Oxidation of tungsten single crystals in the presence of a high-electric field

The effects of high-electric fields on oxidation of tungsten single crystals in 6 × 10^?4 torr of oxygen at 1200–1500 °K were studied by field emission and transmission electron microscopy. Exposure of field emitters to oxygen in the absence of a field resulted in the build-up of emitter tips. Oxidation under the application of a negative or positive field, on the other hand, involved plane faceting and formation of oxide crystallites. Plane faceting was recognized to occur on the {111} and the {112} regions, showing the facetings of the {111} and the {112} planes into the {110} planes, whereas, crystallite formation seemed to take place selectively on the {100} regions. It was suggested by field emission microscopy that negative fields have an additional effect which causes the growth of an oxide crystal on the (110) plane. Transmission electron microscopy of an emitter oxidized in a negative field actually revealed a tiny oxide crystal with a size of ～ 300 Å grown on the developed (110) plane. The crystal exhibited a triangular shadow image strongly indicating an external pyramid-like form.     

Growth and desorption of indium epitaxial layers investigated by high field microscopy

Growth of indium single crystals on tungsten field emission tips was carried out by deposition of indium from vapour in ultra high vacuum, using substrate temperatures in the range of 293–420 K. Two different tungsten tips were used as the substrate: a perfect W single crystal in one case and a bi-crystal with a distinct grain boundary in the other. No influence of the grain boundary on the epitaxial growth was found. Two orientation relationships were observed mostly: {111}In ∥ {110}W with 〈110〉In ∥ 〈111〉W and {111}In ∥ {100}W with 〈110〉In ∥ 〈110〉W. In the first case the growth was initiated by the indium nucleus created on the ledges of the {110}W plane. A field strength of 0.9 V/Å was found for the evaporation field of indium. The field strength of the desorption of In-W interfacial layer atoms was found to be 4.4–5.2 V/Å. A mechanism of the growth of indium crystals has been proposed.     

The bordoni peak in silver single crystals at megahertz frequencies

Summary The dislocation relaxation maximum has been investigated at frequencies of 5, 10 and 30 MHz. The three (very high-purity) silver crystals of crystallographic orientation 〈111〉, 〈110〉 and 〈100〉 which are given a resolved shear stress of 20 MPa were found to produce dislocation relaxation maximum at 107 K in all the three samples. The maximum shifts to 117 K when measurement is carried out at 10 MHz and to 127 K at 30 MHz. The results reveal that the maximum is orientation independent. The activation energy and the attempt frequency were calculated and found to be equal to 0.105 eV and 2·10⁹ Hz, respectively. Meanwhile the larger magnitude of the maximum was found on the 〈111〉 crystal and the least was on the 〈100〉 crystal. Finally, it was clearly shown that the dislocation relaxation strength decreases as the frequency increases.     

Orientation dependence of electrical properties of 0.96Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>-0.04BaTiO<Subscript>3</Subscript> lead-free piezoelectric single crystal

In this paper, a single crystal of 0.96Na_0.5Bi_0.5TiO₃-0.04BaTiO₃ with dimensions of Φ 30×10 mm was grown by the top-seeded-solution growth method. X-ray powder diffraction results show that the as-grown crystal possesses the rhombohedral perovskite-type structure. The dielectric, piezoelectric and electrical conductivity properties were systematically investigated with 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples. The room-temperature dielectric constants for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples are found to be 650, 740 and 400 at 1 kHz. The (T _m, ε _m) values of the dielectric temperature spectra are almost independent of the crystal orientations; they are (306°C, 3718), (305°C, 3613) and (307°C, 3600) at 1 kHz for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal. The optimum poling conditions were obtained by investigating the piezoelectric constants d ₃₃ as a function of poling temperature and poling electric field. For the 〈001〉 and 〈110〉 crystal samples, the maximum d ₃₃ values of 146 and 117 pC/N are obtained when a poling electric field of 3.5 kV/mm and a poling temperature of 80°C were applied during the poling process. The as-grown 0.96Na_0.5Bi_0.5TiO₃-0.04BaTiO₃ crystal possesses a relatively large dc electrical conductivity, especially at higher temperature, having a value of 1.98×10⁻¹¹ Ω⁻¹⋅m⁻¹ and 3.95×10⁻⁹ Ω⁻¹⋅m⁻¹ at 25°C and 150°C for the 〈001〉 oriented crystal sample.     

Diamond cleavage: importance to high pressure research

The extraordinary properties of diamond make it the number-one choice for anvils in high pressure experiments involving anvil cells. In much of the literature on the properties of diamond the only cleavage mentioned is {111}. However, experience has shown that diamond anvils made with their [001] axis oriented in line with the principal stress axis of the anvil or at a small angle to it often failed with flat faces having {110} orientations; a cleavage plane is reported in some publications. Analysis of the anisotropy of strength and Poisson ratio in diamond has shown that such orientations do, indeed, favor initial failure on {110} cleavage planes. This analysis, in conjunction with stereographic projections of the {111} and {110} cleavage planes, suggests that a 27° tilt of the [001] axis with respect to the linear stress axis by rotation around the [100] or [010] axis should provide significantly greater resistance to failure by cleaving.     

Special misorientations in localized deformation regions in Fe-3%Si alloy single crystals

Extended regions located at an angle of 20° to the rolling plane are observed inside deformation bands in a (110)[001] Fe-3%Si alloy single crystal at a high strain (～60%). These regions were interpreted earlier as shear bands. The lattice orientation in these bands is close to (110)[001], and their habit plane is parallel to the {112} planes of the deformed {111}〈112〉 matrix. The misorientations between the bands and the matrix group around special misorientations Σ9, Σ19a, Σ27a, and Σ33a, which are characterized by close angles of rotation about axis 〈110〉. During primary recrystallization, the (110)[001] grains growing from the bands retain segments of the corresponding special boundaries with the deformed matrix.     

Ultrasonic investigations in intermetallics

Ultrasonic attenuation for the longitudinal and shear waves due to phonon-phonon interaction and thermoelastic mechanism have been evaluated in B2 structured intermetallic compounds AgMg, CuZr, AuMg, AuTi, AuMn, AuZn and AuCd along 〈100〉, 〈111〉 and 〈110〉 crystallographic directions at room temperature. For the same evaluations, second- and third-order elastic constants, ultrasonic velocities, Grüneisen parameters, non-linearity parameter, Debye temperature and thermal relaxation time are also computed. Although the molecular weight of these materials increases from AgMg to AuCd, the obtained results are affected with the deviation number. Attenuation of ultrasonic waves due to phonon-phonon interaction is predominant over thermoelastic loss. Results are compared with available theoretical and experimental results. The results with other well-known physical properties are useful for industrial purposes.      

Orientation of chemisorbed species from orthogonal-plane arups: Tilted CO on Pt{110} and upright CO on Pt{111}.

Angle-resolved photoemission spectra obtained with electron collection in the plane orthogonal to the incidence plane, using a He II photon source, are used to provide an accurate measure of the orientation of chemisorbed diatomic molecules. As previously established, CO in the Pt{111}c(4 × 2) structure is found to be chemisorbed in an upright configuration, whereas in the Pt{110}(2 × 1) p1g1 structure the CO molecular axis is tilted 26 ± 2° away from the surface normal, in a direction between [211] and [433].     

Structure and composition of tungsten silicide thermal-field microprotrusions

The thermal-field microprotrusions that grow on the surface of a tungsten tip coated with silicon when the tip is heated in an electric field are investigated by a suite of field emission methods, including electron field emission, ion desorption microscopy, and the atomic-probe method. For Si coatings more than a few monolayers thick, microprotrusions are observed to grow in the field desorption regime when the tip is heated to temperatures T=1100–1200 K in an electric field with initial intensity F=5.7–8.6×10⁷ V/cm. The field at which they evaporate is 1.2–1.8×10⁸ V/cm. The set of moving spots (i.e., microprotrusions) forms rings whose collapse signals the dissolution of the thermal-field growths on the developed faces. The most interesting structures are the sharp microprotrusions that grow on the central facet of a {110} tungsten tip under certain conditions. Atomic-probe analysis of their composition reveals that they consist of tungsten trisilicide WSi₃ with a monolayer surface skin whose composition is close to WSi₂. The intense growth of these formations on an initially smooth closepacked {110} face of tungsten is evidence that reconstruction of the latter takes place under the influence of the strong field and the interaction with silicon. Zh. Tekh. Fiz. 67, 102–109 (September 1997)     

Study on titanium carbide field emitters by field-ion microscopy,field-electron emission microscopy,Auger electron spectroscopy,and atom-probe field-ion microscopy

Surface structure, composition, and some field-electron emission properties are examined for thermally annealed titanium carbide emitters. As a result of high temperature heating, low-index planes of {100} and {111} become facetted and are observed as dark areas in field-electron emission patterns. Electrons are emitted predominantly from the {110} planes. The surface composition becomes enriched with carbon when the carbon deficient titanium carbide, TiC_0.71, is heated at high temperatures in vacuum better than 10^?7 Pa. The topmost (110) layer consists of both Ti and C atoms. The instability in the electron emission current of titanium carbide is considered to be due to the local work function change caused by an interaction between vacuum residual gases and chemically active titanium atoms on the emitter surface.     

Deformation and annealing textures of rolled nickel single crystals

Textural and structural analysis is conducted on nickel single crystals of unstable orientation in a compression deformed (=83%) and annealed state. The formation of different deformation textures (DT) on opposite surfaces of compressed crystals is established. The relief and band structure corresponds to two-component DT {110} 112, observed in the compression plane. Annealing (573°K) leads to the appearance of recrystallization grains on the two component DT side {110} 112. Orientationally, the first recrystallization grains correspond to the intersection of the peripheral portions of the texture maxima associated with both components of DT. On the side with DT {123} 212, indications of recrystallization were not observed. Application of the texture method with defocus allowed the comparison of the state of the lattice in the regions of the crystal having different orientations. The experimentally observed inhomogeneity of the development of the structure for primary recrystallization is explained by the inhomogeneity of the deformed structure and by orientational factors.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 45–50, June, 1986.     

Adsorption of doping elements at antiphase boundaries in ordered ternary alloys

A discussion is presented of the theory for the adsorption of doping elements at 1/2 111 {110} antiphase boundaries in ordered ternary alloys with bcc lattices. It is shown that there may may be a significant segregation of the doping elements at the antiphase boundaries; conditions for the formation of segregations at antiphase boundaries in ternary alloys are obtained and analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 3, pp. 32–42, March, 1969.     

Epitaxial growth defects and interfacial structures of Cu deposited on TiO2

Epitaxial growth defects and the interfacial structure between vapor deposited Cu and TiO₂(110) have been studied by combined high-resolution electron microscopy (HREM) and image simulations. The Cu film was found to grow epitaxially with an orientation given by Cu(111)//TiO₂(110) and Cu110//TiO₂ [001]. With this relationship, there exist two equivalent domain orientations which are rotated with respect to each other by 180°. Localized misfit dislocations have not been detected, but {111} stacking faults and microtwins were observed which may occur as a result of 3-D island coalescence. HREM observations and image simulations have been used to study the interface atomic structure. The dominant interfacial structure has a stoichiometric (110) TiO₂ surface with bridging rows of O atoms and occasionally, an interfacial structure having a reduced (110) TiO₂ surface terminated by both Ti and O atoms has been observed locally.     

Electron states and atomic positions at the {001}, {110} and {111} faces of W and Mo

The results of ab initio calculations on the {001}, {110} and {111} surfaces of W and Mo and on the (√2 × √2)R45° reconstructed W {001} surface are presented. A distribution of surface states in reasonable agreement with experiment is found. A simple parametrisation of the short range repulsive force between transition metal atoms is used to predict, for all these surfaces, relaxations which are comparable with those observed. This same parametrisation indicates that the W and Mo {001} surfaces are stable to proposed reconstructive displacements.     

Electron Backscattered Diffraction of Transgranular Crack Propagation in Soft Steel

We consider the crack propagation in a soft steel sheet during the formation. The drawability is considered in relation with the structural anisotropy, the mechanical behaviour is related to both the grain morphology and the texture. The structure heterogeneity could lead to the apparition of micro-cracks. The results show the texture effect on the crack propagation and on the crack arrest in soft steel during the formation. The EBSD technique allows to show that the adjustment of the grain orientation from the initial main component {111}（112） towards the deformation orientation {111}（110） incites a trans-granular crack through a grain with initial {111}（112） orientation in a globally ductile material. It is the presence of grains with {111}（110） orientation which permits the closing of micro-cracks.     

Thermal oxidation effect on structural and optical properties of?heavily doped phosphorus polycrystalline silicon films

The study reported in this paper contributes to better understanding the thermal oxidation effect on structural and optical properties of polycrystalline silicon heavily in situ P-LPCVD films. The deposits, doped at levels 3×10¹⁹ and 1.6×10²⁰ cm⁻³, have been elaborated from silane decomposition (400 mTorrs, 605°C) on monosilicon substrate oriented 〈111〉. The thermal oxidation was performed at temperatures: 850°C during 1 hour, 1000, 1050, and 1100°C during 15 minutes. The XRD spectra analysis pointed out significant 〈111〉 texture evolution, while in the case of 〈220〉 and 〈311〉 textures, the intensities are practically invariant (variations fall in the uncertainty intervals). The optical characterizations showed that refractive index and absorption coefficient are very sensitive to the oxidation treatment, mainly when the doping level is not very high. We think that atomic oxygen acts as defects passivating agent leading to carriers’ concentration increasing. Besides, the optical behavior is modeled in visible and near infrared, by a seven-term polynomial function n ²=f(λ ²), with alternate signs, instead of theoretically unlimited terms number from Drude’s model. It has been shown that fitting parameters fall on Gaussian curves like they do in the theoretical model.     

Polarization manipulated solid-state lasers with crystalline-orientations

The polarization states of 〈111〉-cut Yb:YAG crystal microchip lasers were investigated by pumped with the elliptically polarized pump beam from fiber-coupled laser-diode. The manipulated polarized lasers were achieved in laser-diode pumped Yb:YAG microchip laser by controlling the crystalline-orientations in 〈111〉-growth Yb:YAG crystal. Generally elliptically polarized lasers were obtained in laser-diode pumped Yb:YAG microchip lasers. However, crystalline-orientation manipulated linearly polarized laser was obtained when six different sites with different crystalline orientations were set to parallel to the major axis direction of the elliptically polarized pump beam. Six different sites in Yb:YAG crystal were separated with 30° and 90°, which were responsible for the linearly polarized laser oscillations. Circularly polarized lasers were observed when a Yb:YAG crystal was aligned to a special position between two sites responsible for linearly polarized laser oscillation. Effects of the polarization states of pump source on the laser polarization states of Yb:YAG microchip lasers and polarization direction of different polarized lasers with respect to Yb:YAG crystal rotation was addressed.     

Acoustic wave propagation in barium monochalcogenides in the B1 phase

Temperature dependence of ultrasonic attenuation due to phonon-phonon interaction and thermoelastic loss have been studied in (NaCl-type) barium monochalcogenides [BaX, X = S, Se, Te], in the temperature range 50–500 K; for longitudinal and shear modes of propagation along 〈100〉, 〈110〉, 〈111〉 directions. Second and third order elastic constants have been evaluated using electrostatic and Born repulsive potentials and taking interactions up to next nearest neighbours. Gruneisen parameters, nonlinearity constants, nonlinearity constants ratios and viscous drag due to screw and edge dislocations have also been evaluated for longitudinal and shear waves at 300 K. In the present investigation, it has been found that phonon-phonon interaction is the dominant cause for ultrasonic attenuation. The possible implications of results have been discussed. The text was submitted by the authors in English.     

The lattice deformation and the energy of antiphase boundaries in Fe-Si alloys

The lattice deformation across the antiphase boundary and the energy of both types (a/2111 anda(100) of antiphase boundaries lying in {110} plane are calculated using a series of three interatomic potentials fitted to experimental data. It is shown that the relaxation of atomic planes in the vicinity of antiphase boundary is important for thea/2111 antiphase boundary and is negligible for a 100 antiphase boundary in the DO₃ structure.The author is grateful to Dr. F.Kroupa and to Dr. A.Gemperle for valuable discussions.     

Self-assembled magnetic nanostructures: Epitaxial Ni nanodots on TiN/Si (001) surface

Systems containing single domain magnetic particles are of great interest in view of their possible applications in ultrahigh-density data storage and magnetoelectronic devices. The focus of this work is plan-view STEM Z-contrast imaging study of the self-assembly growth of magnetic nickel nanostructures by domain matching epitaxy under Volmer–Weber (V–W) mode. The growth was carried out using pulsed laser deposition (PLD) technique with epitaxial titanium nitride film as the template, which was in turn grown on silicon (001) substrate via domain matching epitaxy. Our results show that the base of nickel islands is rectangular with the two principal edges parallel to two orthogonal 〈110〉 directions, which is [110] and [] for [001] oriented growth. The size distribution of the islands is relatively narrow, comparable to that obtained from self-assembled islands grown under Stranski–Krastanow (S–K) mode. A certain degree of self-organization was also found in the lateral distribution of islands: island chains were observed along the directions close to 〈011〉, which are also the edge directions. The interaction between neighboring islands through the island edge-induced strain field is believed to be responsible for the size uniformity and the lateral ordering.An erratum to this article can be found at