Abstract
We report the basic electrical characteristics and uniformity of 25 Au/Ni Schottky barrier diodes (SBDs) with three different surface treatments ((I) no treatment (as-grown), (II) alkaline ...solution, and (III) HCl related solution) before and after post-metallization annealing at 400 °C. The SBDs with (II) showed small diode-to-diode variation in the Schottky barrier height and the ideality factor, and good uniformity over the electrode. In addition, after the annealing, the reverse-biased current significantly reduced to the prediction by the thermionic field emission model. Similar characteristics were obtained for the SBDs with (I), however, the uniformity over the electrode became worse after the annealing. For the SBDs with (III), the diode-to-diode variation was originally large, and the reverse-biased current did not significantly reduce. In addition, inhomogeneity with a line-shape pattern was observed in some SBDs with the large reverse-biased current. Residual Cl atoms may be responsible for low-barrier nature.
For accelerating the development of GaN power-switching devices, current knowledge on the origins and dynamic properties of the major intrinsic nonradiative recombination centers (NRCs) in Mg-doped ...GaN (GaN:Mg) are reviewed, as lightly to heavily doped p-type planar GaN segments are required but certain compensating defects including NRCs hinder their formation. The results of complementary time-resolved photoluminescence and positron annihilation spectroscopy measurements on the epitaxial and ion-implanted GaN:Mg formed on low dislocation density GaN substrates indicate the following: major intrinsic NRCs are the clusters of Ga vacancies (VGas) and N vacancies (VNs), namely VGa(VN)2 in the epitaxial GaN:Mg and (VGa)3(VN)3 in the ion-implanted GaN:Mg after appropriate thermal annealings. The minimum electron capture-cross-sections of VGa(VN)2 and (VGa)3(VN)3 are commonly the middle of 10−13 cm2 at 300 K, which is approximately four times larger than the hole capture-cross-section of the major intrinsic NRCs in n-type GaN, namely VGaVN divacancies, being 7 × 10−14 cm2.
Vacancy‐type defects in Mg‐implanted GaN were probed using a monoenergetic positron beam. Mg ions of multiple energies (15–180 keV) were implanted to provide a 200‐nm‐deep box profile with Mg ...concentration of 4 × 1019 cm−3. The major defect species of vacancies introduced by Mg‐implantation was a complex between Ga‐vacancy (VGa) and nitrogen vacancies (VNs). After annealing above 1000 °C, these defects started to agglomerate, and the major defect species became (VGa)2 coupled with VNs. The defect reaction occurred between not only the defects introduced by the implantation but also the defects introduced by an excess Mg‐doping. The depth distribution of vacancy‐type defects agreed well with that of implanted Mg, and no large change in the distribution was observed up to 1300°C annealing. Relationships between photoluminescence bands and vacancy‐type defects introduced by Mg‐implantation are also discussed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Objective
To determine T2* normal reference values for anterior talofibular ligament (ATFL) and to investigate the feasibility of the quantitative ATFL quality evaluation in chronic lateral ankle ...instability (CLAI) using T2* values.
Materials and methods
This study enrolled 15 patients with CLAI and 30 healthy volunteers. The entire ATFL T2* values from the MRI T2* mapping were measured. The prediction equation (variables: age, height, and weight) in a multiple linear regression model was used to calculate the T2* normal reference value in the healthy group. T2* ratio was defined as the ratio of the actual T2* value of the patient’s ATFL to the normal reference value for each patient. A Telos device was used to measure the talar tilt angle (TTA) from the stress radiograph.
Results
T2* values of ATFL in the healthy and CLAI groups were 10.82 ± 1.84 ms and 14.36 ± 4.30 ms, respectively, which are significantly higher in the CLAI group (
P
< 0.05). The prediction equation of the normal reference T2* value was 14.9 + 0.14 × age (years) − 4.7 × height (m) − 0.03 × weight (kg) (
R
2
= 0.65,
P
< 0.0001). A significant positive correlation was found between the T2* ratio and TTA (
r
= 0.66,
P
= 0.007).
Conclusion
MRI T2* values in patients with CLAI were higher than those in healthy participants, and the T2* ratio correlated with TTA, suggesting that T2* values are promising for quantitative assessment of ATFL quality preoperatively.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Inefficient Mg-induced p-type doping has been remained a major obstacle in the development of GaN-based electronic devices for solid-state lighting and power applications. This study reports ...comparative structural analysis of defects in GaN layers on freestanding GaN substrates where Mg incorporation is carried out via two approaches: ion implantation and epitaxial doping. Scanning transmission electron microscopy revealed the existence of pyramidal and line defects only in Mg-implanted sample whereas Mg-doped sample did not show presence of these defects which suggests that nature of defects depends upon incorporation method. From secondary ion mass spectrometry, a direct correspondence is observed between Mg concentrations and location and type of these defects. Our investigations suggest that these pyramidal and line defects are Mg-rich species and their formation may lead to reduced free hole densities which is still a major concern for p-GaN-based material and devices. As freestanding GaN substrates offer a platform for realization of p-n junction-based vertical devices, comparative structural investigation of defects originated due to different Mg incorporation processes in GaN layers on such substrates is likely to give more insight towards understanding Mg self-compensation mechanisms and then optimizing Mg doping and/or implantation process for the advancement of GaN-based device technology.
The Rho/Rho-kinase pathway plays an important role in many cardiovascular diseases such as hypertension, atherosclerosis, heart failure, and myocardial infarction. Although previous studies have ...shown that Rho-kinase inhibitors reduce ischemia/reperfusion (I/R) injury and cytokine production, the role of Rho-kinase in leukocytes during I/R injury is not well understood. Mice were subjected to 30-min ischemia and reperfusion. Rho-kinase activity was significantly greater in leukocytes subjected to myocardial I/R compared to the sham-operated mice. Administration of fasudil, a Rho-kinase inhibitor, significantly reduced the I/R-induced expression of the proinflammatory cytokines interleukin (IL)-6, C-C motif chemoattractant ligand 2 (CCL2), and tumor necrosis factor (TNF)-α, in leukocytes, compared with saline as the vehicle. Furthermore, fasudil decreased I/R-induced myocardial infarction/area at risk (IA) and I/R-induced leukocyte infiltration in the myocardium. Interestingly, IA in fasudil-administered mice with leukocyte depletion was similar to that in fasudil-administered mice. I/R also resulted in remarkable increases in the mRNA expression levels of the proinflammatory cytokines TNF-α, IL-6, and CCL2 in the heart. Inhibition of Rho-kinase activation in leukocytes has an important role in fasudil-induced cardioprotective effects. Hence, inhibition of Rho-kinase may be an additional therapeutic intervention for the treatment of acute coronary syndrome.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Threshold voltage instability (shift) due to positive bias stress in GaN planar-gate MOSFETs was investigated. Gate dielectric (SiO
2
) was formed by remote-plasma-assisted CVD on homoepitaxial ...Mg-doped p-type GaN layers with Si-implanted n-type source and drain regions. The threshold voltage shift of 5.8 V was observed after a stress voltage of 30 V for a sample without post-deposition annealing (PDA). The threshold voltage shift was significantly reduced to 1.4 V for a sample with PDA (800 °C for 30 min). Stress time dependences up to 6000 s were measured, revealing that the main origin of the threshold voltage shift is electron trapping into near interface traps (NITs). These results suggest that PDA is effective for the reduction of the NITs.
Background and aim
Long-term cumulative incidence of and risk factors for metachronous advanced colorectal neoplasia, including both advanced colorectal adenoma (≥10 mm, or with villous or high-grade ...dysplasia) and colorectal cancer, are critical for surveillance strategies. The aim of this study was to determine the cumulative incidence of metachronous advanced colorectal neoplasia and its risk factors.
Methods
A retrospective cohort study was conducted on 6720 consecutive individuals who underwent general health check-ups and colonoscopy. Colorectal adenomas at initial colonoscopy were categorized as low-risk (1–2 small <10 mm tubular adenomas) or high-risk adenoma (≥3 tubular adenomas of any size; at least one adenoma ≥10 mm; or villous adenoma or adenoma with high-grade dysplasia). Kaplan–Meier estimates and hazard ratio by Cox-proportional hazard regression were calculated.
Results
The cumulative incidence (95% confidence interval CI) of metachronous advanced colorectal neoplasia at 5 and 10 years was 5.7% 4.6–7.1, and 11% 8.9–14 in the low-risk adenoma group, and 10% 8.6–13, and 17% 14–21 in high-risk adenoma group, respectively. Adjusted hazard ratio 95% CI of low-risk adenoma (vs. no colorectal adenoma), high-risk adenoma (vs. no colorectal adenoma), current smoking and positive fecal immunochemical test were 1.34 1.04–1.74, 1.94 1.48–2.55, 1.55 1.2–2.02 and 1.69 1.35–2.1, respectively. Adjusted hazard ratio 95% CI of positive fecal immunochemical test was 1.88 1.29–2.74 in those with normal colonoscopy.
Conclusions
Both low-risk and high-risk adenomas confer substantial risk for metachronous advanced colorectal neoplasia at 10 years. Positive fecal immunochemical test was a significant risk factor for metachronous advanced colorectal neoplasia despite normal colonoscopy.
Mg-doped p-type gallium nitride (GaN) layers with doping concentrations in the range from 6.5 × 1016 cm−3 (lightly doped) to 3.8 × 1019 cm−3 (heavily doped) were investigated by Hall-effect ...measurement for the analysis of hole concentration and mobility. p-GaN was homoepitaxially grown on a GaN free-standing substrate by metalorganic vapor-phase epitaxy. The threading dislocation density of p-GaN was 4 × 106 cm−2 measured by cathodoluminescence mapping. Hall-effect measurements of p-GaN were carried out at a temperature in the range from 130 to 450 K. For the lightly doped p-GaN, the acceptor concentration of 7.0 × 1016 cm−3 and the donor concentration of 3.2 × 1016 cm−3 were obtained, where the compensation ratio was 46%. We also obtained the depth of the Mg acceptor level to be 220 meV. The hole mobilities of 86, 31, 14 cm2 V−1 s−1 at 200, 300, 400 K, respectively, were observed in the lightly doped p-GaN.
The photoluminescences of ion-implanted (I/I) and epitaxial Mg-doped GaN (GaN:Mg) are compared. The intensities and lifetimes of the near-band-edge and ultraviolet luminescences associated with a ...MgGa acceptor of I/I GaN:Mg were significantly lower and shorter than those of the epilayers, respectively. Simultaneously, the green luminescence (GL) became dominant. These emissions were quenched far below room temperature. The results indicate the generation of point defects common to GL and nonradiative recombination centers (NRCs) by I/I. Taking the results of positron annihilation measurement into account, N vacancies are the prime candidate to emit GL and create NRCs with Ga vacancies, (VGa)m(VN)n, as well as to inhibit p-type conductivity.
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