Surface Morphology Damage Research Articles

Femtosecond laser-induced damage morphologies of crystalline silicon by sub-threshold pulses

The effect of sub-threshold pulses of circularly polarized Ti:sapphire femtosecond laser system on crystalline (1 0 0) silicon wafer was investigated. Surface damage morphologies were studied by irradiating the test silicon surface with pulses (peak fluence of 0.25 J/cm 2) in succession. These pulses were below the single-pulse surface damage threshold. After the few initial pulses, the observed surface damage morphologies were found to be characterized by a minor phase change region and a major surface damage area at the center, corresponding to the well-known laser-induced periodic surface structure (LIPSS). Further increase in the number of pulses resulted in the formation of new surface morphologies with different features such as ablation, modification, and re-deposited materials. These features were reproducible and more distinguishable at higher number of pulses.

Stress-induced surface damage and grain boundary characteristics of sputtered and electroplated copper thin films

The morphology of the stress-induced surface damage and its relationship with the microstructure in electroplated and sputtered copper thin films is discussed. After annealing at 435 °C for 1 h, two types of surface damage were observed. In some films, grooves along the grain boundaries were formed, whereas in other films, voids at the grain boundary triple junctions were observed. In films of similar thickness, the triple junction voids were deeper than the grain boundary grooves. It was found that the high energy grain boundaries (HEGBs) or their triple junctions are the sites where damages are generated by thermal stress. The area ratio of the HEGBs to the surface area per grain, which is a function of both the grain size ( d) and the film thickness ( h), as well as the fraction of HEGB ( f), determines the morphological equilibrium between the two types of damage. It is suggested that, in general, a microstructural parameter, d/ hf, can be used to predict the damage morphology in Cu films.

Effect of polarization on the surface damage morphology of GaAs single crystal during irradiation with picosecond laser pulses

A comparative study of damage morphology in GaAs induced by s- , p- and linearly polarized laser light (1.064 μm, 35 ps) is presented. For linearly polarized light damage initiates in the form of pits. This material damage occurs below the surface. For s- or p-polarized light material damage involves only the surface layer. For larger fluences or number of pulses the differences are less marked and the damage morphology occurs in a similar manner either for linearly polarized or s- or p-polarized light. Ripples are formed when multiple irradiation is used due to interference between the front and back faces of the test sample. The spacing of these ripples is 3 μm , which is in good accordance with the reported work of Guosheng et al. (Phys. Rev. B 26 (1982) 5366).

Surface nanostructuring and damage morphologies along 2 GeV gold-ion-implanted tracks

Abstract Good-quality melt-textured YBa2Cu3O7-x materials with Y2BaCuO5 non-superconducting inclusions were irradiated with 2GeV gold ions in order to produce a surface layer with columnar defects. The finaL goal is to gain a basie understanding of the role of the surface columnar defects in determining those magnetic properties of the materials that are related to the vortex confinement. The particie energy and the sample thickness were chosen in such a way that the percentage of irradiated volume is about 10%. In the paper the intrinsic structure and the damage morphology were analysed by means of transmission electron microscopy studies in both cross-section and plan-view geometry. As a result, the columnar defect density, size and shape were obtained. The irradiation produces parallel heavily damaged tracks whose diameter is between 3 and 6nm. The overlapping of some columnar defects was highlighted and had to be taken into account to understand the superconducting properties of irradiated samples. Th...

Surface nanostructuring and damage morphologies along 2GeV gold-ion-implanted tracks

Abstract Good-quality melt-textured YBa2Cu3O7-x materials with Y2BaCuO5 non-superconducting inclusions were irradiated with 2GeV gold ions in order to produce a surface layer with columnar defects. The finaL goal is to gain a basie understanding of the role of the surface columnar defects in determining those magnetic properties of the materials that are related to the vortex confinement. The particie energy and the sample thickness were chosen in such a way that the percentage of irradiated volume is about 10%. In the paper the intrinsic structure and the damage morphology were analysed by means of transmission electron microscopy studies in both cross-section and plan-view geometry. As a result, the columnar defect density, size and shape were obtained. The irradiation produces parallel heavily damaged tracks whose diameter is between 3 and 6nm. The overlapping of some columnar defects was highlighted and had to be taken into account to understand the superconducting properties of irradiated samples. The defects affect an implanted layer of about 50 um. The measured thickness coincides, within the experimental errors, with the thickness calculated by means of the Monte Carlo TRIM simulations.

Influence of particle fracture in the high-stress and low-stress abrasive wear of steel

High- and low-stress abrasive wear tests have been carried out against steel and rubber wheels, with mild steel specimens and silica sand abrasive particles 125–150 and 425–500 μm in size. The effects of particle shape and applied load on wear rate, surface damage morphology and the extent of particle fracture were studied. Fracture of the abrasive particles occurred over a wide range of test conditions and had a marked effect on the wear process. The extent of fracture correlated with the magnitude of the wear rate, and when particle fracture was extensive, it masked the influence of initial particle shape. Under most test conditions, the mechanism of material removal involved multiple plastic indentation by abrasive particles rolling through the contact region.

Laser-stimulated desorption and damage at polished CaF2 surfaces irradiated with 532 nm laser light

Laser-stimulated emission of Ca neutrals from polished CaF2 (111)-surfaces was studied with a quadrupole mass filter system under UHV conditions. For intensity dependent measurements performed at various spots of the crystal surface a threshold pulse energy could be determined where a sharp decrease in transmitted light intensity occurred. Only for a few measurements this threshold coincided with the ablation threshold (type 1 spots). In most cases, however, the transmission breakdown threshold was found to be distinctly lower than the ablation threshold (type 2 spots). For type 2 spots a weak emission of delayed calcium atoms was observed at the transmission breakdown threshold. Irradiated spots have been examined by optical and scanning electron microscopy. Damage phenomena observed included coloration, cracking along crystal axes, surface erosion and surface melting depending on incident laser intensity. Pronounced differences between type 1 and type 2 spots with respect to laser light entrance and exit surface damage morphology were found.

Microstructure of Silicon Nitride Ceramics and Morphology of Surface Damage Induced by Round Indenter

Microstructure of Silicon Nitride Ceramics and Morphology of Surface Damage Induced by Round Indenter

An analysis of adhesive properties of brittle coatings

In a previous study [1] a pendular scratching test was used to perform single-tip abrasion under controlled conditions on massive samples. During operation a pendulum swung down and an abrasive tip, which was fixed radially to this rigid pendulum, scratched a horizontal specimen at the bottom of the trajectory. The length 2L and the maximum depth D of the arc-shaped groove produced could be varied by adjusting the radial position of the tip. A transition scratching depth D* from ductile to brittle abrasion was then defined: this transition depth was found to be correlated to the ratio Kc/H, where K c is the toughness and H the hardness. The relationship was similar to that obtained in static indentation [2, 3] and the transition depth D* was found to fit the relationship D* = ( Kc/H) 15 The incident velocity of the abrasive tip was 2 m s -1 . These scratching tests were run with half-conical indentors (apex angle 90°). The flat surface was in front of the indentor, at a right angle to the scratching direction during experiments. Scratching tests are also commonly used for testing the adhesive properties of brittle coatings [4, 5]. The applied load is increased until brittle chipping occurs, the phenomenon appears similar to that obtained on massive samples and described above. This critical load of brittle chipping is sometimes used to characterize the adhesive proper- ties of coatings. Pendular experiments were conducted in order to analyse the process of scratching of semibrittle coatings and to discern the effects of the brittleness (ratio H/Kc) from effects of the adhesive proper- ties. Tests were run with the same half-conical indentors described above and,with conical inden- tors, apex angle 90 °. The incident velocity of the abrasive tip was 2ms -I. The energy consumed during abrasion was given by the loss of potential energy of the pendulum. A particular material was used in order to observe easily the different effects: aluminium (99.9% pure) coated with commercial unsaturated polyester (UP) resin. Samples were prepared in order to obtain good or poor adhesion of the coating. The thickness of the coating was e = 0.05 ram. Tests were also run on massive samples of aluminium and polyester. A typical morphology of the surface damage is shown in Fig. 1. When the indentor scratches only the coating, a first critical depth D1 is observed. This depth D1 characterizes the onset of lateral cracking of the coating and corresponds to the transition

On Corrosion Fatigue Mechanisms for S45C and SCM435 Steels in Rotating Bending

Morphology of surface damage and small cracks by the corrosion fatigue was studied for quenched and tempered carbon steel S45C and Cr-Mo steel SCM435 in a deionized water and 3%NaCl water environments under rotating bending at frequencies from 0.03 to 30 Hz. In saline water the fatigue strength of the two steels decreased monotonously with increasing number of cycles and testing time, while in the pure water a kind of temporal fatigue limit was observed for frequencies higher than 3 Hz. In the latter case fatigue crack was arrested by the closure effect of corrosion product for certain periods but this was diminished by dissolution after enough long test duration. A map of corrosion fatigue fracture mechanism was proposed based on the results of observation and analysis.

The Morphology of Surface Damage Caused by Friction

An effort is made to functionally connect the morphology of a surface damaged by friction with the sequence of events leading to the damage. The connection between a destructive situation and the resulting morphology is established. The reverse connection, i.e., the use of the morphology as a diagnostic tool, is not complete, mainly because some of the characteristics suggestive of the mechanisms are erased. Still, for cases of one friction pass, e.g., on a spiral track friction machine, the reverse connection is also established.

Closure to “Discussion of ‘The Morphology of Surface Damage Caused by Friction’” (1982, ASME J. Lubr. Technol., 104, p. 581)

Closure to “Discussion of ‘The Morphology of Surface Damage Caused by Friction’” (1982, ASME J. Lubr. Technol., 104, p. 581)

Laser Induced Surface Damage

A summary of recent investigations of surface damage of transparent dielectrics is presented. Damage threshold measurements made on Owens-Illinois ED-2 laser glass at normal incidence and at Brewster's angle are reported. For 30-nsec pulses at normal incidence, exit surface damage thresholds are typically 100 J/cm(2) for ED-2 glass. The observed ratio between entrance and exit damage thresholds for the two geometries can be explained by considering the electric field strengths at the surfaces and including interference between incident and reflected light waves. A similar analysis is applied to surface damage that occurs during total internal reflection. Finally the morphology of surface damage of ED-2 laser glass is described, and a model based upon reflections from the laser induced plasma is proposed to explain the observations.