Showing papers on "Crystal published in 1998"
TL;DR: In this article, the authors constructed a 3D infrared photonic crystal on a silicon wafer using relatively standard microelectronics fabrication technology, which showed a large stop band (10−14.5μm), strong attenuation of light within this band (∼12 dB per unit cell) and a spectral response uniform to better than 1 per cent over the area of the 6-inch wafer.
Abstract: The ability to confine and control light in three dimensions would have important implications for quantum optics and quantum-optical devices: the modification of black-body radiation, the localization of light to a fraction of a cubic wavelength, and thus the realization of single-mode light-emitting diodes, are but a few examples1,2,3. Photonic crystals — the optical analogues of electronic crystal — provide a means for achieving these goals. Combinations of metallic and dielectric materials can be used to obtain the required three-dimensional periodic variations in dielectric constant, but dissipation due to free carrier absorption will limit application of such structures at the technologically useful infrared wavelengths4. On the other hand, three-dimensional photonic crystals fabricated in low-loss gallium arsenide show only a weak ‘stop band’ (that is, range of frequencies at which propagation of light is forbidden) at the wavelengths of interest5. Here we report the construction of a three-dimensional infrared photonic crystal on a silicon wafer using relatively standard microelectronics fabrication technology. Our crystal shows a large stop band (10–14.5 μm), strong attenuation of light within this band (∼12 dB per unit cell) and a spectral response uniform to better than 1 per cent over the area of the 6-inch wafer.
1,052 citations
TL;DR: In this article, the topmost oxide layer was observed to hydroxylate after immersion in water, which was used to enhance the etch-selectivity of SrO relative to TiO2 in a buffered HF solution.
Abstract: In recent years, well-defined and nearly perfect single crystal surfaces of oxide perovskites have become increasingly important. A single terminated surface is a prerequisite for reproducible thin film growth and fundamental growth studies. In this work, atomic and lateral force microscopy have been used to display different terminations of SrTiO3. We observe hydroxylation of the topmost SrO layer after immersion of SrTiO3 in water, which is used to enhance the etch-selectivity of SrO relative to TiO2 in a buffered HF solution. We reproducibly obtain perfect and single terminated surfaces, irrespective of the initial state of polished surfaces and the pH value of the HF solution. This approach to the problem might be used for a variety of multi-component oxide single crystals. True two-dimensional reflection high-energy electron diffraction intensity oscillations are observed during homo epitaxial growth using pulsed laser deposition on these surfaces.
693 citations
Book•
01 Jan 1998TL;DR: In this article, the authors describe the morphology of a crystal surface and the equilibrium crystal shape, including growth and dissolution of a planar front and growth roughness at long length scales in linear approximation.
Abstract: Preface List of symbols 1. Morphology of a crystal surface 2. Surface free energy, step free energy, and chemical potential 3. The equilibrium crystal shape 4. Growth and dissolution crystal shapes: Frank's model 5. Crystal growth: the abc 6. Growth and evaporation of a stepped surface 7. Diffusion 8. Thermal smoothing of a surface 9. Silicon and other semiconducting materials 10. Growth instabilities of a planar front 11. Nucleation and the adatom diffusion length 12. Growth roughness at long lengthscales in the linear approximation 13. The Kardar-Parisi-Zhang equation 14. Growth without evaporation 15. Elastic interactions between defects on a crystal surface 16. General equations of an elastic solid 17. Technology, crystal growth and surface science Appendices References Index.
635 citations
TL;DR: In this article, the elastic anisotropy in these artificial dot crystals acts in a manner similar to that of the directed chemical bonds of crystalline solids, which may be advantageous for optoelectronic device applications.
Abstract: The self-organization of pyramidal PbSe islands that spontaneously form during strained-layer epitaxial growth of PbSe/Pb1−xEuxTe (x = 0.05 to 0.1) superlattices results in the formation of three-dimensional quantum-dot crystals. In these crystals, the dots are arranged in a trigonal lattice with a face-centered cubic (fcc)–like A-B-C-A-B-C vertical stacking sequence. The lattice constant of the dot crystal can be tuned continuously by changing the superlattice period. As shown by theoretical calculations, the elastic anisotropy in these artificial dot crystals acts in a manner similar to that of the directed chemical bonds of crystalline solids. The narrow size distribution and excellent control of the dot arrangement may be advantageous for optoelectronic device applications.
397 citations
TL;DR: In this paper, the piezoelectric and dielectric constants in different crystal orientations of the lead zirconate titanate (PZT) have been phenomenologically calculated for the compositions near the morphotropic phase boundary at room temperature.
Abstract: The piezoelectric and dielectric constants in different crystal orientations of the lead zirconate titanate (PZT) have been phenomenologically calculated for the compositions near the morphotropic phase boundary at room temperature. For a tetragonal PZT, the effective piezoelectric constant d33 monotonously decreases as the crystal cutting angle from the spontaneous polarization direction [001] increases. However, for a rhombohedral PZT, the effective piezoelectric constant d33[001]// along the perovskite [001] direction was found to be much larger than those along the spontaneous polarization direction [111]. This crystal orientation-related enhancement is emphasized as the composition approaches the morphotropic phase boundary. This suggests that by adopting the perovskite [001] orientation with a rhombohedral composition near the morphotropic phase boundary, the piezoelectric constant d33 for PZT can be greatly enhanced.
393 citations
TL;DR: In this article, the properties of the isostructural compound β-HfNCl have been investigated and shown to have superconductivity with a Tc of up to 25.5 K.
Abstract: The electronic properties of crystals with a layered structure can be radically altered by the intercalation, between the layers, of guest species that act as electron donors or acceptors. Such studies have been performed extensively on graphite, transition-metal dichalcogenides and oxide bronzes1. Interest in redox intercalation reactions2 has increased recently because the high-transition-temperature (high-Tc) superconductors based on copper oxide also have layered structures, the superconductivity occurring within two-dimensional CuO2 planes separated by charge-reservoir oxide layers3. Similarly, in metal-doped fullerenes, which show relatively high transition temperatures, the electron donor atoms sit in the interstitial sites between adjacent fullerene balls4. In a previous study5, we described a layered nitride, β-ZrNCl, consisting of Zr–N double layers sandwiched between two close-packed chlorine layers. On lithium intercalation, the crystal changed from a semiconductor to a metal, and became a superconductor at 13 K. Here we report the properties of the isostructural compound β-HfNCl. After electron-doping the crystal by lithium intercalation, we observe superconductivity with a Tc of up to 25.5 K. This transition temperature is higher than that observed in any intermetallic compound, and suggests that layered nitride structures may offer transition temperatures comparable to those observed in layered copper oxide structures.
366 citations
TL;DR: In this paper, the structure, optical and electrical properties of ZnO films were investigated, and the c-axis lattice constants of the thin films and the band gap were shown to be a little larger than those of the crystal. But the differences between the thin film and crystal might be attributable to the grain boundaries and imperfections in thin films.
361 citations
TL;DR: In this paper, the authors present a program for the calculation of the frequency band structure of an infinite photonic crystal, and of the transmission, reflection and absorption coefficients of light by a slab of this crystal.
334 citations
TL;DR: In this article, crystal ion slicing was used to create a buried sacrificial layer in single-crystal c-cut poled wafers of LiNbO3, inducing a large etch selectivity between the sacrificial layers and the rest of the sample.
Abstract: We report on the implementation of crystal ion slicing in lithium niobate (LiNbO3). Deep-ion implantation is used to create a buried sacrificial layer in single-crystal c-cut poled wafers of LiNbO3, inducing a large etch selectivity between the sacrificial layer and the rest of the sample. 9-μm-thick films of excellent quality are separated from the bulk and bonded to silicon and gallium arsenide substrates. These single-crystal films have the same room-temperature dielectric and pyroelectric characteristics, and ferroelectric transition temperature as single-crystal bulk. A stronger high-temperature pyroelectric response is found in the films.
306 citations
TL;DR: In this article, it was shown conclusively that the internal field originates from nonstoichiometric point defects in LiNbO3 crystals, and that the switching fields required for 180° domain reversal in congruent crystals [C=Li2O/(Li 2O+Nb2O5)=0484] are ∼4-5 times larger than the switching field for nearstoichometric crystals (C=0498).
Abstract: We show here conclusively that the internal field originates from nonstoichiometric point defects in LiNbO3 crystals The switching fields required for 180° domain reversal in congruent crystals [C=Li2O/(Li2O+Nb2O5)=0484] are ∼4–5 times larger than the switching fields for nearstoichiometric crystals (C=0498) An internal field of ∼25 kV/mm observed in congruent crystals disappears in stoichiometric crystals The concentration of hydrogen incorporated during crystal growth has no effect on the switching or internal fields The measured spontaneous polarization, Ps=80±5 μC/cm2 is relatively insensitive to the crystal nonstoichiometry and the hydrogen content
297 citations
Journal Article•
TL;DR: In this paper, an improved Monte Carlo/ray-tracing method has been developed to compute the single-scattering parameters for these complex ice crystals, in particular, those with fernlike structures, scatter more energy in the angular region 2°-20° and in the lateral and backward directions than hexagonal ice crystals.
Abstract: Various ice crystal shapes including fernlike geometry, plates with dendritic extensions and with sector-like and broad branches, fractal geometry, and aggregates, have been numerically defined on the basis of available observations. The surface roughness of ice crystals is also accounted for by specifying the facet-tilt distribution in terms of Gram Charlier series for the small facets of which the rough surface consists. These ice crystal geometries along with those defined in our previous studies may approximately represent the ice crystal shapes frequently observed in cirrus clouds. An improved Monte Carlo/ray-tracing method has been developed to compute the single-scattering parameters for these complex ice crystals. The polarization configurations of the localized waves associated with Fresnelian rays are comprehensively accounted for by the improved method in ray-tracing procedure. Complex ice crystals, in particular, those with fernlike structures, scatter more energy in the angular region 2°-20° and in the lateral and backward directions than hexagonal ice crystals. The former ice crystal geometries normally produce smaller polarization values. In particular, a substantial reduction for the negative polarization associated with the backscattering is found as a result of the complex crystal geometries. The surface roughness of ice crystals incorporated into the single-scattering calculation tends to smooth out the scattering peaks corresponding to halos. The roughness also significantly reduces the backscattering. When a substantial roughness condition is imposed, the computed phase function and the polarization configuration of scattered light are essentially featureless. A database of the single-scattering parameters of ice crystals at solar wavelengths covering 0.2-5 μm has been established for various ice crystal shapes and sizes. This database can be useful in the parameterization of the bulk radiative properties of cirrus clouds to account for the effects of ice crystal size distribution and the percentage of various crystal habits. By applying this database to cold and warm cirrus clouds, it is demonstrated that the scattering and absorption characteristics of these clouds depend on both the size distribution and the shapes of ice crystals.
TL;DR: In this paper, the authors used a double crucible Czochralski method to grow LiTaO3 single crystals with a composition close to stoichiometry by using a double-crazed double-branched crystal Czarnecki method and compared the switching field required for 180° ferroelectric domain reversal and the internal fields originating from nonstoichiometric point defects for the stoichiometric and conventional commercially available crystals.
Abstract: We grew LiTaO3 single crystals with a composition close to stoichiometry by using a double crucible Czochralski method. The switching field required for 180° ferroelectric domain reversal and the internal fields originating from nonstoichiometric point defects were compared for the stoichiometric and conventional commercially available crystals. The switching fields for the domain reversal in the stoichiometric crystal with a Curie temperature of 685 °C was 1.7 kV/mm. This is about one thirteenth of the switching field required for the conventional LiTaO3 crystals with a Curie temperature near 600 °C. The internal field in the stoichiometric crystal drastically decreased to 0.1 kV/mm.
TL;DR: The potential of using a quartz crystal microbalance based technique for the characterization of living cells during the process of adhesion to a surface and the evolution of the dissipation factor in combination with resonant frequency is explored.
Abstract: We explore the potential of using a quartz crystal microbalance based technique for the characterization of living cells during the process of adhesion to a surface. The combined information from s...
Patent•
27 May 1998
TL;DR: In this paper, an amorphous semiconductor thin film is crystallized by utilizing a catalyst element, the catalyst element is removed by performing a heat treatment in an atmosphere containing a halogen element.
Abstract: After an amorphous semiconductor thin film is crystallized by utilizing a catalyst element, the catalyst element is removed by performing a heat treatment in an atmosphere containing a halogen element. A resulting crystalline semiconductor thin film exhibits {110} orientation. Since individual crystal grains have approximately equal orientation, the crystalline semiconductor thin film has substantially no grain boundaries and has such crystallinity as to be considered a single crystal or considered so substantially.
TL;DR: In this article, an X-ray diffraction investigation has been made of the crystal structure to determine the distribution of hydrogen bonds, to understand the crystalline thermal expansion and to determine influence of water on the polymer crystals and crystallisation process.
TL;DR: In this paper, a birefringent α-BaB 2 O 4 crystal, 40mm in diameter, 35mm in height has been grown successfully in a laboratory by Czochralski method.
TL;DR: In this article, a combination of in situ observations of growth mechanisms at molecular resolution with the atomic force microscope and computer simulations of the surface attachment of growth units is used to compare the limitations of both the Burton-Cabrera-Frank (BCF) and periodic-bond-chain (PBC) theories in providing a general description of crystal growth.
Abstract: Models of crystal growth have been defined by comparing macroscopic growth kinetics with theoretical predictions for various growth mechanisms1,2 The classic Burton–Cabrera–Frank (BCF) theory3 predicts that spiral growth at screw dislocations will dominate near equilibrium Although this has often been observed2,4, such growth is sometimes inhibited4,5, which has been assumed to be due to the presence of impurities6 At higher supersaturations, growth is commonly modelled by two-dimensional nucleation on the pre-existing surface according to the ‘birth and spread’ model7 In general, the morphology of a growing crystal is determined by the rate of growth of different crystallographic faces, and periodic-bond-chain (PBC) theory8,9 relates this morphology to the existence of chains of strongly bonded ions in the structure Here we report tests of such models for the growth of barite crystals, using a combination of in situ observations of growth mechanisms at molecular resolution with the atomic force microscope10,11 and computer simulations of the surface attachment of growth units We observe strongly anisotropic growth of two-dimensional nuclei with morphologies controlled by the underlying crystal structure, as well as structure-induced self-inhibition of spiral growth Our results reveal the limitations of both the BCF and PBC theories in providing a general description of crystal growth
TL;DR: In this article, the authors examined the structure and dynamics of the face-centered cubic (100) and (111) crystal-melt interfaces for systems consisting of approximately 104 hard spheres using molecular dynamics simulation.
Abstract: In this work, we examine in detail the structure and dynamics of the face-centered cubic (100) and (111) crystal–melt interfaces for systems consisting of approximately 104 hard spheres using molecular dynamics simulation. A detailed analysis of the data is performed to calculate density, pressure, and stress profiles (on both fine and coarse scales), as well as profiles for the diffusion and orientational ordering. The strong dependence of the coarse-grained profiles on the averaging procedure is discussed. Calculations of 2-D density contours in the planes perpendicular to the interface show that the transition from crystal to fluid occurs over a relatively narrow region (over only 2–3 crystal planes) and that these interfacial planes consist of coexisting crystal- and fluidlike domains that are quite mobile on the time scale of the simulation. We also observe the creation and propagation of vacancies into the bulk crystal.
TL;DR: In this article, a series of 2,4,6-triaryloxy-1,3,5-triazines, 1−6, are reported to consistently form quasi-trigonal or trigonal networks that are two-dimensionalally non-centrosymmetric.
Abstract: The principles of crystal engineering have been used to design a family of structures with potential as octupolar nonlinear optical (NLO) materials. The major aim in such an exercise, a carry-over of molecular symmetry into the crystal, is possible with a retrosynthetic approach. An appropriate choice of precursor trigonal molecules leads from the concept of the dimeric Piedfort unit. The crystal structures and NLO properties of a series of 2,4,6-triaryloxy-1,3,5-triazines, 1−6, are reported. These compounds consistently form quasi-trigonal or trigonal networks that are two-dimensionally noncentrosymmetric. Substitutional variations on the phenyl moieties that were expected to maintain or to perturb this trigonal network have been explored. Molecular nonlinearities have been measured by Harmonic Light Scattering (HLS) experiments. Among the compounds studied, 2,4,6-triphenoxy-1,3,5-triazine, 1 adopts a noncentrosymmetric crystal structure with a measurable SHG powder signal. All these crystal structures a...
TL;DR: In this article, a narrow crystal size distribution and retardation of growth parallel to [001] are observed in dependence on the concentration of the block copolymer, which is added in the ppm range.
Abstract: Amphipolar diblock copolymers used as admixtures provide a unique effect on crystallization processes from solution. In an example given here, nucleation of ZnO crystals and growth of specific crystal faces is controlled by minute amounts of PEO-b-PMAA copolymers. A narrow crystal size distribution and retardation of growth parallel to [001] are observed in dependence on the concentration of the block copolymer, which is added in the ppm range.
01 May 1998-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the microstructure and physical properties of 6H-SiC amorphized by both ion and neutron irradiation were analyzed using high-resolution transmission electron microscopy (HRTEM).
Abstract: This paper presents results on the microstructure and physical properties of SiC amorphized by both ion and neutron irradiation. Specifically, 0.56 MeV Si ions have been implanted in single crystal 6H–SiC from ambient through >200°C and the critical threshold for amorphization was measured as a function of the irradiation temperature. From a high resolution transmission electron microscopy (HRTEM) study of the crystalline to amorphous transition region in these materials, elongated pockets of amorphous material oriented parallel to the free surface are observed. Single crystal 6H–SiC and hot pressed and sintered 6H and 3C SiC were neutron irradiated at approximately 70°C to a dose of ∼2.56 dpa causing complete amorphization. Property changes resulting from the crystal to amorphous transition in SiC include a density decrease of 10.8%, a hardness decrease from 38.7 to 21.0 GPa, and a decrease in elastic modulus from 528 to 292 GPa. Recrystallization of the amorphized, single crystal 6H–SiC appears to occur in two stages. In the temperature range of ∼800–1000°C, crystallites nucleate and slowly grow. In the temperature range of 1125–1150°C spontaneous nucleation and rapid growth of crystallites occur. It is further noted that amorphized 6H (alpha) SiC recrystallizes to highly faulted fcc (beta) SiC.
TL;DR: In this paper, a complete interpretation for the pre-edge fine structure (PEFS) of the x-ray Ti K-absorption spectra for perovskite structure crystals is proposed based on the results of numerous calculations performed by a modified full multiple scattering method.
Abstract: A complete interpretation is proposed for the pre-edge fine structure (PEFS) of the x-ray Ti K-absorption spectra for perovskite structure crystals. The interpretation is based on the results of numerous calculations performed by a modified full multiple scattering method which provides the theoretical spectra for the 3d transition metal oxides in fair agreement with experiment. It is shown that the three main peaks in the PEFS have quite different origin. The first long-wave side peak A is caused mainly by quadrupole transitions. The middle peak B is caused by the p-d mixture effect and the high intensity of it is considered to be a qualitative spectroscopic indication of ferroelectricity in the perovskite structure crystal. A simple formula is obtained which expresses the area under peak B through the lattice constants and mean-square displacement of the absorbing Ti atom from the instantaneous centre of the coordination polyhedron. The peak B area averaged over thermal atomic vibrations is determined by the three-particle atomic distribution function. The short-wave side peak C is caused by the Ti 1s electron transition to the unoccupied 3d states of the neighbouring transition metal atoms. We show that an additional peak on the short-wave side of peak C occurs if there are 4d atoms (for instance Zr atoms in the vicinity of the absorbing Ti atom in the (PZT) solid solution) within the oxygen atom octahedrons surrounding the absorbing 3d atom. The area under peak is directly determined by the average number of 4d atoms in the vicinity of the absorbing Ti one.
TL;DR: The data indicate that the experimental approach can be successfully used to prepare nanoapatite with crystallinity, crystal dimensions, composition, structure and stability very close to those characteristics of biological apatites.
TL;DR: In this paper, the authors investigated the Raman spectra of B-doped diamond crystals grown by microwave plasma assisted chemical vapor deposition as a function of boron concentration and found that the asymmetry and broadening of the one-phonon are due to Fano interference.
TL;DR: In this paper, a morphological survey on new PBO fiber (Zylon®) was conducted by X-ray and transmission electron microscopic studies, which revealed that the molecule in the fiber showed high orientation (more than 0.99 in Hermann's orientation function for heat-treated fiber) and relatively small crystal sizes in the longitudinal and transverse directions.
Abstract: Morphological survey on new PBO fiber (Zylon®) was conducted by X-ray and transmission electron microscopic studies. Crystal size, orientation of the crystal, fibrils, microvoids, and fine structure were discussed. It was found that the molecule in the fiber showed high orientation (more than 0.99 in Hermann's orientation function for heat-treated fiber) and relatively small crystal sizes in the longitudinal (160 A) and the transverse (110 A) directions. Crystal modulus estimated by extrapolation to perfect orientation on the plot of the fiber modulus as a function of fiber orientation (Northolt's method) shows discrepancy from the crystal modulus directly obtained by X-ray scattering. This discrepancy means that the Northolt's model is insufficient to describe the Young's modulus of PBO fiber. Microvoids elongated to the fiber direction were examined by small-angle X-ray scattering and transmission electron microscopic methods. The diameter of the microvoids was 20 A to 30 A and the fiber had a very thin microvoids-free layer (0.2 μm). Preferential orientation of the a-axis of crystal in the fiber was also confirmed. Summarizing these results, a structure model of the PBO fiber was proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 39–48, 1998
TL;DR: Based on the anionic group theory of nonlinear optical crystals and the relationship between the microscopic nonlinear coefficients of anionic groups and the macroscopic coefficients of the crystal, an evaluation system has been established to analyze the spatial arrangement of the ion groups in a crystal lattice as discussed by the authors.
Abstract: Based on the anionic group theory of nonlinear optical crystals and the relationship between the microscopic nonlinear coefficients of the anionic group and the macroscopic coefficients of the crystal, an evaluation system has been established to analyze the spatial arrangement of the anionic groups in a crystal lattice. A structural criterion is given to find which crystal has a favorable spatial arrangement of the anionic groups in terms of its nonlinear effects. Some of the currently available nonlinear optical crystals have been analyzed in this way with a computer program to test the evaluation method, and results demonstrate that the above structural criterion is quite reliable. Several compounds with crystallographic data from an inorganic crystal structure database were evaluated and found to be possible good candidates for nonlinear applications.
TL;DR: In this article, a method for estimating site types and ionizable site densities at mineral surfaces by consideration of ideal crystal surfaces has been developed, and the predicted site types with respect to the interpretation of infrared data and for improving adsorption and dissolution rate models are discussed.
Abstract: In this study, a method for estimating site types and ionizable site densities at mineral surfaces by consideration of ideal crystal surfaces has been developed. Periclase, rutile, goethite, hematite, corundum, kaolinite, andalusite, sillimanite, sanidine, albite, anorthite, and quartz surfaces were considered, both because they represent a wide range of crystal structures and because many adsorption and dissolution studies have focused on these minerals. For each mineral, the predominant cleavage or growth faces were studied. To avoid choosing arbitrary slices of the crystal parallel to each cleavage or growth face, the total Brown bond strengths (and the resulting partial charges on coordinatively unsaturated atoms) were calculated for the bonds that must be broken to generate each possible ideal slice on a given plane. The charge-neutral or nearly charge-neutral slices produced with a minimum total strength of bonds severed were examined with the aid of the commercial computer program Crystal-Maker C . Once the ideal mineral surface for a given plane was chosen, the number of sites per unit surface area was calculated using five different methods. For the minerals considered, calculated site densities for a given surface ranged from 0 to 40.8 sites/nm 2 , a considerably larger range than the density of 2.3 to 10 sites/nm 2 that is often cited. The results from each of the methods were compared to available experimental estimates of surface hydroxyl site densities from temperature desorption experiments, infrared data, and tritium exchange methods and to ionizable or reactive site densities from acid-base titrations and chemical reaction methods. Estimates based on the number of broken bonds gave the best agreement with site densities using the tritium exchange method. However, estimates based on the number of coordinatively unsaturated atoms or on the partial charge of coordinatively unsaturated atoms were also consistent with much of the available tritium exchange data. Predicted site types were compared with the available spectroscopic data. Implications of predicted site types with respect to the interpretation of infrared data and for improving adsorption and dissolution rate models are discussed.
TL;DR: In this article, a large single crystal (6mmO × 50 mm) of YbB12 was grown by floating zone method using a newly developed image-furnace with four xenon lamps.
TL;DR: In this article, the surface morphology of a Cu(110) crystal, generated by ion sputtering, has been investigated by scanning tunneling microscopy, and the results are described by a continuum equation which includes both surface curvature dependent erosion terms and diffusion terms accounting for surface anisotropy and Ehrlich-Schwoebel barriers.
Abstract: Surface morphology of a Cu(110) crystal, generated by ion sputtering, has been investigated by scanning tunneling microscopy. Different from recent theoretical predictions and experimental results, normal sputtering produces a well defined ripple structure whose wave vector rotates from $〈001〉$ to $〈1\overline{1}0〉$ by increasing the substrate temperature. Off-normal sputtering at low temperature (180 K) generates ripples whose orientation depends on both ion direction and surface azimuthal orientation. These results are described by a continuum equation which includes both surface curvature dependent erosion terms and diffusion terms accounting for surface anisotropy and Ehrlich-Schwoebel barriers.