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Previous dual-frequency lasers mainly made use of artificial birefringence for frequency splitting, which were of a limited-frequency difference stability and complex construction. In this paper, we invented a novel Zeeman-birefringence He-Ne dual-frequency laser without any artificial devices, but by hole drilling in the cavity mirror. The laser-frequency difference (LFD) ranging from kilohertz to tens of megahertz was realized and the relationship between the LFD and the hole geometric sizes was investigated. Theoretical analyses were carried out. Characteristics of the LFD were explored for both the indium-sealed and hard-sealed lasers with a frequency stabilization system. The results showed the LFD with hole-drilling, indium-sealed lasers is maintained at 30 kHz within 2 h, which is better than the hard-sealed ones with a stability of 200 kHz within 2 h. The hole-drilling Zeeman-birefringence He-Ne lasers may make significant progress for the light source of the interferometers and Doppler velocimeters.

Summary Aim: CYP1A2, a constitutive enzyme expressed in the liver, is among the phase I enzymes responsible for polycyclic aromatic hydrocarbons metabolism. Phenacetin O-de-ethylation is a marker for CYP1A2 activity. This study investiagtes the metabolism of phenacetin in patients with hepatocellular carcinoma (HCC). Methods: The phenacetin test was performed in 56 normal subjects and 92 HCC patients. The test was repeated in HCC patients after treatment with transcatheter arterial chemoembolization (TACE). The recovery of phenacetin’s urinary metabolites was studies in 12 normal subjects and 14 patients with HCC. Results: Compared with normal controls, the recovery of phenacetin O-de-ethylated metabolites decreased by 42·5% (P

The corrosion and protection characteristics of phosphate coatings formed in a phosphating solution containing mainly ZnO, H3PO4 and NaF, using Y2O3 as an additive, were investigated through SEM, polarisation curves and EIS diagrams. The results show that the corrosion protection of phosphate coatings has been improved when Y2O3 is added to the phosphating solution, making the free corrosion potential shift to the positive direction and causing the corrosion current to decrease. The protection ability of phosphate coatings depends mainly on their barrier performance. The phosphate coatings formed in the phosphating solution with 10 and 20 mg L–1 Y2O3 have finer crystal structures and smaller porosity; therefore, they exhibit better corrosion resistance and adhesion properties than those without Y2O3 and with 40 mg L–1 Y2O3.

Self-incompatibility (SI) has been studied extensively at the molecular level in Solanaceae, Rosaceae and Scrophulariaceae, all of which exhibit gametophytic self-incompatibility (GSI). In the present study, four PpsS-haplotypes (Prunus pseudocerasus S-haplotypes) comprising at least two genes, i.e., PpsS-RNase (P. pseudocerasus S-RNase) and PpsSFB (P. pseudocerasus S-haplotype-specific F-box) have been successfully isolated in tetraploid P. pseudocerasus Lindl. CV. Nanjing Chuisi ("NC") which exhibited self-compatibility (SC), and its S-genotype was determined as S-1/S-3'/S-5/S-7. These PpsS-RNases, which were expressed exclusively in style, shared the typical structural features with S-RNases from other Prunus species exhibiting GSI. All PpsSFBs showed similar structure characteristics of SFBs from other Prunus species, and matched with the necessary conditions for pollen S-determinant. No mutations leading to dysfunction of S-haplotype were found in their full-length c-DNA sequences, except for PpsS-3'-haplotype which was not amplified by PCR. These four S-haplotypes complied with tetrasomic inheritance. Diploid pollen grains with S-genotypes S-7/S-1, S-7/S-5 and S-1/S-5 can grow the full length of the style after self-pollination, while pollen grains with S-3'/S-7, S-3'/S-1 and S-3'/S-5 cannot. These results suggest that PpsS-haplotypes-1, -5 and -7 are functional, and that competitive interaction between two of them confer self-compatibility on cultivar "NC". Furthermore, in terms of recognition specificity, diploid pollen grains carrying PpsS-3'-haplotype are equal to monoploid pollen grains carrying the other functional S-haplotype.

The corrosion and protection characteristics of phosphate coatings formed on aluminum alloy (AA)6061 (UNS A96061) in a phosphating solution containing mainly zinc oxide (ZnO), phosphoric acid (H3PO4), and sodium fluoride (NaF), using yttrium oxide (Y2O3) as additive, were investigated through scanning electron microscopy (SEM), polarization curves, electrochemical impedance spectroscopy (EIS) diagrams, the salt water immersion test, and the adhesion test. The results show that the corrosion and protection of phosphate coatings have been improved when Y2O3 is added to the phosphating solution, making the free corrosion potential shift to the positive direction and corrosion current to decrease. The phosphate coatings formed in the phosphating solution with 10 mg/L and 20 mg/L Y2O3 have finer crystal structures, and they exhibit better corrosion resistance and adhesion than those with 0 or 40 mg/L Y2O3.

SummaryChinese pear (Pyrus spp.) exhibits gametophytic self-incompatibility (GSI), as do other fruit species in the family Rosaceae. This work determined S-locus diversity in 20 native Chinese pear cultivars or wild accessions using polymerase chain reaction (PCR) and pollination experiments. After cloning and sequencing the PCR products, the S-genotypes of all 20 pear cultivars or wild accessions were determined. Subsequent sequence analysis showed that P. sinkiangensis Yu ‘Aolian’ (SpS32), P. phaeocarpa Rehd. ‘Diaodan’ (SdSe), P. xerophila Yu ‘Shageda’ (S36Sd) and ‘Xingyeli’ (S22Sc), originating in China, shared some S-RNase genes with P. communis, providing evidence that oriental and occidental Pyrus species may share the same pool of alleles at the S-locus. Two novel S-RNase genes were also discovered in P. ussuriensis ‘Maili’ and ‘Neimenggushanli’, and deposited as S40 and S41, under the accession numbers DQ903313 and DQ988687, respectively. Their deduced amino acid sequences showed high similarity t...

SummaryPrunus mume (Japanese apricot) cultivars are self-incompatible and orchards require pollinator cultivars to guarantee optimal fruit production. Identification of the self-incompatibility (S) genotypes of P. mume cultivars is therefore useful for choosing pollinators and for breeding. To elucidate the S-genotypes of eleven Chinese and one introduced cultivar, PCR was performed with primers amplifying the variable second intron of the S-RNase gene. The S-genotyping results were as follows: S4S12 for ‘Dantaofen’; S3S4 for ‘Duoezhusha’; S12S13 for ‘Fubantiaozhi’; S15S16 for ‘Hongding’; S13S14 for ‘Longyanmei’; S5S11 for ‘Musashino’; S10S14 for ‘Xiaoyezhugan’; and S3S15 for ‘Qingfeng’,‘Qingjia’, ‘Xiyeqing’, ‘Dayeqing’ and ‘Changnong 17’. We identified seven new S-RNase alleles, S10-RNase to S16-RNase, deposited in GenBank under the accession numbers: DQ011150, DQ201191, DQ201192, DQ345781, DQ768219, DQ903312 and EF990750, respectively.

SummaryPolymerase chain reaction (PCR) was conducted with Prunus S-RNase gene-specific primers on 17 Chinese cultivars of Japanese plum (Prunus salicina Lindl.). These primers were designed from the conserved regions of Prunus S-RNase genes. Each cultivar produced two amplicons, apart from two cultivars that had three amplicons. In all, 36 amplicons were cloned and sequenced. Analysis of these sequences revealed 13 novel S-alleles, the amino acid sequences of which showed 62% (S15 vs. S19) to 92% (S22 vs. S24) identity. The sequences also demonstrated several typical structural features of Prunus S-RNase genes: three conserved regions (C1, C2 and C3), one hypervariable region (RHV) with one intron, and another intron located at the junction between the signal peptide and the mature protein. Compared to S2 from apricot, S26 from Japanese plum had only two nucleotide substitutions in the exon region, which resulted in only one amino acid residue difference in the signal peptide. However, there were large nu...

In this study, we optimized a restriction-ligation-free (RLF) method to save time and cost of constructing multiple plasmids with the same gene insert, and examined the efficacy of RLF on high-throughput multi-plasmid cloning. This method utilizes the precise DNA repair and recombination systems within Escherichia coli, which allows to bypass the in vitro restriction and ligation enzyme reactions commonly included in routine cloning procedures. A homologous arm is linked to the 5'-end of the forward primer used to amplify both the target gene and vector. A different homologous arm is linked to the 5'-end of the reverse primer. Therefore, genes can be cloned into the vectors by homologous recombination after co-transformation of the amplified target gene and the linearized vector, which bear the same homologous arm on either end. More than twenty-four different plasmids were generated by this method, which uses two simple polymerase chain reaction steps. This method is highly efficient in cloning any gene of interest into any vector at any site without sequence constraints, as no restriction and ligation reactions are required.

In a bilayer consisting of an insulator (I) and a ferromagnetic metal (FM), interfacial spin orbit scattering leads to spin mixing of the two conducting channels of the FM, which results in an unconventional anisotropic magnetoresistance (AMR). We theoretically investigate the magnetotransport in such bilayer structures by solving the spinor Boltzmann transport equation with generalized Fuchs-Sondheimer boundary condition that takes into account the effect of spin orbit scattering at the interface. We find that the new AMR exhibits a peculiar angular dependence which can serve as a genuine experimental signature. We also determine the dependence of the AMR on film thickness as well as spin polarization of the FM., 6 pages, 3 figures

Breaking the time-reversal symmetry (TRS) in topological insulators (TIs) through ferromagnetic doping is an essential prerequisite for unlocking novel physical phenomena and exploring potential device applications. Here, we report the successful growth of high-quality (Dy(x)Bi(1-x))2Te3 thin films with Dy concentrations up to x = 0.355 by molecular beam epitaxy. Bulk-sensitive magnetisation studies using superconducting quantum interference device magnetometry find paramagnetic behaviour down to 2 K for the entire doping series. The effective magnetic moment, μeff, is strongly doping concentration-dependent and reduces from ∼12.6 μ(B) Dy(-1) for x = 0.023 to ∼4.3 μ(B) Dy(-1) for x = 0.355. X-ray absorption spectra and x-ray magnetic circular dichroism (XMCD) at the Dy M4,5 edge are employed to provide a deeper insight into the magnetic nature of the Dy(3+)-doped films. XMCD, measured in surface-sensitive total-electron-yield detection, gives μ(eff )= 4.2 μ(B) Dy(-1). The large measured moments make Dy-doped films interesting TI systems in which the TRS may be broken via the proximity effect due to an adjacent ferromagnetic insulator.

Ovarian cancer is the third most common cancer in female reproductive system. But ovarian cancer is hard to detect at early phase. It is very urgent to develop effective early diagnosis method for ovarian cancer. RASSF1A (Ras association domain family 1 isoform A) is a tumor suppressor, which modulates multiple apoptotic and cell cycle checkpoint pathways. We amed to find out the relationship between RASSF1A and ovarian cancer.We compared the expressions of RASSF1A gene in different ovarian cancer cell lines, and also in epithelial ovarian cancer tissues and normal ovarian tissues through RT-PCR (reverse transcription polymerase chain reaction) technique.RASSF1A was expressed in HO8910 and HO8910PM cells, while RASSF1A mRNA was absent in SKOV-3 and OVCAR-3 cells. RASSF1A was expressed in 10 normal ovarian tissue samples (10/10, 100%), while RASSF1A was only expressed in 2 ovarian cancers tissue samples (2/47, 4.3%). The difference in the frequency was significant in tissue samples (100% vs. 4.3%, p0.05).RASSF1A could be served as a potential molecular marker for diagnosing ovarian cancer at early phase.

Self-incompatibility has been studied extensively at the molecular level in Solanaceae, Rosaceae and Scrophulariaceae, all of which exhibit gametophytic self-incompatibility controlled by a single polymorphic locus containing at least two linked genes, i.e., the S-RNase gene and the pollen-expressed SFB/SLF (S-haplotype-specific F-box/S-locus F-box) gene. However, the SFB gene in Japanese plum (Prunus salicina Lindl.) has not yet been identified. We determined eight novel sequences homologous to the SFB genes of other Prunus species and named these sequences PsSFB. The gene structure of the SFB genes and the characteristic domains in deduced amino acid sequences were conserved. Three sequences from 410 to 2,800 bp of the intergenic region between the PsSFB sequences and the S-RNase alleles were obtained. The eight identified PsSFB sequences showed S-haplotype-specific polymorphism, with 74–83% amino acid identity. These alleles were exclusively expressed in the pollen. These results suggest that the PsSFB alleles are the pollen S-determinants of GSI in Japanese plum.

This paper, presents a robust spacer technology for definition of deca-nanometer gate length MOSFETs. Conformal deposition, selective anisotropic dry-etching and selective removal of sacrificial layers enabled patterning of an oxide hard mask with deca-nanometer lines combined with structures defined with I-line lithography on a wafer. The spacer gate technology produces negligible topographies on the hard mask and no residual particles could be detected on the wafer. The line-width roughness of 40nm poly-Si gate lines was 4nm and the conductance of 200@mm long lines exhibited a standard deviation of 6% across a wafer. nMOSFETs with 45nm gate length exhibited controlled short-channel effects and the average maximum transconductance in saturation was 449@mS/@mm with a standard deviation of 3.7% across a wafer. The devices exhibited a cut-off frequency above 100GHz at a drain current of 315@mA/@mm. The physical and electrical results show that the employed spacer gate technology is robust and can define deca-nanometer nMOSFETs with high yield and good uniformity.

Ni-salicided MOSFETs with a gate stack of ALD Al2O3/HfO2/Al2O3 high-x dielectric and poly-SiGe gate electrode were fabricated. The Si pMOSFETs with an EOT of 1.7 nm showed an expected gate leakage ...

Low-frequency noise was characterized in Si0.7Ge0.3 surface channel pMOSFETs with ALD Al2O3/HfO2/Al2O3 stacks as gate dielectrics. The influences of surface treatment prior to ALD processing and ...

The Ni-based self-aligned silicide process has attracted a rapidly growing interest for contact metallization in Si technology, as the device dimensions are scaled down into the sub-100 nm regime. Incorporation of Ge in the electrodes of a MOSFET, i.e. gate and source/drain, in order to further enhance device performance, has made the study of Ni-Si1-xGex interactions a scientifically and technologically important issue. Among the different germanosilicides of Ni, NiSi1-uGeu (i.e. mono-germanosilicide, with u possibly different from x in the Si1-xGex) is the most desirable phase due to its low specific resistivity of 12-25 µΩcm. The focus of the present work is placed on issues concerning the phase and morphology stability of NiSi1-uGeu on single-crystal and polycrystalline Si1-xGex substrates. The related experimental data from our recent work are analysed with reference to two classics on the formation of silicides by d'Heurle [J. Mater. Res. 3 (1988) 167] and by d'Heurle and Gas [J. Mater. Res. 1 (1986) 205]. Influences of C and Pt on the stability of NiSi1-uGeu are also covered. The electrical properties of the NiSi1-uGeu-Si1-xGex contact are discussed referring to our latest experimental results.

Expressions for the directional dependence of Young's modulus and Poisson's ratio were derived for a general material under plane-stress conditions. Experiments with a laser extensometer to measure the Young's modulus and Poisson's ratio directly by a tension test are described, and the results are compared with the theoretical expressions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 260–266, 2004

Scratch testing has been performed on elastomeric poly(dimethylsiloxane) (PDMS) coatings on stainless steel with a spherical indenter. The friction coefficient (horizontal-to-normal force ratio) during scratching decreases with increasing normal load. This result can be explained by assuming that during scratching the contact area is determined by elastic deformation and the horizontal force is proportional to the contact area. With increasing driving speed, the friction coefficient increases, but the rate of increase decreases; this suggests that the scratching of the PDMS coating is a rate process and that the viscoelastic property of the coating influences its frictional behavior. Below a critical normal load, which increases with the coating thickness, the PDMS coating recovers elastically after being scratched so that there are no scratch marks left behind. Above the critical normal load, the coating is damaged by a combination of delamination at the coating/substrate interface and through-thickness cracking. When the coating is damaged, there is an increase in the friction coefficient, and the friction force displays significant fluctuations. Furthermore, the critical normal load increases with the driving speed; this implies that time is needed to nucleate damage. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1530–1537, 2002

Scratch testing was performed on poly(n-butyl acrylate) (PnBA) films with a sapphire indenter with a spherical tip (76 μm in radius). For uncrosslinked PnBA film, the surface of which is sticky, the horizontal or scratching force decreases with decreasing normal load and has a residual value (∼ 6 mN) as the normal load approaches zero. The relation between the scratching force and normal load can be understood by finite element computation based on the Johnson–Kendall–Roberts theory under the assumption that the scratching force is proportional to the contact area, which depends on the normal load. With increasing driving speed, the scratching force shows a power relation with speed indicating a rate process. For crosslinked PnBA film, which behaves as an elastomer, the horizontal force approaches zero at zero normal load. Below a critical normal load, which depends on the thickness of the film, the crosslinked film recovers elastically after being scratched. Above the critical load, the film is damaged and, depending on its thickness, shows two distinct damage mechanisms. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 585–592, 2002; DOI 10.1002/polb.10117

The formation of titanium disilicide (TiSi2) from Ti deposited using ionized metal plasma under different deposition conditions has been investigated. It is shown that deposition at elevated substrate temperature (450°C) enhances the formation of the low-resistivity C54 TiSi2, especially in patterned narrow lines. Grain-boundary footprint pictures obtained by atomic force microscopy indicate a larger grain-size distribution for the films deposited at higher substrate temperature. Deposition under substrate bias resulted in reduced contact resistivity. However, the use of substrate bias results in increased probability of bridging of silicide over the isolating spacers.

The stick–slip process and temperature effect in scratch testing of materials have been studied. For a poly(methyl methacrylate) (PMMA) polymer scratched by a conical diamond indenter, both the amplitude and period of the stick–slip at room temperature increase with the normal load and decrease with the driving speed. An increase in temperature leads to an increase in stick–slip amplitude and period, as well as in the average horizontal force. For bismuth metal scratched by a conical tungsten indenter, the surface temperature in the contact area reveals fluctuations related to the stick–slip motion.

Several samples collected from lakes, rivers and reservoirs in Haihe river basin of China were analyzed for 8 sulfonamide antibiotics by using solid-phase extraction and liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). All water samples were enriched with HLB extraction cartridges. The antibiotics were separated by gradient elution with methanol as the mobile phase adding 0.1% formic acid. The eluate was then analyzed by the mode of multiple reaction monitoring (MRM). The limits of detection (LOD) and quantification (LOQ) were 0.4-1.0 ng/L and 1.0-3.0 ng/L respectively. The method was used for the analysis of 13 samples from Haihe river basin in China. The results showed that sulfamethoxazole was present in all water samples with maximum concentration of 107.59 ng/L. Sulfadiazine was also frequently detected, concentrations ranging from 2.81 ng/L to 85.35 ng/L. Other sulfonamide antibiotics were not detected in most water samples, especially for those samples from drinking water resources.

The temporal and spatial distribution of PAHs in surface-water from the typical rivers of North China was investigated. PAHs in typical rivers ranged from n.d. to 1.98 ng/L. LMW PAHs (2 and 3-ring) were abundant in surface water with high detection frequencies in Beisanhe River, while HMW PAHs (4 and 6-ring) were abundant in Luanhe River. Specific PAHs with its ratios were measured in order to deduce the possible sources of PAHs contaminant. The results indicate that the PAHs were from combustion processes in Beisanhe River, while PAHs were from petroleum products in Luanhe River.

Using comprehensive density functional theory calculations, the structural, electronic, and optical properties of novel fluorosilicene/chlorosilicene (F-silicene/Cl-silicene) heterobilayer are investigated. Our results unveil that the presence of hetero-halogen bonding (Si-F···Cl-Si) has a remarkable influence on the F-silicene/Cl-silicene bilayer. The F-silicene/Cl-silicene heterostructure in the most stable pattern has a moderate band gap of 0.309 eV, lower than that of isolated halogenated silicene. Encouragingly, F-silicene/Cl-silicene heterobilayers all have a direct band gap nature, irrespective of the stacking pattern, thickness and external electric fields (E-fields), which is an advantage over MoS2 layers. In addition, applying appropriate E-field leads to a significant enhancement of binding strength of the F-silicene/Cl-silicene heterobilayer. Especially, the band gap of the F-silicene/Cl-silicene heterobilayer can be effectively modulated by E-fields, even a semiconductor–metal transition occu...

Using first-principles density functional theory calculations, we investigate the structure, stability, optical modes and electronic band gap of a distorted tetragonal MoS$_2$ monolayer (T'-MoS$_2$). Our simulated scanning tunnel microscopy (STM) images of T'-MoS$_2$ are dramatically similar with those STM images which were identified as K$_{x}$(H$_{2}$O)$_{y}$MoS$_{2}$ from a previous experimental study. This similarity suggests that T'-MoS$_2$ might have already been observed in experiment but was unexpectedly misidentified. Furthermore, we verify the stability of T'-MoS$_2$ from thermal, mechanical and dynamic aspects, by \emph{ab initio} molecular dynamics simulation, elastic constants evaluation and phonon band structure calculation based on density functional perturbation theory, respectively. In addition, we calculate the eigenfrequencies and eigenvectors of the optical modes of T'-MoS$_2$ at $\Gamma$ point and distinguish their Raman and infrared activity by pointing out their irreducible representations using group theory; at the same time, we compare the Raman modes of T'-MoS$_2$ with those of H-MoS$_2$ and T-MoS$_2$. Our results provide a useful guidance for further experimental identification and characterization of T'-MoS$_2$., Comment: 10 pages, 12 figures, 3 tables

In situ sheet resistance measurements were used to study copper films alloyed with various concentrations of cobalt during annealing at temperatures up to 1000°C. The films were initially characterized by a high resistivity, several times that of pure copper, because of the presence of cobalt dissolved in copper. A large decrease in resistance, that occurs when the temperature reaches 100–150°C, is likely to be the consequence of the precipitation of cobalt associated with grain growth in the copper film. In this process, the free energy change that accompanies precipitation is added to the usual driving force that causes grain growth, namely, the overall decrease in interface energy. An activation energy of approximately 1 eV was found by varying the ramp rates during in situ resistance analysis, indicating the dominance of grain boundary diffusion. Further increases in temperature led to other changes in resistance that can be attributed to precipitate dissolution, and the reaction of cobalt with a tantalum adhesion layer. The activation energy of approximately 2 eV determined for this latter reaction is characteristic of the lattice diffusion of cobalt in copper. A rather extensive discussion considers (a) the modalities of the resistance changes that may be observed during heating and cooling solid solution alloys; and (b) the use that can be made of these changes to determine such process characteristics as activation energies.

This paper examines high-speed interconnection design in 0.1 μm technology from a simulation and modelling perspective. It is shown that using Cu metallisation in combination with a low- e dielectric can reduce the minimum delay considerably, as compared to using Al metallisation with SiO 2 as the inter-metal dielectric. Consequently, the use of Cu and a low- e dielectric leads to substantial saving of the surface area for buffers that are necessary to incorporate in order to maintain the improved performance when scaling down the device dimensions. As regard to buffer design and insertion, it is a good choice to allow the size of the cascaded inverters in each buffer to increase successively, and simultaneously to permit the size-ratio of two consecutive inverters to increase along the signal propagation direction in order to minimise power consumption and delay. Furthermore, in order to save the precious Si surface area, it is preferable not to drive an interconnection line at a speed unnecessarily higher than the specified speed. Therefore, in parallel with the search for better conductors and insulators as well as improved interconnection technologies, there is an urgent need to address the interconnection issue from the circuit design perspective.

The electrical behavior during annealing of copper films with a nominal concentration of 2 at.% boron has been investigated. The evolution of the resistivity of the film was monitored using an in situ technique, in which the film was rampannealed at constant ramp rates. At temperature of 150–200°C, the resistivity of the Cu(B) undergoes a first drop. This is followed by one or two such drops in resistivity, so that after completion of a ramp-anneal from 50°C to 750°C, the room temperature resistivity decreases from the initial value of 13 μΩ cm to 2.1 μΩcm, close to that of bulk copper. Isothermal annealing of the film also leads to substantial decreases in resistivity, from 13 μΩcm to 3 μΩ cm after annealing at 350°C for 8 h and to 2.5 μΩ cm at 400°C for 4 h. These results show that a dramatic reduction in resistivity of Cu(B) alloys takes place at temperatures below 400°C, suggesting possible applications for silicon device interconnections.

We observed a violation of the normal Raman selection rule in the resonant Raman spectra of interface (IF) phonon modes of the ultrathin (GaAs)4/(AlAs)2 superlattice. Contrary to the prediction of conventional theories, all four IF modes were observed in both (XX) and (XY) geometries. The result can be interpreted as a consequence of the deep penetration of the electron wave function in the GaAs wells into the AlAs barriers and a lack of definite parity of the electron wave function. Furthermore, our result indicates that conventional theory for bulk (thicker) systems may need to be modified and further developed to be applicable to ultrathin systems.

Threshold voltage control for PMOSFETs using an undoped epitaxial Si channel and a p+-SixGe1-x gate

Fourier transform (FT)-Raman and dispersive, visible excitation Raman spectra are reported for standard solutions and highly colored industrial metal refining solutions containing sulfur oxyanions, primarily sulfate and sulfamate. Good-quality spectra are obtained for both standard and industrial solutions. However, quantitation of both sulfur oxyanion concentrations is complicated by self-absorption effects. In the FT-Raman spectra, self-absorption of the incident laser beam yields an exponential correlation between Raman peak intensity, directly proportional to the apparent sulfate concentration, and the actual sulfate concentration. An internal standard, dispersive Raman spectroscopy, and excitation at 647 nm were used in an attempt to apply a self-absorption correction for absorption of the incident laser beam by ratioing the relative Raman intensities of the standard and species of interest. This approach improves the accuracy for sulfate and sulfamate determination to ±6.1% and ±3.4%, respectively. This study represents the most detailed characterization presented so far of the errors expected in quantitative Raman spectroscopy of industrial solutions. These results suggest that Raman spectroscopy is a uniquely powerful technique for the qualitative and quantitative characterization of industrial metal refining solutions.

Time-dependent (TD) quantum dynamics calculation for the title reaction has been carried out in full mathematical (six) dimensions on a new potential energy surface (denoted TSH3). Our numerical calculation shows that as far as total reaction probabilities and cross sections are concerned, the CN vibration behaves like a spectator bond when both reagents are at ground vibrational state. The vibrational excitation of CN slightly decreases the reaction probability and cross section while vibrational excitation of H2 considerably enhances the reaction probability and cross section. The reaction probability is enhanced by excitations of H2 rotation and more so of CN rotation. Overall, the reaction proceeds by a direct abstraction path without contribution from the insertion process. Comparison of our calculated rate constant with experimental measurements indicates that the effective barrier of the TSH3 PES for the title reaction is perhaps too high by about 0.3 kcal/mol.

The mechanical properties of chemical vapour deposited tungsten (W-CVD) on Ti/TiN adhesion bilayers have been studied. Rapid thermal annealing (RTA) of the Ti/TiN bilayers has been found to strongly affect subsequently deposited W films. The stress in W is reduced as a consequence of the RTA treatment of Ti/TiN, and the stress reduction is especially pronounced for thin W films. However, the stress in the Ti/TiN bilayers deposited at 300 or 550 °C increases substantially after the RTA treatment at 650 °C, leading to appreciable increase in the total stress of the whole Ti/TiN/W stack. The nucleation deposition of W on the annealed Ti/TiN is somewhat hindered. The retardation of W growth on annealed Ti/TiN is discussed in terms of thermodynamics and classical nucleation theory in conjunction with the reduction of the interfacial impurities (i.e. fluorine and oxygen) as a result of the RTA of Ti/TiN [ A. Mouroux, R. Palmans, J. Keinonen, S.-L. Zhang, K. Maex, S. Petersson, in: Materials Research Society, MRS, San Francisco, CA, 1996 ], as well as the evolution of the W film texture with the W thickness.

Interfacial vibrational modes ~IFM’s! of CdSe/ZnTe superlattice are shown for perfect and atomically rearranged interfaces with four probable exchange configurations. In addition to the IFM at 222 cm originating from single interface Zn-Se ‘‘wrong’’ bonds ~WB’s!, another IFM at 235 cm occurs due to atomic rearrangement at the interfaces, which is attributed to double Zn-Se WB’s. Raman scattering on both atomiclayer-epitaxy and molecular-beam-epitaxy grown samples is reported. Using the experimental data for the 218 cm line of LIF as a base for improving calculations, the corresponding LIF2 line is predicted at 228 cm. Experiments failed to detect this line owing to insufficient double WB’s with long-range order. This characteristic IFM is observed in an annealed sample, with abnormally strong intensity at 227 cm. @S0163-1829~98!01903-1#

A mathematical model of oxidation of SixGe1−x alloys is presented. The growth of SiO2 is simulated in conjunction with the determination of silicon distribution in SixGe1−x using numerical methods. The main feature of the model is the assumption of simultaneous oxidation of germanium and silicon when exposing the SixGe1−x to an oxidizing atmosphere. In accordance with thermodynamics, the GeO2 formed is subsequently reduced by the (free) silicon available at the interface between the growing SiO2 and the remaining SixGe1−x through a reduction reaction. Thus, the enhanced oxidation of silicon in the presence of germanium is modeled as a result of the rapid oxidation of germanium followed by the quick reduction of GeO2 by silicon. The growth of a mixed oxide in the form of either (Si,Ge)O2 or SiO2–GeO2 only occurs when the supply of silicon to the SiO2/SixGe1−x interface is insufficient. A comparison is made between simulation and experiment for wet oxidation (in pyrogenic steam) of polycrystalline SixGe1−x ...

The oxidation of polycrystalline SixGe1−x films with different compositions (i.e., different values of x) is carried out in pyrogenic steam at 800 °C for various lengths of time. It is found that the oxidation is enhanced by the presence of germanium and that the enhancement effect is more pronounced for the films richer in germanium. A mixed oxide in the form of either (Si,Ge)O2 or SiO2–GeO2 is found at the sample surface if the initial SixGe1−x contains more than 50% of germanium. However, a surface silicon cap layer of about 14 nm is found to have a significant impact on the oxidation of the Si0.5Ge0.5 films; it leads to the growth of about 115-nm-thick SiO2 which is about four times that of the SiO2 resulting from the oxidation of the cap layer itself. On the SixGe1−x films with only 30% of germanium, the SiO2 continues to grow after oxidation for 180 min resulting in 233-nm-thick SiO2 which is about 2.4 times greater than the SiO2 grown on 〈100〉 silicon substrates. Rejection of germanium results in p...

In this work, the formation of TiSi/sub 2/ from Ti/Mo bilayers on both blanket and patterned poly-Si substrates during rapid thermal annealing (RTA) was first studied by means of electrical measurements on van der Pauw test structures. Then, ohmic contacts between the silicide and both p- and n-type Si, as well as electrical shorts between the gate and source/drain electrodes were investigated.

The breakdown of self-incompatibility, which could result from the accumulation of non-functional S-haplotypes or competitive interaction between two different functional S-haplotypes, has been studied extensively at the molecular level in tetraploid Rosaceae species. In this study, two tetraploid Chinese cherry (Prunus pseudocerasus) cultivars and one diploid sweet cherry (Prunus avium) cultivar were used to investigate the ploidy of pollen grains and inheritance of pollen-S alleles. Genetic analysis of the S-genotypes of two intercross-pollinated progenies showed that the pollen grains derived from Chinese cherry cultivars were hetero-diploid, and that the two S-haplotypes were made up of every combination of two of the four possible S-haplotypes. Moreover, the distributions of single S-haplotypes expressed in self- and intercross-pollinated progenies were in disequilibrium. The number of individuals of the two different S-haplotypes was unequal in two self-pollinated and two intercross-pollinated progenies. Notably, the number of individuals containing two different S-haplotypes (S1- and S5-, S5- and S8-, S1- and S4-haplotype) was larger than that of other individuals in the two self-pollinated progenies, indicating that some of these hetero-diploid pollen grains may have the capability to inactivate stylar S-RNase inside the pollen tube and grow better into the ovaries.

The redistribution of titanium during the formation of epitaxial CoSi2, grown from the reaction of Co(20 nm)/Ti(10 nm) bilayers with Si 〈100〉, has been investigated. Annealing of Co/Ti/Si structures, at temperatures between 850 and 1050 °C, is shown to be associated with the growth of an inhomogeneous CoSi2 layer having Ti‐rich surface layer(s) on top. The formation of inhomogeneities in the CoSi2 layer is conclusively attributed to the presence of Ti‐rich surface layer(s). It is shown that smooth and morphologically stable CoSi2 layers can be grown by removing these surface layers followed by a high‐temperature treatment in nitrogen atmosphere. We propose that the underlying mechanism for the inhomogeneity formation within the CoSi2 layer is a nucleation‐controlled process, induced by an anticipated reaction between the CoSi2 layer and Ti‐rich phases near the surface.

Because of the current interest in using in-situ resistance measurements for the rapid investigation of thin film reactions and transformations, it is important to understand the various morphologies that the resistance versus temperature curves may assume. Several typical conditions for both planar reactions (as in silicide formation) and lateral transformations (as in the crystallization of amorphous films) have been explored. The characteristic features of the curves, e.g. inflection points, are analyzed for different conditions such as an increase or decreased in resistance. Emphasis is placed on understanding the appearance, or absence of such features, and on their relation to fundamental reaction characteristics such as heat generation.

Some silicides and other intermetallic compounds can form protective layers of SiO2, Al2O3, etc., when exposed to oxidizing atmospheres at high temperatures. As a result they are interesting for use in structural parts subjected to such conditions, for example in aerospace technology. The present article is an attempt at modelling the thermodynamic and kinetic conditions that allow such protective layers to form. At the same time, one defines the limits (in fact low temperatures) beyond which the growth of such protective layers becomes impossible, often causing the onset of catastrophic failure referred to as the pest phenomenon. The thermodynamic parameters necessary for a quantitative evaluation of the oxidation process are relatively well known. That is not true of the kinetic factors which in the respective compounds have been determined but vaguely. Thus it is difficult to arrive at a true quantitative formulation of the results. Qualitatively, the situation is more satisfactory. For exampl...

Compressively strained Si/sub 0.7/Ge/sub 0.3/ surface-channel pMOSFETs with atomic layer deposition (ALD) Al/sub 2/O/sub 3//HfO/sub 2//Al/sub 2/O/sub 3/ nanolaminate and low-pressure chemical vapor deposition p/sup +/ poly-SiGe gate electrode were fabricated. Surface treatment with either hydrogen fluoride (HF) clean, or HF clean followed by water rinse was performed prior to the ALD processing. The devices with water rinse show a good control of interfacial layer and device reproducibility, while the devices without water rinse lack a clearly observable interfacial layer and show scattered electrical characteristics and distorted mobility curve. A /spl sim/20% increase in hole mobility compared to the Si universal mobility and a /spl sim/0.6-nm-thick continuous interfacial layer are obtained for the pMOSFETs with water rinse.

Tungsten (W) films are deposited from tungsten hexafluoride on sputter‐deposited TiN adhesion layers in a cold‐wall chemical vapor deposition reactor. The film resistivity of the W films is found to be thickness dependent. It decreases monotonically with increasing film thickness. Typical resistivity values of 40‐nm‐thick W films are about 19.3–23.4 μΩ cm, depending on the structure of the underlying TiN layer used. The resistivity of a 980‐nm‐thick W film is 9.8 μΩ cm. Oxygen and fluorine impurities, as well as structural difference in the W films are found to be the major causes for the resistivity variations. Lowering impurity level and/or increasing W crystallite size can decrease film resistivity. The stress of all the W films is found to be tensile, independent of the structure of the TiN layers. However, the absolute value of the stress is intimately associated with the structure of the TiN layers. The stress values can differ by a factor of more than 2 for the 40‐nm‐thick W films deposited on the ...

Based on the calculation of lattice dynamic properties and observation of first-order Raman spectra for the Zn-Se localized microscopic interface mode of the (CdSe${)}_{4}$/(ZnTe${)}_{4}$ superlattice, multiphonon (MP) Raman scattering of up to five orders has been observed. The linewidth variation with MP order and temperature as well as the frequency and intensity behavior with MP order can be interpreted by the anharmonic decay of the localized mode into extended band modes. These results show the defectlike nature of interfaces in AB/CD-type superlattices.