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The ferroelectricity in fluorite-structure oxides such as hafnia and zirconia has attracted increasing interest since 2011. They have various advantages such as Si-based complementary metal oxide semiconductor-compatibility, matured deposition techniques, a low dielectric constant and the resulting decreased depolarization field, and stronger resistance to hydrogen annealing. However, the wake-up effect, imprint, and insufficient endurance are remaining reliability issues. Therefore, this paper reviews two major aspects: the advantages of fluorite-structure ferroelectrics for memory applications are reviewed from a material's point of view, and the critical issues of wake-up effect and insufficient endurance are examined, and potential solutions are subsequently discussed.
Using data from the Research on Asian Psychotropic Prescription Patterns for Antidepressants (REAP-AD) study, we aimed to present the rates and clinical correlates of suicidal thoughts/acts in patients recruited from a total of 40 centres in 10 Asian countries/areas: China, Hong Kong, India, Indonesia, Japan, Korea, Malaysia, Singapore, Taiwan, and Thailand.
Data from 1122 patients with depressive disorders in the REAP-AD study were used. The ICD-10 was employed to diagnose depressive episodes and recurrent depressive disorder. The presence or absence of suicidal thoughts/acts and profile of other depressive symptoms was established using the National Institute for Health and Clinical Excellence guidelines for depression. Country/area differences in rates of suicidal thoughts/acts were evaluated with the χ2 test. In addition, depressive symptom profiles, other clinical characteristics, and patterns of psychotropic drug prescription in depressed patients with and without suicidal thoughts/acts were compared using analysis of covariance for continuous variables and logistic regression analysis for discrete variables to adjust the effects of covariates.
The rates of suicidal thoughts/acts in 10 countries/areas varied from 12.8% in Japan to 36.3% in China. Patients with suicidal thoughts/acts presented more persistent sadness (adjusted odds ratio [aOR]=2.64, p<0.001), loss of interest (aOR=2.33, p<0.001), fatigue (aOR=1.58, p<0.001), insomnia (aOR=1.74, p<0.001), poor concentration (aOR=1.88, p<0.001), low self-confidence (aOR=1.78, p<0.001), poor appetite (aOR=2.27, p<0.001), guilt/self-blame (aOR=3.03, p<0.001), and use of mood stabilisers (aOR=1.79, p<0.001) than those without suicidal thoughts/acts.
Suicidal thoughts/acts can indicate greater severity of depression, and are associated with a poorer response to antidepressants and increased burden of illness. Hence, suicidal thoughts/acts can provide a clinical index reflecting the clinical status of depressive disorders in Asians.
The formation and morphological evolution of germanides formed in a ternary Ni/Ta-interlayer/Ge system were examined by ex situ and in situ annealing experiments. The Ni germanide film formed in the Ni/Ta-interlayer/Ge system maintained continuity up to 550°C, whereas agglomeration of the Ni germanide occurred in the Ni/Ge system without Ta-interlayer. Through microstructural and chemical analysis of the Ni/Ta-interlayer/Ge system during and after in situ annealing in a transmission electron microscope, it was confirmed that the Ta atoms remained uniformly on the top of the newly formed Ni germanide layer during the diffusion reaction. Consequently, the agglomeration of the Ni germanide film was retarded and the thermal stability was improved by the Ta incorporation.
The oxidation mechanism and thermal stability of nickel oxide (NiO)/carbon nanotube (CNT) composites were investigated by examining composites with different NiO contents by thermogravimetric analysis and transmission electron microscopy (TEM). NiO acts as a catalyst in the oxidation of CNT in the composite. CNTs can be oxidized, even in a vacuum, by reducing NiO to nickel at temperatures lower than the normal oxidation temperature of CNTs. This phase transition was confirmed directly by in situ heating TEM observations. In air, reduction by CNT occurs simultaneously with reoxidation by gaseous O2 molecules, and NiO maintains its phase. The thermal stability decreased with increasing NiO content because of defects in the CNT generated by the NiO loading.
Analytical electron microscopy (AEM) was used to examine the initial interfacial reaction layers between a eutectic Sn–3.5Ag solder and an electroless nickel-immersion gold-plated (ENIG) Cu substrate during reflow at 255 °C for 1 s. AEM confirmed that a thick upper (Au,Ni)Sn2 layer and a thin Ni3Sn4 layer had formed through the reaction between the solder and ENIG. The amorphous electroless Ni(P) plated layer transformed into two P-rich Ni layers. One is a crystallized P-rich Ni layer, and the other is an intermediate state P-rich Ni layer before the crystallization. The crystallized P-rich layer consisted of Ni2P and Ni12P5. A thin Ni2P layer had formed underneath the Ni3Sn4 layer and is believed to be a predecessor of the Ni2SnP ternary phase. A Ni12P5 phase was observed beneath the Ni2P thin layer. In addition, nanocrystalline Ni was found to coexist with the amorphous Ni(P) phase in the intermediate state P-rich Ni layer.
Raman scattering and optical absorption spectroscopy are used for the chirality characterization of HiPco single wall carbon nanotubes (SWNTs) dispersed in aqueous solution with the surfactant sodium dodecylbenzene sulfonate. Radial breathing mode (RBM) Raman peaks for semiconducting and metallic SWNTs are identified by directly comparing the Raman spectra with the Kataura plot. The SWNT diameters are calculated from these resonant peak positions. Next, a list of (n, m) pairs, yielding the SWNT diameters within a few percent of that obtained from each resonant peak position, is established. The interband transition energies for the list of SWNT (n, m) pairs are calculated based on the tight binding energy expression for each list of the (n, m) pairs, and the pairs yielding the closest values to the corresponding experimental optical absorption peaks are selected. The results reveal (1, 11), (4, 11), (5, 12), and (5, 9) among the most probable chiralities for the semiconducting nanotubes. The results also reveal that (4, 16), (6, 12) and (8, 8) are the most probable chiralities for the metallic nanotubes. Directly relating the Raman scattering data to the optical absorption spectra, the present method is considered the simplest technique currently available. Another advantage of this technique is the use of the, E11S, E33S, and E22M peaks in the optical absorption spectrum in the analysis to enhance the accuracy in the results.
To evaluate risk factors and treatment outcomes of bloodstream infections caused by extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP).
Retrospective case-control study. Stored blood isolates of K. pneumoniae were tested for ESBL production by NCCLS guidelines, double-disk synergy test, or both.
A 1,500-bed, tertiary-care university hospital and referral center.
Sixty case-patients with bacteremia due to ESBL-KP were compared with 60 matched control-patients with non-ESBL-KP.
There were no significant differences in age, gender, APACHE II score, or underlying diseases between the groups. Independent risk factors for infections caused by ESBL-KP were urinary catheterization, invasive procedure within the previous 72 hours, and an increasing number of antibiotics administered within the previous 30 days. Complete response rate, evaluated 72 hours after initial antimicrobial therapy, was higher among control-patients (13.3% vs 36.7%; P = .003). Treatment failure rate was higher among case-patients (35.0% vs 15%; P = .011). Overall 30-day mortality rate was 30% for case-patients and 28.3% for control-patients (P = .841). Case-patients who received imipenem or ciprofloxacin as a definitive antibiotic had 10.5% mortality. The mortality rate for initially ineffective therapy was no higher than that for initially effective therapy (9.1% vs 11.1%; P = 1.000), but statistical power was low for evaluating mortality in the absence of septic shock.
For K. pneumoniae bacteremia, patients with ESBL-KP had a higher initial treatment failure rate but did not have higher mortality if antimicrobial therapy was appropriately adjusted in this study with limited statistical power.
In this work, transparent flexible substrates based on polyimides(PI) with indium tin oxide (ITO) thin films for organic electroluminescent devices have been prepared. 2,2'-bis-(3,4- dicarboxyphenyl) hexafluoropropanedianhydride (6FDA) and 2,2'-bis-(trifluoromethyl)-4,4'- diaminobiphenyl (TFDB) PI films were used for transparent flexible substrates. ITO thin films were prepared at two substrate deposition temperatures of 25°C and 150°C with a typical radio- frequency (r.f.) planar magnetron sputtering system. The sheet resistance and the optical transmission properties of the fluorinated PI substrate were comparable with those for the slide glass substrate. The substrate properties are better when the deposition temperature is higher. SiO2 coating onto the fluorinated PI substrate by sol-gel reaction was also attempted to improve the optical transmission of the ITO/PI substrate. It was found that the coating of SiO2 affected on the morphology of the PI substrates.
AlxGa1-xN sample with x=0.36 was epitaxially grown on sapphire by MOCVD. SAW velocity of 5420 m/s and TCF (temperature coefficient of frequency) of -51.20 ppm/°C were measured from the SAW devices fabricated on the AlxGa1-xN sample, when kh value was 0.078, at temperatures between –30 °C and 60 °C Electromechanical coupling coefficient was ranged from 1.26 % to 2.22 %. The fabricated SAW filter have shown a good device performance with insertion loss of -33.853 dB and side lobe attenuation of 20 dB.
We report a new poly-Si TFT, of which the troublesome implantation damage near the source/drain junction was eliminated, by performing source/drain ion implantation as well as excimer laser annealing (ELA) prior to the gate formation. The recrystallization of a-Si in the channel region and the dopant activation in the source/drain region were simultaneously accomplished by single ELA process step so that the implantation damage, which results in large leakage current of TFT, has been successfully eliminated. TEM image verifies that large poly-Si grains were successfully grown from the ion implanted source/drain region to the channel region. The proposed poly-Si TFT, of which mobility is 171 cm2/Vs, exhibits a large on/off current ratio exceeding 4.1 × 107 without LDD or offset structure while those of the conventional TFT, which has been fabricated simultaneously for the comparison purpose, are 86 cm2/Vs and 6.1 × 106.
A new self-aligned poly-Si TFT has been fabricated by employing a photoresist backside exposure technique. A pre-patterned aluminum (Al) layer on a-Si film not only induces the lateral grain growth (∼1.6 μm) in excimer laser crystallization but also implements the selfalignment of the gate region with the lateral grain region. Photoresist backside exposure through poly-Si film has been successfully performed because crystallized poly-Si has a fairly high UV transmittance. A self-aligned poly-Si TFT with a single grain boundary within the 2 μm channel was successfully fabricated and high on/off current ratio (∼107) was obtained.
A new excimer laser annealing method is proposed in order to produce the poly-Si film with low defect density and large grain, by combining the selective Si ionimplantation and excimer laser annealing. Selective Si ion-implantation is employed to form artificial nucleation seeds in a-Si film prior to excimer laser annealing in order to increase the nucleation probability. The grain boundary location in poly-Si film has been controlled through implantation mask, and the grain size around micrometer order is obtained without any other process. TEM result shows that grain boundary is controlled according to mask pattern and the crystallinity of the poly-Si film is improved.
We have proposed and fabricated a new poly-Si TFT that employs selectively doped regions between the source and drain in order to reduce leakage current without the sacrifice of the on current. In the proposed poly-Si TFTs, the selectively doped regions where doping concentration is identical to that of source/drain, reduce the effective channel length during the on state. Under the off state, the selectively doped regions may reduce the lateral electric field induced in the depletion region near drain so that the leakage current reduces considerably. The experimental data of the proposed TFT shows that it has the high on-current, low leakage current and low threshold voltage when compared with conventional TFT. The fabrication steps for the proposed TFT are reduced because ion-implantation for source/drain and selectively doped regions is performed simultaneously prior to an excimer laser irradiation. It should be noted that, in the proposed TFT, only one excimer laser annealing is required while two excimer laser annealing steps are required in conventional TFT.
We propose new poly-Si TFT's with selectively doped region in the center of channel in order to reduce large leakage current. In proposed TFT's, the selectively doped region redistributes total induced electric field in the channel. For VGS<0, VDS> 0 in the n-channel proposed TFT's, most of the high electric field applies in the depletion regions which exist the drain/undoped region and undoped region/selectively doped region which faces to the source. Comparing with conventional TFT's, the electric field induced near the drain junction reduces to about 1/2, therefore, electron-hole pairs generated in drain junction are considerably reduced. Furthermore, the ON-current of proposed TFT's is the same or slightly lower than that of conventional ones. Consequently, the experimental data show the considerable improvement of the ON/OFF current ratio.
A novel method to control the recrystallization depth of amorphous silicon (a-Si) film during the excimer laser annealing (ELA) is proposed in order to preserve a-Si that is useful for fabrication of poly-Si TFT with a-Si offset in the channel. A XeCl excimer laser beam is irradiated on a triple film structure of a-Si thin native silicon oxide (~20Å)/thick a-Si layer. Only the upper a-Si film is recrystallized by the laser beam irradiation, whereas the lower thick a-Si film remains amorphous because the thin native silicon oxide layer stops the grain growth of the poly-crystalline silicon (poly-Si). So that the thin oxide film sharply divides the upper poly-Si from the lower a-Si.
Excimer laser annealing method employing artificial nucleation seed is proposed to increase the grain size of polycrystalline silicon(poly-Si). We utilize Si component incorporated in aluminum(Al)-sputtering source for the nucleation seed. Si clusters which are to be used as nucleation seed are successfully formed on the substrate by deposition and etch-back of Si-incorporated Al layer. Irradiation of excimer laser on amorphous silicon(a-Si) film deposited on the substrate prepared by our method results in enlargement of poly-Si grains, compared with conventional laser recrystallization. Poly-Si thin film transistor also shows much improved electrical perfbrmance which directly reflects the quality of poly-Si film recrystallized by our method.
Lateral FEAs which have three terminals, stable anode current, and suppressed gate current are proposed and fabricated. In order to eliminate the path of electrons between tips and anode, the proposed FEAs are sealed by evaporation of oxide while Molybdenium in our privious work. Experimental results such as controllibility of gate electrode, a portion of the gate current for the anode current, and stability of the anode current are given. The proposed FEAs exhibit an excellent controllibility by gate electrode and stability of the emission current. The gate current of new FEAs is negligible compared with the ande current while that of the privious FEAs is about 20% of the anode current.
We fabricated a new device, which employs counter-doped lateral body terminal (CLBT) in order to suppress kink effects and improve the device stability. Proposed device also employs a buried channel (BC), which increases ON-current and operating frequency. Although LDD structure is not employed in the proposed device, low OFF-current is successfully obtained due to elimination of minority carrier through CLBT. We have measured the dynamic properties of poly-Si TFT device and circuit. The reliability of TFT and circuits after AC stress is also discussed in our paper.
The proposed poly-Si TFT has high ON-current and low OFF-current compared with conventional 3-terminal poly-Si TFT. The 4-terminal device characteristics were measured with source and CLBT shorted. The proposed device exhibits superior performance to conventional device in ON-current because BC prevents carrier scattering to gate oxide. We have performed bias and high temperature stress test of ring oscillator in order to investigate dynamic reliability between conventional poly-Si TFT and proposed 4-terminal poly-Si TFT. Our experimental results show that BC enables the device to have high mobility and switching frequency (33MHz at VDD=15V). The minority carrier elimination of CLBT suppresses kink effects and makes superb dynamic reliability of CMOS circuit.
We have fabricated a new three-terminal lateral field emitter structure in which the anode current is limited by the channel current of undoped region. The new device exhibits an excellent stability of the emission current. The field emission characteristics of fabricated device have two modes. In the first mode below 89 V, the mechanism of emission is identical to that of conventional poly-Si emitters and, in the second mode above 89 V, the emission current is limited by the inversion charges in the channel, so stable anode current is maintained. Furthermore, the fabrication process of the device is very simple.