Shallow Scratches Research Articles

Plasmon-Mediated Scattering of Light by Ion Eroded Ag(110) Surfaces

Enhanced scattering of laser light from polished and ion bombarded Ag(110) surfaces is reported. Ar+ ions with energy 500 eV were directed against the sample at angles of incidence between 30° and 45°. The ion current was about 4–6 μA. The experiments were made with a diode pumped solid-state green laser that emitted at 532 nm, with a continuous wave power output around 5 mW. In a controlled series of experiments a sudden increase in scattered intensity could be observed at a fluence of about 2 × 1017 ions/cm2. The scatterograms showed radially oriented intensity streaks, superimposed on a diffuse and isotropic background intensity. No correlations with low-index crystallographic directions were found. The surface structure was studied by means of optical interferometry and atomic force microscopy. The scattered light was found to be dominated by the contribution from shallow surface indentations and scratches remaining from the polishing process. It is demonstrated that the sputtering creates a surface topography with correlation length of a few μm. A mechanism based on surface plasmons is proposed to be responsible for the observed increase in scattered intensity.

Scratching resistance of diamond-like carbon coatings in the subnanometer regime

In order to examine the scratching resistance of ultrathin hydrogenated amorphous carbon (a-C:H) coatings used in magnetic storage devices, a large number of scratches with reproducible residual groove depths well below 1 nm has been examined. All measurements were carried out with an atomic force microscope and diamond-tipped cantilevers. The analysis of such shallow scratches is made possible by means of an image processing procedure which minimizes surface roughness effects using subtraction imaging. This method was applied to a series of sputter-deposited, fully aged, unlubricated amorphous coatings with different hydrogenations. For low hydrogen content in the sputtering gas, the scratching resistance decreased with an increasing amount of hydrogen, in accordance with many other experiments. In contrast, an unusual slight improvement of the scratching resistance for a further increase of hydrogenation was obtained.

Material Removal Mechanism of Magnetic Fluid Grinding of Ceramic Balls.

In order to clarify the material removal mechanism of advanced ceramic balls in magnetic fluid grinding, balls of PSZ, Al2O3 and two types of Si3N4 were finished by magnetic fluid grinding. For PSZ and two types of Si2N4, removal rate was inversely proportional to hardness Hv, and shallow scratches were observed on the polished surface. Thus, plastic deformation is considered as dominating material removal mechanism for PSZ and two types of Si2N4 materials. For Al2O3, pits due to detachement of grains were observed on the polished surface. Thus, the dominating material removal mechanism of Al2O3 is considered as inter granular fracture.

A new etchant to reveal the subsurface damage on polished gallium arsenide substrates

In the present investigations, a new etchant, viz., Bi(NO 3) 3H 2O 2HCI (“BNCL etchant”) has been established for GaAs to reveal the subsurface damage induced during the polishing procedures. The investigated (1 0 0) oriented, silicon-doped n-type GaAs and undoped semi-insulating GaAs wafers were polished with slurries having pH 8 and 9. After etching, the shallow scratches are visible in addition to the wave-like defects. The etching rate was 6.5 μm/min for n-type and 8 μm/min for semi-insulating. When the etching was carried out for 2 min, all the observed damage vanished and most of the surface of both (n-type and semi-insulating) samples were found to be uniformly etched. The capability of the etchant to reveal the subsurface damage has been confirmed.

Atomic force microscopy studies of rubbed polyimide surfaces used for liquid crystal alignment

Liquid crystal (LC) surface alignment, which controls off-state contrast in LC displays, is commonly achieved by directional rubbing of polyimide-coated substrates. In order to better understand the alignment mechanism we have used tapping-mode atomic force microscopy to study the dependence of polymer surface morphology on rubbing conditions. Based on results from three polyimides rubbed at different strengths with two cloths, we have identified five surface feature types induced by the rubbing: (1) isolated point defects, (2) occasional deep scratches (≥5 nm), (3) numerous very shallow scratches (mostly ≤1 nm deep), (4) nanoscale surface islands (3–10 nm high, number density ≳109 cm−2), and (5) modified background texture. The last feature confirms that the entire surface has been affected by the rubbing process. The finest resolution achieved, about 10 nm full width, was insufficient to resolve individual polymer chains. Of the features observed, only occasional very deep off-axis scratches clearly affected azimuthal LC alignment. Quasiperiodic features observed under weak rubbing conditions suggest that initial rubbing occurs by a stick-slip mechanism, and the widths of such features gives an estimate of fiber-surface contact size.

The role of counterface imperfections in the wear of polyethylene

Ultrahigh molecular weight polyethylene (UHMWPE) acetabular cups of total replacement hip joints tend to wear more quickly in vivo than indicated by most laboratory wear tests. The reason for this discrepancy has been attributed to the generation of fine scratches on the surfaces of the stainless steel femoral heads in service. In the present paper an account is given of an investigation of the influence of single imposed imperfections in stainless steel counterfaces upon the wear of UHMWPE wear pins in linear reciprocating wear tests. The imperfections were in the form of either transverse or longitudinal scratches or single indentations, all generated by diamond markers. It has been found that a single transverse scratch can increase the wear rate of the polymer to a remarkable extent; the major factor being the piled-up steel along the edge of the scratch. When the piled-up material was removed by remedial lapping the wear rate returned to its initial value corresponding to the isotropic roughness of the undisturbed counterface. Longitudinal scratches yielded a less marked yet recognizable increase in the wear rate of the polyethylene. Single diamond indentations did not generate piled-up edges of steel and had little effect upon the wear rate of the polymer. The findings demonstrate the severe effect which simple imperfections on a hard counterface can have upon the wear of polymers. Even shallow transverse scratches can increase the wear rate by an order of magnitude. Remedial lapping of the scratched counterfaces, to remove the piled-up material, largely restores the low wear characteristics of the unblemished counterfaces. The study supports the views offered previously in explanation of the difference between in vivo and laboratory wear rates of total replacement hip joints.

Microstructure and Lattice Defects in Polycrystalline Nuclear Ceramics

Transmission electron microscopy of several nuclear ceramics has been extended to thin sections of as - fabricated poly-crystalline materials, by use of a thinning technique utilizing only common metallographic practices. The method is based on work by Doherty and Leombruno. However, while mechanical thinning (polishing) produces large, evenly thinned specimens, the surface of ceramic materials retains many shallow scratches and defects introduced by the polishing medium. On the other hand, the chemical thinning methods commonly applied produce only very small areas which are thin enough for examination by transmission electron microscopy, since preferential attack occurs on grain boundaries, inclusions, second phases, etc. By combining the chemical polish with the mechanical thinning procedures, large, relatively clean areas of ceramic materials can be produced. Another significant advantage is that in the course of thinning, the same specimens can be examined frequently and in detail by light microscopy, some physical measurements can be made along the way (e.g., microhardness, spectral transmission, autoradiography), and all observations can be closely correlated finally with the high resolution electron microscopy.

PRODUCTS and PROCESSES: PROVIDING INDUSTRY WITH THE MEANS TO COMBAT CORROSION

Aluminium Satin Etch Solution An immersion etching solution, Noralbryte, is said to be capable of removing or obliterating dielines and similar draw marks, shallow scratches and similar damage from the surface of extruded metal and rolled sheet. It is also possible to remove superficial shallow corrosion damage from such surfaces. As the process gives a smooth satin gloss finish, it is particularly suited as a pretreatment prior to anodising. The full processing sequence affords a very high protective finish for such parts as window frames, curtain walling, shop fronts, etc., as well as parts made from sheet and strip.

Religious Documents from Roman Cyprus

Provenance unknown. Now in the Cyprus Museum, but with no record of acquisition. A rectangular sandstone block, both stone and inscription virtually complete. H. from 0·175 m. to 0·18 m.; w., 0·464 m.; th., 0·115 m. The surface, save for three long but shallow scratches, good. The alphabet is debased classical, notable forms being Ε and Η with the central stroke disconnected, Ρ with its top approximately rectangular. Letters, from 0·01 m. to 0·017 m. Squeeze. (Fig. 1.)From its lettering this inscription is in all probability earlier than the reign of Hadrian and should belong to the second half of the first century. Tryphon and Philon are both names common along the south coast of Cyprus; but as an indication of provenance this fact must be used with great reserve.The worship of Nemesis in Cyprus is not otherwise known to me, though Tyche with whom she is here identified occurs both at Chytri and at Paphos. An inscription tells of a dedication to the Fortune of Chytri under Philometor; another of how a certain Apollonia and her husband Patrocles were honoured, perhaps under Hadrian, as the founders of a Τυχαῖον and as the priests of the Fortune of the Metropolis Paphos. Here we do not find this limited conception of Tyche: the present inscription is an excellent and it seems an early illustration of the worship of Nemesis as a universal goddess, identified on the one hand with Justice, on the other with Fortune. In the theological and philosophic speculation of the second and third centuries these ideas are commonplaces. I am not aware that they have as yet occurred in the first.