共查询到20条相似文献,搜索用时 15 毫秒
1.
By using the highly precise all-election full potential linearized augmented plane-wave method based on density functional theory within the generalized gradient approximation, we investigated magnetocrystalline anisotropy and magnetism of zinc-blende CrTe (001) surface. We observed that both of the Cr- and Te-terminated zinc-blende CrTe (001) surfaces maintain the half-metallicity by analyzing the density of states. The magnitudes of the calculated magnetic moments for the Cr(S) and Cr(S-1) atoms are calculated to be 3.92 and 3.16 μB for the Cr- and Te-terminated surfaces, respectively. The Te atoms show significantly induced negative spin polarizations of 0.13-0.30 μB. The spin orientations at the Te-terminated (Cr-terminated) surfaces were found to be in-plane (out-of-plane) regardless of its thickness. Since a Te-terminated surface is known as to be more stable than a Cr-terminated one, our result is consistent with an experiment which observed in-plane magnetic anisotropy at a CrTe (001) surface. 相似文献
2.
Summary Microindentation experiments have recently shown that silicon can exhibit plastic flow when subjected to high pressure. Assuming that under these conditions the relevant reference structure is the -Sn high-pressure phase of silicon, we apply the magic-strain concept to explore the space of configurations that could describe the observed behavior. We use first-principles total-energy calculations (including full relaxation of the atomic basis for every structure) to evaluate the relevance of strained configurations. Using this approach, we were able to identify a low-energy path that corresponds to planar flow of the atoms. The atomic configurations along this path provide insight into possible microscopic motions under high pressure that may be relevant to plastic flow in silicon. 相似文献
3.
The heterogeneous nucleation theory of silicon on SiO2 and Si3N4 substrates has been developed using classical theory. It is shown that the experimental observations can be explained on
the basis of the bond energies of O-H, N-H and Si-H. A reaction model is proposed for the growth of silicon on silicon from
silane, using hydrogen as a carrier gas in the temperature region 600–900°C. The growth rate of silicon is shown to be equal
toP
SiH
4
P
H
2 when the partial pressure of hydrogen is high, and is independent of the total pressure and the partial pressure of hydrogen
in the lower region. 相似文献
4.
Recent experiments suggest that self-assembled Bi nanolines on the passivated Si(0 0 1) surface can be used as templates to grow one-dimensional arrays of noble-metal (Au, Ag) nanoclusters. In order to ascertain this template effect, the gold atom on the H-terminated Si(0 0 1) surface and that on the Bi line are examined by density-functional methods. The calculation indicates that the gold atom enters a Si dimer on the H-terminated surface and the BiSi backbonds of a Bi dimer on the Bi line. The gold atom is 0.6 eV more stable on the Bi line than on the H-terminated surface. This result suggests the preferential adsorption of gold on the Bi line and confirms its template effect. 相似文献
5.
Jianrong Sun Zhiguang Wang Yuyu Wang Yabin Zhu Kongfang Wei Tielong Shen Fashen Li 《Vacuum》2011,86(4):461
Polycrystalline half-metallic Fe3O4 films with 1 μm in thickness were synthesized on glass substrates directly by electroless plating in aqueous solution at 90 °C without heat treatment. The films have single pure spinal phase structure and the well-crystallized columnar grains grow perpendicularly to the substrates, as revealed by XRD, XPS and SEM. At room temperature, the films exhibit negative magnetoresistance (MR) ratio of about −5.1%, which is ascribed to intergranular tunneling of spin polarized electrons of Fe3O4. The resistivity R of the films with 1 μm in thickness at room temperature is about 5.2 × 10−1 Ω cm. The cation distribution and the arrangement of the magnetic moments of the plated Fe3O4 ferrite thin films are different from that of the bulk materials, which is likely to be one of the reasons for the modification of R and MR properties. 相似文献
6.
AbstractR2Fe3Si5 (R= Sc, Y, Lu) contains nonmagnetic iron and has a relatively high superconducting transition temperature Tc among iron-containing superconductors. An anomalous temperature dependence of specific heat C(T) has been reported for polycrystalline samples down to 1 K. We have grown R2Fe3Si5 single crystals, confirmed the anomalous C(T) dependence, and found a second drop in specific heat below 1 K. In Lu2Fe3Si5, we can reproduce C(T) below Tc, assuming two distinct energy gaps 2Δ 1/kBTc = 4.4 and 2Δ 2/kBTc = 1.1, with nearly equal weights, indicating that Lu2Fe3Si5 is a two-gap superconductor similar to MgB2. Hall coefficient measurements and band structure calculation also support the multiband contributions to the normal-state properties. The specific heat in the Sc2Fe3Si5 single crystals also shows the two-gap feature. R5Ir4Si10 (R = Sc, rare earth) is also a superconductor where competition between superconductivity and the charge-density wave is known for rare earths but not for Sc. We have performed detailed specific heat measurements on Sc5Ir4Si10 single crystals and found that C(T) deviates slightly from the behavior expected for weak-coupling superconductors. C(T) for these superconductors can also be reproduced well by assuming two superconducting gaps. 相似文献
7.
Tsuyoshi Tamegai Yasuyuki Nakajima Tsuyoshi Nakagawa Guoji Li Hisatomo Harima 《Science and Technology of Advanced Materials》2008,9(4)
R2Fe3Si5 (R= Sc, Y, Lu) contains nonmagnetic iron and has a relatively high superconducting transition temperature Tc among iron-containing superconductors. An anomalous temperature dependence of specific heat C(T) has been reported for polycrystalline samples down to 1 K. We have grown R2Fe3Si5 single crystals, confirmed the anomalous C(T) dependence, and found a second drop in specific heat below 1 K. In Lu2Fe3Si5, we can reproduce C(T) below Tc, assuming two distinct energy gaps 2Δ 1/kBTc = 4.4 and 2Δ 2/kBTc = 1.1, with nearly equal weights, indicating that Lu2Fe3Si5 is a two-gap superconductor similar to MgB2. Hall coefficient measurements and band structure calculation also support the multiband contributions to the normal-state properties. The specific heat in the Sc2Fe3Si5 single crystals also shows the two-gap feature. R5Ir4Si10 (R = Sc, rare earth) is also a superconductor where competition between superconductivity and the charge-density wave is known for rare earths but not for Sc. We have performed detailed specific heat measurements on Sc5Ir4Si10 single crystals and found that C(T) deviates slightly from the behavior expected for weak-coupling superconductors. C(T) for these superconductors can also be reproduced well by assuming two superconducting gaps. 相似文献
8.
A. Furlan G.K. Gueorguiev H. Högberg S. Stafström L. Hultman 《Thin solid films》2006,515(3):1028-1032
Inherently nanostructured CPx compounds were studied by first-principles calculations. Geometry optimizations and cohesive energy comparisons show stability for C3P, C2P, C3P2, CP, and P4 (P2) species in isolated form as well as incorporated in graphene layers. The energy cost for structural defects, arising from the substitution of C for P and intercalation of P atoms in graphene, was also evaluated. We find a larger curvature of the graphene sheets and a higher density of cross-linkage sites in comparison to fullerene-like (FL) CNx, which is explained by differences in the bonding between P and N. Thus, the computational results extend the scope of fullerene-like thin film materials with FL-CPx and provide insights for its structural properties. 相似文献
9.
A. Ali-MessaoudA. Chikouche A. Estève A. Hemeryck C. Lanthony C. Mastail M. Djafari Rouhani 《Thin solid films》2012,520(14):4734-4740
We present a synthetic review of elementary chemical mechanisms source of the oxidation of pure silicon (100) surfaces. These mechanisms are then discussed from their ability to build a mesoscale model of the Kinetic Monte Carlo type dedicated to the process simulation of silicon thermal oxidation. We show that oxidation is driven by two main processes: (i) charge transfer arising from the formation of SiO bonds in contact to pure silicon at the interface, (ii) destructive oxidation in which SiO building blocks rearrange at the interface to form a hexagonal-based oxide network directly in contact to cubic Si layers. Based on these considerations, simulations at the process scale exhibit epitaxial behavior within the interfacial domain. The resulting oxide layers are analyzed in terms of local to more extended defects. We observe two types of defects: (i) “intra-domain defects” which are related to local distortion of the elementary hexagonal oxide pattern Si6O6 (ii) “inter-domain defects”, which are related to global oxide structural transitions from one orientation to another. 相似文献
10.
Bharat Bajaj 《Thin solid films》2010,519(3):1219-1223
Amine modified iron oxide (Fe3O4) nanoparticles were synthesized by thermal decomposition method and were further used to bio-functionalize by grafting of N-hydroxysuccinimide (NHS) ester of folate and ethylenediaminetetraacetate (EDTA). Fe3O4 nanoparticles of ~ 22 nm were confirmed from X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. FT-IR studies indicated two bands at 1515 cm− 1and 1646 cm− 1, which can be attributed to carboxylic group and the amide linkage respectively, revealing the conjugation of folate with Fe3O4. The conjugation of the chelating agent showed strong C=O stretch and Fe-O vibrations at 1647 and 588 cm− 1 respectively. The value of saturation magnetization for Fe3O4 nanoparticles was found to be 88 emu/g, which further reduced to 18 and 32% upon functionalization with EDTA and NHS ester folate, respectively. These amine modified Fe3O4 nanoparticles can also be functionalized with other bifunctional chelators, such as amino acids based diethylene triamine pentaacetic acid (DTPA), and thus find potential applications in radio-labeling, biosensors and cancer detection, etc. 相似文献
11.
The nitridation behavior of silicon powder with added Zr compounds was studied in order to assess the catalytic effect of zirconium on the formation of reaction bonded silicon nitride, using high purity silicon powder and monoclinic zirconia as starting materials. Thermogravimetric analysis revealed that the addition of ZrO2 to Si powder reduced the temperature of the main nitridation reaction, and increased the amount of silicon converted to silicon nitride at a given temperature. On the other hand, the nitridation rate at higher temperatures (1380-1400 °C) indicated similar values for both pure Si and Si with ZrO2 additions. 相似文献
12.
Transient absorption in 394-435 nm wavelength range following 193 nm photolysis of disilane has been measured by using cavity ring-down spectroscopy (CRDS). A broad and continuum absorption band was observed. Time profiles of the absorption measured at several wavelengths were similar and found to have at least two components. The decaying part of the absorption can be attributed to Si(H2)Si based on the kinetic consideration and available information from the literature. The absorption was also measured in the hot wire CVD (HW-CVD) of SiH4. A broad and continuum band was observed. 相似文献
13.
C/Fe3O4 hybrid materials have potential applications in sensors and anode materials for lithium-ion batteries. In this text, a one-step pyrolysis method was used to prepare C/Fe3O4 hybrid materials from EDTA ferric sodium salt. The magnetic Fe3O4 nanoparticles can be homogeneously incorporated into carbon materials to form C/Fe3O4 hybrids during the reaction. The morphology and magnetism of the C/Fe3O4 hybrids are strongly affected by pyrolysis temperature. This method supplies an ideal template to facilely synthesize C/metal-oxide hybrid materials from EDTA metallic salts. 相似文献
14.
Oliver Skibitzki Yuji YamamotoMarkus Andreas Schubert Bernd Tillack 《Thin solid films》2012,520(8):3271-3275
The solid phase epitaxy (SPE) of undoped amorphous Si (a-Si) deposited on SiO2 patterned Si(001) wafers by reduced pressure chemical vapor deposition (RPCVD) using a H2-Si2H6 gas system was investigated. The SPE was performed by applying in-situ postannealing directly after deposition process. By transmission electron microscopy (TEM) and scanning electron microscopy, we studied the lateral SPE (L-SPE) length on sidewall and mask for various postannealing times, temperatures and a-Si thicknesses. We observed an increase in L-SPE growth for longer postannealing times, temperatures and larger Si thicknesses on mask. TEM defect studies revealed that by SPE crystallized epi-Si exhibits a higher defect density on the mask than at the inside of the mask window. By introducing SiO2-cap on the sample with 180 nm Si thickness following postannealing at 570 °C for 5 h, the crystallization of up to 450 nm epi-Si from a-Si is achieved. We demonstrated the possibility to use this technique for SiGe:C heterojunction bipolar transistor (HBT) base layer stack to crystallize Si-buffer layer to widen the monocrystalline region around the bipolar window and to improve base link resistivity of the HBT. 相似文献
15.
The nitriding thermochemical treatment (NTT) is commonly used for steels. In this paper, the experimental conditions required
for NTT, and the influence of such treatments on the structure and hysteresis loops of Co74Fe8B12Si6 and Co74Fe4Mn4B12Si6 ribbons are reported. The results have been compared with those obtained with ribbons treated according to conventional thermal
treatment (CTT) as well. 相似文献
16.
Effect of solid content on pore structure and mechanical properties of porous silicon nitride ceramics produced by freeze casting 总被引:1,自引:0,他引:1
Feng Ye Jingyi ZhangLimeng Liu Haijiao Zhan 《Materials Science and Engineering: A》2011,528(3):1421-1424
Porous Si3N4 ceramics were prepared by freeze casting using liquid N2 as refrigerant. The pore structure, porosity, α → β-Si3N4 transformation and mechanical properties of the obtained materials were strongly affected by the solid contents of the slurries. Increasing the solid content would reduce the porosity, decrease the pore size and change the pore structure from the aligned channels with dendrites to the round pores with decreased pore size. The formation of this round pores impeded the α → β-Si3N4 phase transformation, but was beneficial to the mechanical properties of the obtained porous Si3N4 due to its unique pore structure. 相似文献
17.
Liu Changshi 《Vacuum》2003,72(1):91-95
The interfacial structures of double interfaces system of Si3N4/SiO2/Si were examined using X-ray photoelectron spectroscopy (XPS) before and after 60Co radiation. The experimental results demonstrate that there existed two interfaces, one consisted of Si3N4 and SiO2, while another was made of Si and SiO2, the interface between SiO2 and Si was extended towards the interface of the Si3N4/SiO2 meanwhile the center of the former interface was removed in the direction of the latter interface by 60Co. The concentration of silicon in the Si3N4 state (BE 101.8 eV) was decreased with the variation of radiation dosage as well as bias field within the SiO2-Si interface, remarkably. The mechanism for the experimental results is analyzed. 相似文献
18.
AbstractTextured silicon nitride (Si3N4) has been intensively studied over the past 15 years because of its use for achieving its superthermal and mechanical properties. In this review we present the fundamental aspects of the processing and anisotropic properties of textured Si3N4, with emphasis on the anisotropic and abnormal grain growth of β-Si3N4, texture structure and texture analysis, processing methods and anisotropic properties. On the basis of the texturing mechanisms, the processing methods described in this article have been classified into two types: hot-working (HW) and templated grain growth (TGG). The HW method includes the hot-pressing, hot-forging and sinter-forging techniques, and the TGG method includes the cold-pressing, extrusion, tape-casting and strong magnetic field alignment techniques for β-Si3N4 seed crystals. Each processing technique is thoroughly discussed in terms of theoretical models and experimental data, including the texturing mechanisms and the factors affecting texture development. Also, methods of synthesizing the rodlike β-Si3N4 single crystals are presented. Various anisotropic properties of textured Si3 N4 and their origins are thoroughly described and discussed, such as hardness, elastic modulus, bending strength, fracture toughness, fracture energy, creep behavior, tribological and wear behavior, erosion behavior, contact damage behavior and thermal conductivity. Models are analyzed to determine the thermal anisotropy by considering the intrinsic thermal anisotropy, degree of orientation and various microstructure factors. Textured porous Si3N4 with a unique microstructure composed of oriented elongated β-Si3N4 and anisotropic pores is also described for the first time, with emphasis on its unique mechanical and thermal-mechanical properties. Moreover, as an important related material, textured α-Sialon is also reviewed, because the presence of elongated α-Sialon grains allows the production of textured α-Sialon using the same methods as those used for textured β-Si3N4 and β-Sialon. 相似文献
19.
We deposited silicon nitride films by alternating exposures to Si2Cl6 and NH3 in a cold-wall reactor, and the growth rate and characteristics were studied with varying process temperature and reactant exposures. The physical and electrical properties of the films were also investigated in comparison with other silicon nitride films. The deposition reaction was self-limiting at process temperature of 515 and 557 °C, and the growth rates were 0.24 and 0.28 nm/cycle with Si2Cl6 exposure over 2 × 108 L. These growth rates with Si2Cl6 are higher than that with SiH2Cl2, and are obtained with reactant exposures lower than those of the SiH2Cl2 case. At process temperature of 573 °C where the wafer temperature during Si2Cl6 pulse is 513 °C, the growth rate increased with Si2Cl6 exposure owing to thermal deposition of Si2Cl6. The deposited films are nonstoichiometric SiN, and were easily oxidized by air exposure to contain 7-8 at.% of oxygen in the bulk film. The deposition by using Si2Cl6 exhibited a higher deposition rate with lower reactant exposures as compared with the deposition by using SiH2Cl2, and exhibited good physical and electrical properties that were equivalent or superior to those of the film deposited by using SiH2Cl2. 相似文献
20.
Evolution of surface of sputter-deposited amorphous Si3N4 films growth on Si (100) substrates was investigated using atomic force microscopy (AFM). The scaling behaviors of the AFM topographical profiles were analyzed using the one-dimensional power spectral density. The results of root-mean-square surface height variation showed that there is a power law relationship between the surface roughness and deposition time. It is interesting to note that the growth exponent can be divided into one region and two regions, respectively, when Si3N4 films are deposited at different working pressures. A very low growth exponent of β = 0.07 ± 0.01 was found when Si3N4 films were deposited at a working pressure of 1.6 × 10− 1 Pa. However, the growth exponent β can be divided into two regions, which is β1 = 0.09 ± 0.01, β2 = 0.24 ± 0.03 and β1 = 0.09 ± 0.01, β2 = 0.33 ± 0.04, when the films were deposited at a working pressure of 2.1 × 10− 1 Pa and 2.7 × 10− 1 Pa, respectively. The mechanisms of anomalous dynamic scaling exponents of Si3N4 films deposited at different working pressures were discussed. 相似文献