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1.
应用50%HCl作为浸蚀剂,对助熔法生长的PbFe12O19单晶体的(0001)解理面进行了浸蚀,以显示位错蚀斑。根据蚀斑所具有的形态,将其进行了分类,并确定了各自对应的位错类型。应用Mathews等人提出的机制,解释了在(0001)基面上所观察到的位错蚀斑阵列。
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Based on the beyond-mean-field Skyrme–Hartree–Fock model, impurity effects of the Λhyperon in the hypernuclear systems ${}_{\,{\rm{\Lambda }}}^{25}$ Mg and ${}_{\,{\rm{\Lambda }}}^{29}$ Si are investigated, respectively. Four cases, in which the Λhyperon occupies the single-particle orbitals ${\rm{\Lambda }}$[000]${\tfrac{1}{2}}^{+}$, ${\rm{\Lambda }}$[110]${\tfrac{1}{2}}^{-}$, ${\rm{\Lambda }}$[101]${\tfrac{3}{2}}^{-}$ and ${\rm{\Lambda }}$[101]${\tfrac{1}{2}}^{-}$, are focused. In each case, the potential energy surface and the energy curves projected on certain angular momenta are employed to show the influence of the Λhyperon on the nuclear core. Beside the shrinkage effect that is induced by the Λhyperon occupying the sΛ orbital, it is found that the Λhyperon on the pΛ orbital, ${\rm{\Lambda }}$[110]${\tfrac{1}{2}}^{-}$, drives the nuclear core toward a prolate shape, while the ones on the other two pΛ orbitals, ${\rm{\Lambda }}$[101]${\tfrac{3}{2}}^{-}$ and ${\rm{\Lambda }}$[101]${\tfrac{1}{2}}^{-}$, drive the nuclear core toward an oblate shape. The energy spectra and the corresponding intra-band E2 transition rates for the rotational bands are given as a prediction for future experiments. 相似文献
4.
Electron backscattered diffraction has been used to determine the orientation of WC crystals in a WC-Co composite and atomic force microscopy has been used to measure the shapes of planar sections of the same crystals. A stereological analysis has been used to determine that {101¯0} prism facets and the {0001} basal planes are the WC surfaces that are most frequently in contact with Co. Further, the WC habit is an approximately equiaxed trigonal prism bound by three prism facets and two basal facets. An analysis of 15,600 grain boundaries shows that certain interfaces occur with a frequency that is much higher than would be expected in a random distribution and that the grain boundary habit planes also have {101¯0} and {0001} orientations. Eleven percent of all the observed WC-WC interfaces are 90° twist boundaries about [101¯0]. Two types of boundaries with a 30° rotation about [0001], a twist and an asymmetric tilt, comprise 3% of the population. 相似文献
5.
《Applied Surface Science》1987,28(4):429-438
Photoelectrochemical etching of CdTe produces etch pits of the same shape as obtained by selective chemical defect etching on the {111}, {100} and {110} faces. Their geometry is explained by atomic models of the surfaces. These new results extend our understanding of photoelectrochemical etching. They suggest that the interpretation of surface morphology should consider, in addition to the nonuniform charge flow through the semiconductor junction, the crystallographic effects on the development of the etch pits. 相似文献
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《Surface science》1992,279(3):L213-L218
After heat treatment at ∼1600 K and rapid quenching, thermal roughening through kink formation could be observed on “FEM-clean” Pt{110} and on all its vicinal areas (which are made up of {110} terraces). Noticeable exceptions were the areas between {771} and {331} (including {771}), which are located on the [1̄10] zone. These areas may remain topographically unchanged, or, more likely, may form {111}-microfacets during heat treatment. Upon annealing, the high-temperature roughness on {110} started to decrease at 830 K (formation of an 1 × 2 structure) and reached a minimum at 960 ± 25 K (≡ transition temperature, Tc). Thereafter, it increased precipitously until 1030 K was reached (surface roughening/deconstruction). Surface roughening could be suppressed readily by gas phase and/or bulk impurities (surface segregation). Vapour deposited Si, P, SiO, TiO2, Al2O3 and C (graphite) prevented surface roughening on Pt{110}. All investigations were carried out by FEM. 相似文献
7.
S. Abu Saleh 《哲学杂志》2013,93(26):3967-3980
Structure details of latent tracks created by U, Pb and Au ions (energies 6.9, 28.7 and 11.1?MeV/A, respectively) in {111} CaF2 have been extracted by means of scanning force microscopy and transmission electron microscopy. The revealed structure has assisted in the interpretation of the etching behaviour of tracks created in {111} CaF2 by 9.2?MeV/A Bi ions. In the latter experiments, irradiated fragments were immersed for short durations in a 3:1 10% HCl/96% H2SO4 solution and the morphology of the formed etch pits was derived by high-resolution scanning electron microscopy and scanning force microscopy. Three conclusions emerged. First, ion-induced surface hillocks exhibit no resistance against etchant attack. Second, the primary etching diameter of the track coincides with the nanometric width of the structurally altered track core. Third, the structure of the etch pits, 3-faced symmetric pyramidal depressions with {122} faces, indicates that etching across the track halo, a few tens of nanometers wide strained crystal, is dominated by surface energies of crystal faces. 相似文献
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《Surface science》1986,176(3):701-708
Investigations by field electron microscopy revealed that graphite{0;0001} layers grow preferentially on Pt{110}. Layer nucleation and initial growth occurs in the vicinal area of {110} along the 〈112〉 and the 〈100〉 zones and not on the unstepped {110} plane itself. The growth rate in the vicinal area is determined by the epitaxial misfit parallel to the step edges. An alignment of the graphite layer with the underlying {110} is observed. It corresponds to graphite〈101̄0〉 ∥ Pt〈100〉, which coincides with the calculated orientation of smallest epitaxial misfit. The change of relative emission from {110} upon adsorption of graphite is discussed. 相似文献
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Observation of regular defects formed on the surface of PbTe thin films grown by molecular beam epitaxy 总被引:1,自引:0,他引:1
Bingpo ZhangChunfeng Cai Lian HuXiaodong Wei Huizhen Wu 《Applied Surface Science》2011,257(6):1986-1989
Regular shape defects on the surface of PbTe thin films grown by molecular beam epitaxy (MBE) were studied by scanning electron microscope (SEM). Two types of regular shape defects were observed on Te-rich PbTe films grown at substrate temperature T ≥ 235 °C with a beam flux ratio of Te to PbTe (Rf) to be 0.5 and at 280 °C with a Rf ≥ 0.4, which include cuboids and triangular pyramids. The formation mechanism of the observed regular shape defects is interpreted as following: They are the outcome of fast growth rate along {1 0 0} crystal planes that have the lowest surface energy and the enclosure of the {1 0 0} crystal planes. The formation of the regular shape defects in the growth of PbTe needs appropriate substrate temperature and Te-rich ambience. However, when Rf is decreased low enough to make the films slightly Pb-rich, triangular pits that originate from the insufficient glide of the threading dislocations along the main 〈1 1 0〉 {1 0 0} glide system of PbTe in Cottrell atmosphere, will be the main feature on the film surface. 相似文献
10.
Zhenyang Zhong A. Halilovic H. Lichtenberger F. Schffler G. Bauer 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):243
We report on the growth and properties of Ge islands grown on (0 0 1) Si substrates with lithographically defined two-dimensionally periodic pits. After thermal desorption and a subsequent Si buffer layer growth these pits have an inverted truncated pyramid shape. We observe that on such prepatterned substrates lens-like Ge-rich islands grow at the pit bottoms with less Ge deposition than necessary for island formation on flat substrates. This is attributed to the aggregation of Ge at the bottom of the pits, due to Ge migration from the pit sidewalls. At the later stages of growth, dome-like islands with dominant {1,1,3} or {15,3,23}, or other high-index facets [i.e. {15,3,20} facets] are formed on the patterned substrates as shown by surface orientation maps using atomic force microscopy. Furthermore, larger coherent islands can be grown on patterned substrates as compared to Ge deposition on flat ones. 相似文献
11.
The structural aspect of the formation of Ni(CO)4 by the reaction of CO with solid nickel has been studied. The nickel initial state was a nearly hemispherical single crystal as prepared by field evaporation of a nickel field emitter tip. Field-free reaction of CO with the clean nickel surface took place at pressures up to 2 mbar, reaction times up to 45 h, and at a temperature of 373 K, which as a result from work by others was found optimum for highest rates of Ni(CO)4 formation. Neon field ion imaging at 80 K after reaction with CO showed the crystal always in an intermediate state, which had the features: (1) Areas of {;111} were increased; (2) at half angles between a central (111) and peripherical {111} planes there were {110} planes flanked by {210}, and {100} flanked by {511}, respectively; (3) with the exception of the planes mentioned in feature (2), the remaining surface area was more than mono-atomically stepped. From these results and in accordance with the theory of crystal growth (Kossel, Stranski) and the theory of crystal dissolution (Lacmann, Franke, Heimann) a pure octahedron is expected to be the final state of the crystal. This implies that nickel atoms removed by the reaction are most frequently taken from 〈110〉 atom chains of the {111} planes. 相似文献
12.
M. Tamura Y. Hiroyama A. Nishida M. Horiuchi 《Applied Physics A: Materials Science & Processing》1998,66(4):373-384
14 /cm2 dose of As ions followed by both isochronal and isothermal annealing. The elementary defects generated first during solid-phase
epitaxial recovery of implantation-induced amorphous layers at temperatures of 550 °C and/or 600 °C are {311} defects 2–3 nm
long. They are considered to be transformed into {111} and {100} defects after annealing at temperatures higher than 750 °C.
These secondary defects show the opposite annealing behavior to the dissolution and growth by the difference of their depth
positions at 800 °C. This phenomenon is explained by the diffusion of self-interstitials contained in defects. With regard
to the formation and dissolution of defects, there is no significant difference between the effects of rapid thermal annealing
(950 °C for 10 s) and furnace annealing (800 °C for 10 min).
Received: 14 November 1997/Accepted: 16 November 1997 相似文献
13.
J. Moc 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(2):397-402
We have studied the interaction of Al13-_{13}^{-} anion
cluster with H2. Both the long range interaction and dissociative
adsorption have been examined using the established correlated ab initio
methods, MP2 and CCSD(T), in conjunction with the augmented correlation
consistent basis sets up to aug-cc-pVTZ. The formation of the weakly bound
(physisorbed) end-on anion complex Al13-_{13}^{-}...H2 is
predicted for the interacting Al...H distances of 3.95 ? with the
H-H axis pointing towards the ‘hollow’ site of Al13-_{13}^{-} and binding
energy (De)D_{e}) of 0.7 kcal/mol at the estimated complete basis set (CBS)
limit of CCSD(T). The barrier height for H2 dissociation on
Al13-_{13}^{-} of 41.6 (42.9) kcal/mol calculated at the ZPVE-corrected
CCSD(T)/aug-cc-pVTZ (estimated CCSD(T)/CBS) level is at least twice as large
as that evaluated by us for a dissociative adsorption of H2 on an
open-shell Al13 neutral cluster. To our knowledge, this report presents
the first “benchmark” quality study of the physisorption and dissociative
chemisorption of molecular hydrogen on Al13-_{13}^{-} anion cluster. 相似文献
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Formation energies for Ge/Si(100) pyramidal islands are computed combining continuum calculations of strain energy with first-principles-computed strain-dependent surface energies. The strain dependence of surface energy is critically impacted by the presence of strain-induced changes in the Ge {100} surface reconstruction. The appreciable strain dependencies of rebonded-step {105} and dimer-vacancy-line-reconstructed {100} surface energies are estimated to give rise to a significant reduction in the surface contribution to island formation energies. 相似文献
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Effect of dislocations on the shape of islands during silicon growth on the oxidized Si(111) surface
The formation of dislocation-rich and dislocation-free silicon islands during growth in the absence of mechanical stresses
has been studied by scanning tunneling microscopy. The rounded shape of islands obtained at growth temperatures of 400–500°C
on the oxidized Si(111) surface is associated with the presence of dislocations within them. The transfer of atoms from the
oxidized surface to the islands occurs due to the barrier of the potential energy at the SiO2/Si boundary. The {111} and {311} facets dominate in the shape of the islands grown at 500–550°C. Their appearance indicates
the absence of the threading dislocations in the islands and that the growth is limited by the stage of the nucleation of
a new atomic layer. 相似文献
17.
PbSe thin films on BaF2 (1 1 1) were grown by molecular beam epitaxy with different selenium beam flux. Evolution of PbSe surface morphologies with Se/PbSe beam flux ratio (Rf) has been studied by atomic force microscopy and high-resolution X-ray diffraction. Growth spirals with monolayer steps on PbSe surface are obtained using high beam flux ratio, Rf ≥ 0.6. As Rf decreases to 0.3, nano-scale triangle pits are formed on the surface and the surface of PbSe film changes to 3D islands when Rf = 0. Glide of threading dislocations in 〈1 1 0〉{1 0 0}-glide system and Pb-rich atom agglomerations are the formation mechanism of spiral steps and triangle pits. The nano-scale triangle pits formed on PbSe surface may render potential applications in nano technology. 相似文献
18.
S Zhou YA Nastishin MM Omelchenko L Tortora VG Nazarenko OP Boiko T Ostapenko T Hu CC Almasan SN Sprunt JT Gleeson OD Lavrentovich 《Physical review letters》2012,109(3):037801
Using a magnetic Frederiks transition technique, we measure the temperature and concentration dependences of splay K_{1}, twist K_{2}, and bend K_{3} elastic constants for the lyotropic chromonic liquid crystal sunset yellow formed through noncovalent reversible aggregation of organic molecules in water. K_{1} and K_{3} are comparable to each other and are an order of magnitude higher than K_{2}. At higher concentrations and lower temperatures, K_{1} and the ratios K_{1}/K_{3} and K_{1}/K_{2} increase, which is attributed to elongation of self-assembled lyotropic chromonic liquid crystal aggregates, a feature not found in conventional thermotropic and lyotropic liquid crystals formed by covalently bound units of a fixed length. 相似文献
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The near-interface region of an epitaxial Ba0.3Sr0.7TiO3 thin film grown on LaAlO3 (001) was found to consist of a high density of ½?110? stacking faults bounded by partial dislocations. The stacking faults can extend over large distances (greater than 50 nm). Various possible atomic configurations of the faults were considered. The atomic structures of the faults were identified using high-resolution electron microscopy and simulation as well as energy-filtered imaging. The ½[101] and faults (where [001] is normal to the film plane) were found to lie predominately on the {100} and {110} planes. The ½lsqb;101] faults on (010), (110) or (1&1tilde;0) have never been observed before in perovskites. The stacking faults on [100] have a structure consisting of a double layer of edge-sharing TiO6 octahedra. The excess of Ti was detected by energy-filtered imaging. The formation of the extended stacking faults is probably related to a small amount of excess Ti during the film deposition, which may originate from the non-stoichiometry of the ceramic targets BaTiO3 and SrTiO3. It is also enhanced by the misfit-induced compressive strain in the early stages of the film growth. 相似文献