[en] Amorphous tantalum oxide (Ta₂O₅) films were deposited on Si substrate for application as the gate dielectric in metal-oxide-semiconductor field-effect transistors (MOSFETs). Prior to Ta₂O₅ deposition, the Si substrate was nitrided in an N₂O+NH₃ plasma at 450 deg. C to form a passive silicon oxynitride (SiO_xN_y) layer. In this work, spectroscopic ellipsometry was used to determine the complex refractive index and the thickness of the SiO_xN_y and Ta₂O₅ layers. To determine the composition of the dielectric stack, the Bruggeman effective medium approximation (EMA) model was applied to each layer for fitting the ellipsometry data. Using X-ray photoelectron spectroscopy (XPS) as a complementary method to verify the film composition and thickness, we have found that the EMA model explains the composition of the two mixed phases (SiO₂ and Si₃N₄) in the SiO_xN_y layer, as well as the off-stoichiometry in the Ta₂O₅ layer

[en] In this work, Cu(50 nm)/Ta(10 nm, or no Ta)/TaN(50 nm)/Ta(10 nm) metallization layers were deposited onto Si or SiO₂/Si substrates by magnetron sputtering. Samples were subsequently annealed at various temperatures ranging from 400 to 800 deg. C in vacuum. The sheet resistance, crystalline microstructure, and surface morphology were investigated by four-point probe, θ-2θ X-ray diffraction, and scanning electron microscopy. Experimental results reveal that Cu films exhibit (111) preferred orientation on Ta but show both (111) and (200) textures on TaN. After annealing, copper films agglomerate on TaN but remain continuous on Ta. However, the Ta layer interposed between Cu and TaN dilutes the nitrogen concentration of the barrier so that reaction between Cu and Si occurs in the Cu/Ta/TaN/Ta/Si system after annealing at 800 deg. C and Cu₃Si forms. In contrast, the Cu/TaN/Ta/Si system shows agglomeration but no reaction up to 800 deg. C. Upon annealing, Cu/TaN/Ta and Cu/Ta/TaN/Ta stacks on a SiO₂/Si substrate exhibit similar crystal structural and morphological evolution to their parallel samples on a Si substrate, except that no Cu-Si reaction is observed for the Cu/Ta/TaN/Ta/SiO₂/Si system after annealing at 800 deg. C. Grain growth behavior of Cu films deposited on different multilayer structures is also discussed

No abstract available

[en] Different composition Fe_xPt_1_−_x films were fabricated on three typical single crystal substrates (MgO, KTaO_3, and SrTiO_3), and the composition-induced strain evolution of Fe_xPt_1_−_x films was systematically investigated. The study showed that different Fe compositions in Fe–Pt films resulted in different strain status and crystallographic textures, and thus influenced the magnetic properties. Under the tensile strain between the Fe–Pt and (MgO, KTaO_3, and SrTiO_3) substrates, Fe–Pt films preferred to form ordered Fe–Pt (001) texture. Decrease of the Fe atom concentration caused the Fe–Pt films to be further relaxed, and an obvious increase of lattice constant c. Moreover, with reducing the mismatch between Fe–Pt and substrate from MgO to KTaO_3 and SrTiO_3, the strain status of Fe–Pt films changed from completely strained to partially relaxed. The perpendicular anisotropy of Fe_5_5Pt_4_5 films grown on STO was larger than that grown on MgO and KTO, which was attributed to better epitaxial quality of the FePt (001) texture induced by less lattice mismatch. - Highlights: • Different Fe compositions in Fe–Pt films resulted in different strain status and crystallographic textures. • Under the tensile strain, Fe–Pt films preferred to form ordered Fe–Pt (001) texture. • Decrease of the Fe atom concentration caused the Fe–Pt films to be further relaxed, and an obvious increase of lattice constant c. • With reducing the mismatch, the strain status of Fe–Pt films changed from completely strained to partially relaxed

[en] L1₀ ordered FePt films of (0 0 1) preferred orientation with different thickness have been prepared by DC magnetron sputtering on CrRu (2 0 0) underlayer. The effect of thin film thickness on the structural and magnetic properties was investigated using X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). Increasing the FePt magnetic layer thickness from 5 to 20 nm resulted in improvement of the superlattice fct-FePt (0 0 1) preferred orientation. However, when the FePt thickness is 40 nm the fct-FePt (0 0 1) preferred orientation began to deteriorate. The degree of long range ordering increases linearly with the FePt layer thickness. Out-of-plane coercivity shows linear relation with thickness only to 20 nm, where a maximum value of 2610 Oe is achieved. The initial growth layer and the intrinsic magnetocrystalline anisotropy are calculated. Initial growth layer thickness was found to be within the range of 2.9-3.5 nm in our films and the intrinsic magnetocrystalline anisotropy ranges from 1.45x10⁷ to 1.91x10⁷ erg/cm³, depending on the demagnetisation factor

[en] L-lysine and its metabolite pipecolic acid (PA) have been studied for their effects on pentylenetetrazol (PTZ)-induced seizures in mice. L-Lysine of L-Pa i.p. significantly increased clonic and tonic latencies in a dose-dependent manner against 90 mg/kg PTZ-induced seizures. L-Lysine but not L-Pa enhanced the anticonvulsant effect of diazepam (DZ). L-Pa i.c.v. showed a slight decrease in clonic latency; it did not enhance the antiseizure activity of DZ; it caused seizures at 0.6 mmol/kg. D-PA i.c.v. displayed an opposite effect compared to its L-isomer. The anticonvulsant effect of L-lysine in terms of increase in seizure latency and survival was even more amplified when tested with a submaximal PTZ concentration. L-Lysine showed an enhancement of specific ³H-flunitrazepam(FZ) binding to mouse brain membranes both in vitro an din vivo. The possibility of L-lysine acting as a modulator for the GABA/benzodiazepine receptors was demonstrated. Since L-PA showed enhancement of ³H-FZ binding only in vitro but not in vivo, the anticonvulsant effect of L-PA may not be linked to the GABA/benzodiazepine receptor

[en] The filtered cathodic vacuum arc technique was employed to deposit magnetic films such as FeNi on silicon substrate. Using the normal cathode design, tetrahedral amorphous carbon and metals films can be deposited. If a magnetic target is used, the arc spot always preferably moves to the edge of the target and then extinguishes. Therefore, the arc is not stable and no film can be deposited. A cathode was designed to obtain stable and continuous arc and uniform erosion pattern. The atomic force microscopy, grazing X-ray diffraction and vibrating sample magnetometry were used to characterize the morphological, structural and magnetic properties of the FeNi film. When the film deposited at substrate bias of -100 V, it exhibits a square magnetization-hysteresis loop, the lowest coercivity and the highest saturated magnetization among all the investigated samples, which may be related to its good surface roughness and crystallinity

[en] A nonmagnetic Ag pinning layer was deposited between two FePt magnetic layers in order to introduce impurities or defects in the interfaces. These inhomogeneities may serve as pinning sites to impede the domain wall motion and thus enhance the coercivity of the magnetic film. The effects of pinning layer on the magnetic properties and magnetization reversal mechanism of FePt perpendicular media were investigated

[en] The feasibility of the determination of phosphorus at the extreme trace levels in high-purity silicon by radioreagent method is explored. After silicon dissolution with hydrofluoric and nitric acids and matrix volatilization, 12-molybdophosphoric acid is formed by the addition of the reagent, sup(99)MoOsub(4)sup(2-), in nitric acid medium and then extracted into isobutyl acetate. By plotting the phosphorus content against the radioactivity of sup(99)Mo in the organic phase, a linear relationship persisting down to 5 ng is obtained. Special effort was made to eliminate the unreacted sup(99)MoOsub(4)sup(2-) reagent and the optimal control of phosphorus blank introduced through the multistage analytical procedure in order to ensure reliable determination of phosphorus at the ppb level. (author)

[en] Nitrogenase is composed of two separately purified proteins, a molybdenum-iron (MoFe) protein and an iron (Fe) protein. Structural genes (nifD and nifK) encoding α and β subunits of the MoFe protein of Clostridium pasteurianum (Cp) have been cloned and sequenced. The deduced amino acid sequences were analyzed for structures that could be related to the unique properties of the Cp protein, particularly its low capacity to form an active enzyme with a heterologous Fe protein. Cp nifK is located immediately downstream from Cp nifD, with the start codon of nifK overlapping by one base with the stop codon of nifD. An open reading frame following nifK was identified as nifE. The amino acid sequence deduced from nifK encompasses the partial amino acid sequences previously reported from the isolated β subunit. Cp nifK encodes a polypeptide of 458 amino acid residues (M/sub r/ 50,115) whose amino-terminal region is about 50 resides shorter than the otherwise conserved corresponding polypeptides from four other organisms. In contrast, Cp α subunit (nifD product) contains an additional stretch of 50 amino acid residues in the 380-430 region, which is unique to the Cp protein. It therefore appears that the combined size of the α and β subunits could be important to nitrogenase function. An analysis of the predicted secondary structure from the amino acid sequence of each subunit from three species (C. pasteurianum, Azotobacter vinelandii, and Rhizobium japonicum) further revealed structural features, including regions adjacent to some of the conserved cysteine resides, differentiating the Cp MoFe protein from others. These different regions may be further tested for correlation with distinct properties of Cp nitrogenase