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We report on the formation of shallow junctions with high activation in both n+/p and p+/n Ge junctions using ion implantation and Flash Lamp Annealing (FLA). The shallowest junction depths (Xj) formed for the n+/p and p+/n junctions were 7.6 nm and 6.1 nm with sheet resistances (Rs) of 860 ohms/sq. and 704 ohms/sq., respectively. By reducing knocked-on oxygen during ion implantation in the n+/p junctions, Rs was decreased by between 5% and 15%. The lowest Rs observed was 235 ohms/sq. with a junction depth of 21.5 nm. Hall measurements clearly revealed that knocked-on oxygen degraded phosphorus activation (carrier concentration). In the p+/n Ge junctions, we show that ion implantation damage induced high boron activation. Using this technique, Rs can be reduced from 475 ohms/sq. to 349 ohms/sq. These results indicate that the potential for forming ultra-shallow n+/p and p+/n junctions in the nanometer range in Ge devices using FLA is very high, leading to realistic monolithically-integrated Ge CMOS devices that can take us beyond Si technology.
The risk of malaria outbreak surfaced in Vanuatu after Tropical Cyclone (TC) Pam in March 2015. In June and July 2015 we conducted malariometric surveys on the islands of Tanna, Aneityum, and Erromango in Tafea Province, where malaria elimination had been targeted, to determine if malaria incidence had increased after TC Pam. No Plasmodium infection was detected by microscopy and PCR in 3009 survey participants. Only 6·3% (190/3007) of participants had fever. Spleen rates in children aged ⩽12 years from Aneityum and Tanna were low, at 3·6% (14/387) and 5·3% (27/510), respectively. Overall bed net use was high at 72·8% (2175/2986); however, a significantly higher (P < 0·001) proportion of participants from Aneityum (85·9%, 796/927) reported net use than those from Tanna (67·1%, 751/1119) and Erromango (66·8%, 628/940). A recent decrease in malaria incidence in Tafea Province through comprehensive intervention measures had reduced the indigenous parasite reservoir and limited the latter's potential to spur an outbreak after TC Pam. The path towards malaria elimination in Tafea Province was not adversely affected by TC Pam.
A fully coherent free electron laser (FEL) seeded with a higher-order harmonic (HH) pulse from high-order harmonic generation (HHG) is successfully operated for a sufficiently prolonged time in pilot user experiments by using a timing drift feedback. For HHG-seeded FELs, the seeding laser pulses have to be synchronized with electron bunches. Despite seeded FELs being non-chaotic light sources in principle, external laser-seeded FELs are often unstable in practice because of a timing jitter and a drift between the seeding laser pulses and the accelerated electron bunches. Accordingly, we constructed a relative arrival-timing monitor based on non-invasive electro-optic sampling (EOS). The EOS monitor made uninterrupted shot-to-shot monitoring possible even during the seeded FEL operation. The EOS system was then used for arrival-timing feedback with an adjustability of 100 fs for continual operation of the HHG-seeded FEL. Using the EOS-based beam drift controlling system, the HHG-seeded FEL was operated over half a day with an effective hit rate of 20%–30%. The output pulse energy was
at the 61.2 nm wavelength. Towards seeded FELs in the water window region, we investigated our upgrade plan to seed high-power FELs with HH photon energy of 30–100 eV and lase at shorter wavelengths of up to 2 nm through high-gain harmonic generation (HGHG) at the energy-upgraded SPring-8 Compact SASE Source (SCSS) accelerator. We studied a benefit as well as the feasibility of the next HHG-seeded FEL machine with single-stage HGHG with tunability of a lasing wavelength.
To evaluate the effectiveness of a brief suicide management training programme for Japanese medical residents compared with the usual lecture on suicidality.
In this multi-center, clustered randomized controlled trial, the intervention group attended a structured suicide management programme and the control group, the usual lecture on depression and suicidality. The primary outcome was the difference in residents' cumulative competency score to manage suicidal persons from baseline (T0) to 1 month after the intervention (T2), determined using the Suicide Intervention Response Inventory (SIRI-1) score, at individual level.
Analysis of 114 residents (intervention group n = 65, control group n = 49) assigned to two clusters in each group revealed no change in SIRI-1 score from T0 to T2 or immediately after the intervention (T1) between the two groups. As a secondary analysis, discrepancy in judgement between the participants and Japanese suicidologists was examined immediately after the intervention in the adjusted model, with a mean difference in score of 9.98 (95% confidence interval: 4.39–15.56; p = 0.001).
The structured programme was not proven to improve competency in suicide management when measured by the SIRI-1 score. Further elaboration of the programme and valid measurement of its outcome would be needed to show the program's effectiveness.
We have succeeded in pulsed laser annealing of N+ ion-implanted n-type 6H-SiC for increasing the carrier density near surface in order to decrease contact resistance, which induces little redistribution of implanted impurities after laser irradiation. By repeated laser irradiation at low energy density, the ion–implanted impurities were electrically activated without melting the surface region. SiC substrates with impurity concentration of 2×1018 /cm3 were implanted with 30 keV N+ ions with dose of 4.7×1013/cm2. After pulsed laser annealing, a contact resistance was measured to be 5.7×10−5 Ωcm2 using Al electrode on the N+ -implanted layer.
Chlorine radicals generated with UV irradiation are effectively used to remove residual metal contaminants after vatious LSI processes. Aluminum, iron, and copper atoms are effectively removed as volatile chloride species from silicon surfaces. The mechanism has been studied using silicon wafers intentionally contaminated with those metal ions. Contaminants are involved in native oxides as metal oxides or hydroxides. Chlorine radicals penetrate the native oxides and attack those oxides or hydroxides vaporizing metal chlorides. The cleaning process is accompanied with slight etching of silicon surfaces to a depth as thin as a few nm. However, this is not essential because the substrate temperature is more important than the etching depth. Alkaline metals are also removed from the surfaces to the level as small as the detection limit of atomic absorption spectroscopy. We believe that those are removed through a lift-off process. The, wixture of fluorine and hydrogen gases removes a native oxide of silicon under UV irradiation. Hydrogen fluoride radicals react with native oxide resulting in hydrogen termination on silicon dangling bonds. These cleaning processes are advantageous for low temperature silicon epitaxy, reliable contact formation, and thin gate oxide growth.
We review our capacitor technology using (Ba,Sr)TiO3 (BST) as a capacitor dielectric for dynamic random access memory (DRAM) application. Among a number of issues for BST capacitor process integration in DRAM cells, two important technologies are discussed. As an electrode technology, we propose All PErovskite Capacitor (APEC) technology, in which conducting perovskite oxide of SrRuO3 (SRO) is used as capacitor electrodes. For chemical vapor deposition (CVD) of BST, we propose In-situ Multi-Step (IMS) process, which is a sequential repetition of low temperature deposition of ultra thin BST film and crystallization in the same chamber. By using APEC technology and IMS CVD process of BST, we can simultaneously achieve good electrical characteristics (low leakage current and high permittivity) and good step coverage. The combination of APEC technology and IMS CVD process of BST is a promising BST capacitor process technology for future DRAMs.
We have developed a new interconnect technique using a low-k (εt,=2.5) organic interlayer (fluorinated amorphous carbon: a-C:F) and a low-resistivity metal line (copper). The new technique attains a duction in both the capacitance of the interlayer and the resistance of the metal line. We found that a-C:F on Cu reduces reflection to 10% for Kr-F line lithography. However, a-C:F cannot act as a protection layer for oxidation even at 200°C in atmospheric ambient annealing. Cu diffusion into a-C:F is about 100 nm at the annealing temperature of 450°C. The resistivity of the Cu line is 2.3–2.4 μΩ · cm for the 0.5-μm line width. Although the leakage current of the a-C:F ILD is one order higher than that of the SiO2 ILD, electrical isolation is acceptable at < 20 V when annealing is carried out at 350°C in a vacuum.
Wiring capacitance in a multilevel interconnecting structure for sub-quarter-micron ULSI devices has been studied using a simulator called SENECA1), which is developed by the Technical University of Vienna and Sony corporation, for optimizing the structure with low dielectric constant materials as interlevel dielectric layers. The simulation results suggest that an optimized structure model should have an ILD(Inter-Level Dielectrics) thickness of 0.7μm and a metal thickness of 0.4μm for sub-quarter-micron ULSI devices. The application of the low dielectric constant materials to the ULSI devices is examined and also discussed with focusing on feasibility and reliability issues. Calculated wiring capacitance is compared with actual capacitance based on the optimized structure. The 33.2% reduction of capacitance is obtained with using an organic film with dielectric constant of 2.4 in excellent accordance with the simulation.
We investigated developmental changes during the transition from one-word to two-word production, focusing on strategies to lengthen utterances phonologically and to control utterances suprasegmentally. We hypothesized that there is a period of reorganization at the onset of word combinations indicated by decreases in both filler syllables (Fillers) and final syllable lengthening (FSL). The data are from a visually impaired child (Seth) between 1 ; 6.21 and 1 ; 10.26. Seth produced many Fillers until 1 ; 9 when their number decreased for about two weeks after which they changed in nature. FSL was observed until 1 ; 8, but diminished at 1 ; 9. These two regressions coincide with the onset of word combination.
An investigation is made of the role of hollow atoms in the spectra of an ultrashort-pulse-laser-driven Ar cluster target. Experimental measurements are presented from an Ar cluster-gas target using short-pulse lasers with various intensities, durations, and contrasts. Calculations in support of these measurements have been performed using a detailed atomic kinetics model with the ion distributions found from solution of the time-dependent rate equations. The calculations are in good agreement with the measurements and the role of hollow atoms in the resulting complicated spectra is analyzed. It is demonstrated that, although the presence of hollow atoms is estimated to add only around 2% to the total line emission, signatures of hollow atom spectra can be identified in the calculations, which are qualitatively supported by the experimental measurements.
High-resolution K-shell spectra of a plasma created by
superintense laser irradiation of micron-sized Ar clusters have been
measured with an intensity above 1019 W/cm2
and a pulse duration of 30 fs. The total photon flux of 2 ×
108 photons/pulse was achieved for Heα1
resonant line of Ar (λ = 3.9491 Å, 3.14 keV). In parallel
with X-ray measurements, energy distributions of emitted ions have been
measured. The multiply charged ions with kinetic energies up to 800 keV
were observed. It is found that hot electrons produced by high contrast
laser pulses allow the isochoric heating of clusters and shift the ion
balance toward the higher charge states, which enhances both the X-ray
line yield of the He-like argon ion and the ion kinetic energy.
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