Numerical analysis for the dynamics of the oxidation-induced stacking fault in czochralski-grown silicon crystals

The continuum model of point defect dynamics to predict the concentration of interstitial and vacancy is established by estimating expressions for the thermophysical properties of point defects and the point defect distribution in a silicon crystal and the position of oxidation-induced stacking fault ring (R-OiSF) created during the cooling of crystals in Czochralski silicon growth process are calculated by using the finite element analysis. Temperature distributions in the silicon crystal in an industrial Czochralski growth configuration are measured and compared with finite volume simulation results. These temperature fields obtained from finite volume analysis are used as input data for the calculation of point defect distribution and R-OiSF position. Calculations of continuum point defect distributions predict the transition between vacancy and interstitial dominated precipitations of microdefects as a function of crystal pull rate (V). The dependence of the radius of R-OiSF (R_OiSF) on the crystal length with fixed growth rate for a given hot zone configuration is examined. The R_OiSF is increased with the increase of crystal length. These predictions from point defect dynamics are well agreed with experiments and empirical V/G correlation qualitatively, where G. is the axial temperature gradient at the melt/crystal interface.     

Silicon–Carbon Stressors With High Substitutional Carbon Concentration and In Situ Doping Formed in Source/Drain Extensions of n-Channel Transistors

We report the first demonstration of n-channel field-effect transistors (N-FETs) with in situ phosphorus-doped silicon-carbon (SiCP) stressors incorporated in the source/drain extension (SDE) regions. A novel process which formed recessed SDE regions followed by selective epitaxy of SiCP was adopted. High in situ doping contributes to low series resistance to channel resistance ratio and is important for reaping the benefits of strain. Substitutional carbon concentration was varied, showing enhanced drive current with increased for comparable off-state leakage, series resistance, and control of short-channel effects. A record high carbon substitutional concentration of 2.1% was achieved. Use of heavily doped silicon-carbon stressor with large lattice mismatch with respect to Si and placed in close proximity to the channel region in the SDE regions is expected to be important for strain engineering in nanoscale N-FETs.     

Microstructure and Tensile Properties of Sn-1Ag-0.5Cu Solder Alloy Bearing Al for Electronics Applications

This work investigates the effects of 0.1?wt.% and 0.5?wt.% Al additions on bulk alloy microstructure and tensile properties as well as on the thermal behavior of Sn-1Ag-0.5Cu (SAC105) lead-free solder alloy. The addition of 0.1?wt.% Al reduces the amount of Ag₃Sn intermetallic compound (IMC) particles and leads to the formation of larger ternary Sn-Ag-Al IMC particles. However, the addition of 0.5?wt.% Al suppresses the formation of Ag₃Sn IMC particles and leads to a large amount of fine Al-Ag IMC particles. Moreover, both 0.1?wt.% and 0.5?wt.% Al additions suppress the formation of Cu₆Sn₅ IMC particles and lead to the formation of larger Al-Cu IMC particles. The 0.1?wt.% Al-added solder shows a microstructure with coarse ??-Sn dendrites. However, the addition of 0.5?wt.% Al has a great effect on suppressing the undercooling and refinement of the ??-Sn dendrites. In addition to coarse ??-Sn dendrites, the formation of large Sn-Ag-Al and Al-Cu IMC particles significantly reduces the elastic modulus and yield strength for the SAC105 alloy containing 0.1?wt.% Al. On the other hand, the fine ??-Sn dendrite and the second-phase dispersion strengthening mechanism through the formation of fine Al-Ag IMC particles significantly increases the elastic modulus and yield strength of the SAC105 alloy containing 0.5?wt.% Al. Moreover, both 0.1?wt.% and 0.5?wt.% Al additions worsen the elongation. However, the reduction in elongation is much stronger, and brittle fracture occurs instead of ductile fracture, with 0.5?wt.% Al addition. The two additions of Al increase both solidus and liquidus temperatures. With 0.5?wt.% Al addition the pasty range is significantly reduced and the differential scanning calorimetry (DSC) endotherm curve gradually shifts from a dual to a single endothermic peak.     

The validity of self-reported seatbelt use in a country where levels of use are low

The validity of self-reported seatbelt use among low belt use populations in low belt use countries has not been evaluated directly. Nine hundred and ninety drivers were recruited from shopping centers, car parks, and other suitable locations located in Afyon and Ankara cities of Turkey in order to compare the self-reported and observed seatbelt usage rates. Data sets were collected simultaneously from the participants not being aware of having their seatbelt use observed. Participants interviewed in Afyon (n = 301) and Ankara (n = 658) reported seatbelt usage (“always using a seatbelt”) rates of 39% and 45%, respectively. When observed, however, only 47% in Afyon and 70% in Ankara of these drivers actually fasten their seat-belts. It seems that the drivers in both cities exaggerated their use seat belts considerably.     

Identification of low-abundance cancer biomarker candidate TIMP1 from serum with lectin fractionation and peptide affinity enrichment by ultrahigh-resolution mass spectrometry

As investigating a proteolytic target peptide originating from the tissue inhibitor of metalloproteinase 1 (TIMP1) known to be aberrantly glycosylated in patients with colorectal cancer (CRC), we first confirmed that TIMP1 is to be a CRC biomarker candidate in human serum. For this, we utilized matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) showing ultrahigh-resolution and high mass accuracy. This investigation used phytohemagglutinin-L(4) (L-PHA) lectin, which shows binding affinity to the β-1,6-N-acetylglucosamine moiety of N-linked glycan on a protein, to compare fractionated aberrant protein glycoforms from both noncancerous control and CRC serum. Each lectin-captured fraction containing aberrant glycoforms of TIMP1 was digested by trypsin, resulting in the tryptic target peptide, representative of the serum glycoprotein TIMP1. The resulting target peptide was enriched using a stable isotope standard and capture by the antipeptide antibody (SISCAPA) technique and analyzed by a 15 T MALDI FTICR mass spectrometer with high mass accuracy (Δ < 0.5 ppm to the theoretical mass value of the target peptide). Since exact measurement of multiplex isotopic peaks of the target peptide could be accomplished by virtue of high mass resolution (Rs > 400,000), robust identification of the target peptide is only achievable with 15 T FTICR MS. Also, MALDI data obtained in this study showed that the L-PHA-captured glycoforms of TIMP1 were measured in the pooled CRC serum with about 5 times higher abundance than that in the noncancerous serum, and were further proved by MRM mass analysis. These results confirm that TIMP1 in human serum is a potent CRC biomarker candidate, demonstrating that ultrahigh-resolution MS can be a powerful tool toward identifying and verifying potential protein biomarker candidates.     

Synthesis of fluorene-based semiconducting copolymers for organic solar cells

Semiconducting polymers composed of 2,2'-(9,9-dioctyl-9H-fluorene-2,7-diyl)dithiophenes (F8T2s) and (2E,2'E)-3,3'-(2,5-bis(octyloxy)-1,4-phenylene) bis(2-(5-bromothiophene-2-yl)acrylonitrile)s (OPTANs) have been synthesized through Pd(O)-catalyzed Suzuki coupling polymerization by controlling the monomer ratio. The synthesized polymers were confirmed to exhibit good solubility in common solvents, simple processability, and thermal stability up to 350 degrees C. The highest occupied molecular orbitals (HOMOs), lowest unoccupied molecular orbitals (LUMOs), and optical band-gap energies were determined using cyclic voltammetry (CV) and UV-visible spectrometry. The synthesized polymers showed their maximum absorption and edge at around 520 and 650 nm, respectively. The optical band-gap energies of the polymers were determined to be 1.89 eV. Bulk heterojunction organic solar cells were fabricated using the conjugated polymer as the electron donor, and 6,6-phenyl C61-butyric acid methylester (PC61BM) or 6,6-phenyl C71-butyric acid methylester (PC71BM) as the electron acceptor. The power conversion efficiencies (PCEs) of the solar cells based on polymer:PC71BM (1:1) and polymer:PC71BM (1:2) were 0.68% and 1.22%, respectively, under air mass 1.5 global (AM 1.5 G) illumination at 100 mW/cm2.     

Hydrogel nanoparticles with covalently linked coomassie blue for brain tumor delineation visible to the surgeon

Delineation of tumor margins is a critical and challenging objective during brain cancer surgery. A tumor-targeting deep-blue nanoparticle-based visible contrast agent is described, which, for the first time, offers in vivo tumor-specific visible color staining. This technology thus enables color-guided tumor resection in real time, with no need for extra equipment or special lighting conditions. The visual contrast agent consists of polyacrylamide nanoparticles covalently linked to Coomassie Blue molecules (for nonleachable blue color contrast), which are surface-conjugated with polyethylene glycol and F3 peptides for efficient in vivo circulation and tumor targeting, respectively.     

Conversion mechanism of nickel fluoride and NiO-doped nickel fluoride in Li ion batteries

The conversion mechanism of NiF₂ and NiO-doped NiF₂ during electrochemical cycling was investigated using a combination of structural analysis by ex situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and magnetic analysis by superconducting quantum interference device (SQUID) magnetometry. It was observed that the conversion reactions in both cathode materials were partially reversible; however, they differ in their conversion rate. NiO-doped NiF₂ exhibited enhanced electrochemical properties in terms of the conversion potential and reversibility due to the presence of a NiO phase, which has slightly higher electronic conductivity than NiF₂. It is suggested that the NiO doping reduced the nucleation sites for Ni nanoparticles, subsequently enhancing the kinetics of the conversion reaction involving the growth of Ni particles formed during lithiation. The ex situ XRD and the magnetic hysteresis data (H_C and M_S) indicate that the average dimension of the Ni particles formed along with LiF in pristine NiF₂ and NiO-doped NiF₂ during the 1st lithiation was in the superparamagnetic regime, with 4–5 nm and 8–9 nm particle sizes, respectively. Although the particle size was decreased to the nanoscale, the original NiF₂ phase was regenerated by re-lithiation.     

Failure Analysis of Modular-Block Reinforced-Soil Walls during Earthquakes

Several modular-block reinforced-soil retaining walls failed during the 1999 Ji-Ji (Chi-chi) earthquake of Taiwan. Similar walls showed distress during the 1994 Northridge, Calif., earthquake. The instability or failure of these walls offered an opportunity to validate the simplistic pseudostatic limit-equilibrium procedures. In this study, the Ta Kung Wall of the Ji-Ji earthquake is analyzed, and the Gould and Valencia Walls of the Northridge earthquake are revisited with an improved estimation of local site acceleration. The local acceleration was estimated by using simple attenuation relationships obtained through the earthquake records. The results of analysis indicate that these three walls had adequate internal stability under estimated site acceleration. The geosynthetic length was inadequate to resist compound modes of failure where the potential failure surface extends beyond the reinforced zone. The external stability was most critical in the presence of horizontal and vertical accelerations.