration of Cl residue in the film. These results provide broad insights to researchers who are interested in the fabrication of high quality dielectric layers to achieve better device performance and overcome physical limitations in the nanoscale regime.

No abstract

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.