Observation Of Surface Topography Research Articles

Fractal analysis of roughness profile induced by ion bombardment of metal surface

Surface roughness, which plays or could play an important role in microelectronics, surface analysis, medicine and other branches of science and technology, is one of the more important aspects of ion bombardment-induced modification of surface morphology of solids. The results of profilometric and microscopic experiments showed dependence of measured surface roughness parameters upon the length of elementary segment (profilograph) or scanning area (AFM). The “scaling effects” are interesting and may be important in fractal analysis of ion sputtered surface. The paper presents an analysis in question relative to stainless-steel surface roughness profile generated by very oblique broad argon ion beam irradiation. The preliminary results obtained for normal bombardment and presented elsewhere have shown that fractal analysis, surface roughness measurement and surface topography observations may form a proper investigative tool which could give a relatively full picture of surface morphology modification during ion beam bombardment. Here, we tried to verify this conclusion for grazing incidence.

AFM observation of surface topography of fibre Bragg gratings fabricated in germanium–boron codoped fibres and hydrogen-loaded fibres

This paper reports the measurement of the surface topology of optical fibres containing a fibre Bragg grating (FBG) using an atomic force microscope (AFM). The AFM observation was made on FBGs fabricated via the phase mask technique in germanium–boron codoped optical fibres, in hydrogen-loaded germanium–boron codoped fibres and in standard telecommunications optical fibres. The surface images reveal that a spatial corrugation pattern was induced by the UV-irradiation, with a period that is half of the period of the phase mask. This UV-induced surface structure was found only on the side of the fibre facing towards the incident UV-irradiation and did not appear on the rear surface. The AFM probe scanned a 10×10 μm 2 surface area at seven sites along the 6.0 mm length of fibre that was exposed to the UV-irradiation. The amplitude of the spatial corrugation pattern observed on the AFM image was quantified for each site. It was found that the amplitude in a range of 0.7–3.2 nm was a function of UV-laser intensity distribution and the type of fibre. Hydrogen loaded optical fibres exhibited a corrugation with an amplitude twice as large as that observed in the Ge–B doped fibres that were not hydrogen-loaded. This correlates with the increase in photosensitivity produced by the hydrogen loading. A similar UV-induced spatial corrugation was also observed on standard telecom fibres, but without inducing the refractive index change in the fibre core. The observation of surface topology provides an insight into the structural changes induced during FBG fabrication. UV-induced densification and laser ablation could account for the formation of the surface troughs.

Fractography - Observing, Measuring and Interpreting Fracture Surface Topography

1. Introduction to the concepts used in the observation, measurement and interpretation of fracture surface topography 2. Observing, describing and measuring fracture surface topography: some basics using Ketton stone as an example 3. Tilting cracks 4. River line patterns 5. Mirror, mist and hackle: surface roughness, crack velocity and dynamic stress intensity 6. Cleavage of crystalline solids 7. Fracture at interfaces 8. Aspects of ductile fracture 9. Crack dynamic effects 10. Applications of fractography Appendix.

Investigation of oxidation process on plasma treated thin Al-films by GIXR and GIXRD

The sensitivity of grazing incidence X-ray reflectometry (GIXR) for amorphous as well as crystalline layers and for layer formations in the nm-range combined with information about structural states by grazing incidence X-ray diffractometry (GIXRD) enable these methods to study interfaces and surface layers. Thin aluminium layers (30–60 nm) were deposited on Si by thermal evaporation. These Al-layers were plasma oxidized for 5 h with interruptions every hour. The plasma treatments were carried out in a 2.45 GHz microwave discharge (SLAN-slot antenna) with different plasma types (Ar, O2) at low temperatures. In this way a thin oxide layer additional to the native alumina on the top was formed. The properties of the oxide layers such as thickness, roughness and density were studied by GIXR. The chemical composition was investigated by GIXRD and XPS. In addition AFM was used for surface topography observations. All these methods were applied before and after the plasma treatment. The properties of the thin Al-oxide layers were found to depend on the type of plasma but in all cases plasma leads to a smoothing of the films as well as an increasing of the thickness of the upper alumina layer.

Fatigue Properties and Dislocation Structures of Nitrided SS 400.

Fatigue properties of the nitrided SS 400 are investigated on the basis of the observation of dislocation structures, surface topography and fracture surface by means of optical and electron microscopy. Both slip bands and dislocation structures during stress cycling are not formed in the compound layer. The dislocation morphology of the diffusion layer is composed of the untangled and uniformly distributed dislocations and the clusters of the dislocation dipoles at lower stress amplitude, but well defined cell structures at higher stress amplitude. It is also found that the fatigue cracks of the nitrided specimen are initiated without the formation of slip bands and the separation between the compound layer and the diffusion layer occurs during cyclic loading. On the basis of these observations, a mechanism of fatigue fracture for the nitrided SS 400 is proposed.

Study of the low stress plasticity in single-crystal MgO by nanoindentation and atomic force microscopy

Berkovich nanoindentations have been performed at ambient temperature with a new apparatus on (001) cleaved surfaces of single-crystal Magnesium Oxide (MgO). Rosette slip lines pattern has been observed at a nanometric scale by Atomic Force Microscope. Moreover, the load-displacement curves present particular features such as pop-in, which has been linked to the AFM surface topography observations. Finally, we show that the combination of a new nanoindentation apparatus and an Atomic Force Microscope allows to study the very early stages of the plastic deformation during a nanoindentation in terms of individual dislocations.

Surface hydrogen densities of variously treated CVD diamond surfaces

Hydrogen, deuterium and oxygen densities on diamond (100) surfaces have been investigated by elastic recoil detection analysis (ERDA) and Rutherford backscattering spectrometry (RBS). The (100) surfaces were homoepitaxially grown by chemical vapor deposition (CVD), and surface reactions were enhanced by radical-beam treatments. Atomic force microscopy (AFM) was also used for observation of surface topography. AFM images indicate the homoepitaxially grown diamond (100) surfaces were almost atomically flat surfaces. Hydrogen density of a hydrogen-radical-beam-treated diamond (100) surface was about 3×10 15 atoms/cm 2 and was not varied by oxidation with oxygen radical beam. The hydrogen density is about twice as large as that of the ideal hydrogen-terminated 2×1 surface. Oxygen density of the oxygen-radical-beam-treated surface was about ≤1×10 15 atoms/cm 2. Either hydrogen-radical-beam or deuterium-radical-beam treatments decreased the hydrogen density. The variations of hydrogen and oxygen densities were discussed in terms of surface structures and roughness.

Observation of surface topography using an RBS microbeam

The surface topography of a patterned multilayer specimen was studied by Rutherford backscattering (RBS) analysis using a 2.0 MeV 4He + nuclear microprobe with two detectors set at 100° and 135° scattering angle at opposite sides relative to the beam. A qualitative description of the surface topography was given by RBS tomographic images that could be interpreted taking into account shadowing effects.

Steric and wind‐induced changes in TOPEX/POSEIDON large‐scale sea surface topography observations

Three years of TOPEX/POSEIDON altimeter data are analyzed with respect to large‐scale fluctuations in sea surface height observations and underlying physical processes. In midlatitudes the most conspicuous feature in the large‐scale changes in sea surface height are related to surface buoyancy fluxes, predominantly surface heat fluxes. The next prominent variability on subannual timescales is the adjustment of the ocean to varying winds stress fields in terms of planetary waves. The degree to which basin‐scale sea surface height variations relative to the steric component can be described as a time‐dependent Sverdrup balance is addressed for the Pacific Ocean. If a flat bottom ocean is assumed, a significant correlation of meridional mass transport variations inferred from TOPEX/POSEIDON and a simple Sverdrup model can be found in the Pacific Ocean north of 40°N, but it fails elsewhere. Numerical ocean general circulation models show a good agreement with the TOPEX/POSEIDON observations in all those components of ocean variability and allow further insight into the dynamics that govern observed sea surface height changes.

Oriented thick films grown by cryoelectrophoretic deposition

High- thick films of (YBCO) were grown on Ag substrates by a cryoelectrophoretic technique, i.e. deposited by electrophoresis in a cryogenic environment. The orienting effect is provided by the application of an external magnetic field of small intensity (120 G). After sintering, these films exhibited a superconducting transition at 92 K in the electrical resistivity. Oriented films show significantly enhanced critical current densities. A detailed study of the structural and morphological properties of the film surfaces was undertaken using scanning electron microscopy, x-ray diffraction and scanning force microscopy (SFM). All microscopies revealed different types of film growth induced by the application of an external magnetic field during the cryogenic deposition showing an increasing degree of order with the field intensity (0 - 120 G). Observations of surface topography as studied by SFM are also discussed.

Surface characterization of thin layers of aluminium oxide

Thin oxide layers of commercial pure aluminium (1100-Al) and AlZnMgCu alloy (7075-Al) were characterized after oxidation in a 2.45 GHz microwave discharge in oxygen plasma at low temperature (400 ± 50 °C). The composition and structure of the oxide layers were studied by Auger electron spectroscopy (AES) and Fourier transform IR (FTIR) spectroscopy. In addition, atomic force microscopy (AFM) and micro-indentation techniques were used for surface topography observations and for the evaluation of the coating-surface deformation response. It was found that the 1100-Al layer was composed of duplex sublayers, namely an external γ-Al 2O 3 layer followed by an interdiffused Al-O sublayer. Under similar oxidation conditions the oxide structure of 7075-Al alloy was mainly composed of Mg-O. The surface features largely depended on the plasma processing parameters. The oxide-substrate composite layer was characterized by higher microhardness values up to about twice that of an untreated substrate. The microhardness value was mainly determined by the oxide composition, microstructure and thickness. An indentation dimensional effect (IDE) was evident in the treated sample, and was confirmed by microscale measurements. The chemical and structural characterization of the oxide layers is presented and discussed with emphasis on the role of processing and micro-alloying effects on the fine layer characteristics.

Application of piezoresistive Wheatstone bridge cantilever in advanced atomic force microscopy techniques

The paper presents an application of the Wheatstone piezoresistive bridge in advanced AFM investigations. We have utilized this cantilever in investigations of the contact and noncontact modes, and in investigations of lateral forces and modulation load force microscopy. In the case of non-homogeneous surfaces, investigations of various surface parameters and topography observations are very important. Such surfaces are used in most industrial applications, and investigations of their properties at the nanometre scale is of great interest.

Dislocation Structures and Intergranular Crack Initiation in Fatigued Copper.

Although a number of models for the initiation of intergranular cracks under fatigue have been proposed, most of them are not considered to be sufficient qualitatively. In this study, the mechanism of intergranular crack initiation in fatigued copper is investigated on the basis of the observation of dislocation structures and surface topography by means of transmission and scanning electron microscopy. At the intersections of ladder-like structures with the grain boundary, extrusion-type intergranular deformations are frequently observed. It is also found that the ladder-like structures are sometimes formed along the grain and twin boundaries. On the basis of these observations, a mechanism of crack initiation at the grain boundary is proposed.

Structural and morphological characterization of high quality Y 1Ba 2Cu 3O x epitaxial films by atomic force and high resolution scanning electron microscopies

Epitaxial Y 1Ba 2Cu 3O x (YBCO) films with very smooth surface morphology and excellent superconducting properties ( T c = 92 K, J c = 10 7 A cm −2) were grown on {100} SrTiO 3 and {100} MgO substrates by pulsed laser deposition (PLD). The film surfaces were structurally and morphologically characterized using atomic force microscopy (AFM) and high resolution scanning electron microscopy (HRSEM). Both microscopies revealed different types of film growth and outgrowths which consist of epitaxial and non-epitaxial grains. Some of the outgrowths consisted of high densities of small insulating nanoparticles and, since it appears from HRSEM that they are distributed throughout the interior of the film, they would seem to have high enough densities to become potential candidates for flux pinning sites. The results have also shown that the outgrowths and other surface features formed on the YBCO films are sensitive to composition and deposition conditions. Observations of surface topography as studied by both AFM and HRSEM are discussed in the present paper.

Fatigue Properties and Dislocation Structures of Polycrystalline Copper Film.

Fatigue properties of polycrystalline copper films subjected to pulsating stresses are investigated on the basis of observations of surface topography, fracture surface and dislocation structure. Fatigue limit corresponding to 107 cycles of a rolled copper film is 2. 3 times higher than that of an annealed one, but the fatigue limit ratio of the rolled specimen is lower than that of annealed one. From the observations of the surface crack and fracture surface, it is found that fatigue crack initiation and early-stage crack growth mechanisms of annealed bulk copper are not necessarily applicable to those of film. No striations are formed in both films. In annealed films, cell structures are formed under high-cycle fatigue whereas no band/ladder structures are formed. Dislocation structures near the fatigue crack in annealed films are similar to those of bulk specimens except for the absence of intensely elongated cells observed in the shear flow regions in the bulk specimen. No appreciable change during fatigue was found in the dislocation structures of rolled films.

Application of electron holography to surface topography observation

The principle behind electron holography and its application to surface topography observation are briefly reviewed. A surface displacement field can be quantitatively observed in sub-ångström units as contour fringes in an interference micrograph, using reflection electron holography. Surface steps and dislocations are observed.

Reflection electron holographic observation of surface displacement field

Reflection electron holography was applied to the observation of the surface displacement field induced by a dislocation. The detailed surface topography including the terminating step height was quantitatively observed. The effect of diffraction phase shift on the measurement was estimated based on the columnar approximation with phase calculation by matrix formulation of the dynamical theory. The result shows the diffraction phase shift does not affect the surface topography observation except for the core region of the dislocation.

Dislocation Structures and Grain Boundary Cracking in Low-Cycle Fatigued 70/30 Brass.

The mechanism of grain boundary (GB) crack initiation in low-cycle fatigued 70/30 brass is investigated on the basis of the observation of dislocation structures and surface topography by means of transmission and scanning electron microscopy. The dislocation structures are almost the same as those observed in a high-cycle fatigue test. Although typical dislocation structures are not indicative of strain localized regions (SLRs), the SLRs are recognized in the favorably oriented grains. At the intersections of such SLRs with the GB, extrusion-type GB deformations are frequently observed. These GB deformations are considered to be responsible for GB cracking. Based on the observations, the possible mechanism for the GB cracking in low-cycle fatigued 70/30 brass is discussed.

Satellite altimetry reveals seafloor tectonic fabric

During the 1980s satellite radar altimetry matured as a geophysical technique, quickly becoming the best way to map the gravity field of the world's oceans. Maps derived from SEASAT altimeter observations of sea surface topography (or geoid) revealed much that was previously unknown about the marine gravity field [Haxby, 1987] and underlying seafloor, particularly in the vast areas that are poorly charted by traditional shipboard observations.Seafloor topography, and to a lesser extent, crustal/upper mantle density variations, produce the short wavelength (<200 km) undulations in the marine gravity field. This is simply due to the gravitational attraction of the mass in the seamount or similar structure emplaced on the seafloor. For topographic structures beneath the sea that are 20‐200 km in spatial extent, this attraction causes the gravity anomalies at the sea surface to vary in proportion to the relative height of the underlying structures. (This ignores isostasy or internal deformation of the Earth's crust and mantle, which acts to reduce this gravitational effect particularly over long‐wavelength—greater than 200 km—topography.) The ratio between gravity anomalies and height variations is slightly less than 0.07 milligals per meter (1 mGal equals 10‐5 m/sec2). Therefore, the fine structure in these marine gravity fields reflects the tectonic fabric imprinted in the seafloor. This fabric includes the mid‐ocean ridge axes (where tectonic plates form), fracture zones, which record the directional history of seafloor spreading, seamount chains, rifted continental margins, and other features that chronicle the history of relative motion among the tectonic plates over the past 200 million years.

A point defect model for fatigue crack initiation in Ni 3Al+B single crystals

Transmission electron microscopy of boron-doped Ni 3Al single crystals, oriented for single slip and cyclically deformed at room temperature, revealed a high density of dislocation dipoles and point defect clusters. Observations of circular perfect dislocation loops, Frank loops, vacancy tetrahedra and spherical voids provide evidence of vacancy condensation during fatigue cycling at room temperature. It is suggested that lattice misfit develops between persistent slip bands (PSB) and matrix as a result of the generation and coalescence of excess vacancies in PSBs. The misfit strain at PSB/matrix interfaces is considered to increase with increasing cumulative plastic strain. Together with SEM observations of surface topography, it is suggested that fatigue damage in Ni 3Al single crystals is initiated by the formation of microvoids (microcracks) at PSB/matrix interfaces. The microvoids (microcracks) break down the coherency of the PSB/matrix interfaces and thereby relieve the accumulated misfit strain at the interfaces. A model of fatigue crack initiation based upon a surface energy criterion is proposed.