Optical interferometry, surface

M. Reinstaedtler, U. Rabe, V. Scherer, J.A. Turner, and W. Arnold, Imaging of flexural and torsional resonance modes of atomic force microscopy cantilevers using optical interferometry. Surface Science, (2003) in print... 

The advent of lasers allowed optical interferometry to become a useful and accurate technique to determine surface motion in shocked materials. The two most commonly used interferometric systems are the VISAR (Barker and Hollenbach, 1972) and the Fabry-Perot velocity interferometer (Johnson and Burgess, 1968 Durand et al., 1977). Both systems produce interference fringe shifts which are proportional to the Doppler shift of the laser light reflected from the moving specimen surface. Both can accommodate a speci-... 

Optical interferometry can be used to measure surface features without contact. Light reflected from the surface of interest interferes with light from an optically flat reference surface. Deviations in the fnnge pattern produced by the interference are related to differences in surface height. The interferometer can be moved to quantify the deviations. Lateral resolution is determined by the resolution of the magnification optics. If an imaging array is used, three-dimensional (3D) information can be provided. 

With diblock copolymers, similar behavior is also observed. One component is enriched at the surface and depending on miscibility and composition a surface-induced ordered lamellar structure normal to the surface may be formed. Recent investigations include poly (urethanes) [111], poly(methoxy poly (ethyleneglycol) methacrylate)/PS [112] and PS/PMMA [113, 114]. In particular the last case has been extensively studied by various techniques including XPS, SIMS, NR and optical interferometry. PS is enriched at the surface depending on blockcopolymer composition and temperature. A well ordered lamellar structure normal to the surface is found under favourable conditions. Another example is shown in Fig. 6 where the enrichment of poly(paramethylstyrene), PMS(H), in a thin film of a di-... 

BLM surface tensions have been determined by the application of an ultrasmall hydrostatic pressure to one side of the membrane and measuring the resultant curvature changes by optical interferometry (Fig. 61). Typical values of 0.2-Q.3 mNm 1 were obtained for y for glyceryl monooleate and phosphatidyl-serine BLMs [413]. 

There are various surface techniques, eg., optical interferometry high frequency capacitance and resistance method, which demonstrate the build up of the physically and chemically reacted film during boundary lubrication in scuffing reactions (Anghel et al., 1997 Dowson et al., 1996 Smalley and Cameron, 1996). 

Stein D, Hetherington D, Dugger M, Stout T. Optical interferometry for surface measurement of CMP pads. J Electron Mater 1996 25(10) 1623-1627. 

Su, Y.-D., Chen, S.-J., Yeh, T.-L. (2005) Common-path phase-shift interferometry surface plasmon resonance imaging system. Optics Letter 30 ... 

The fact that each particle enclosed in the primary bulk layer transformed into a craze leaves a mark on the SEM picture of the fracture surface, does not seem surprising. But the fact that only face to face particles are detected by optical interferometry is more striking Fig. 23 shows schematically the proposed explanation. As long as only a single particle is absorbed by the craze, the craze fibril drawing... 

Attempts have been made previously to use the craze shapes recorded by means of optical interferometry to calculate the craze stress distribution . There are at least two problems in the use of craze profiles obtained by interferometry for craze surface stress calculations ... 

The Fourier transform method has been used to calculate the craze surface stress distribution from craze shapes obtained by means of optical interferometry — the craze shapes are the same in air and in toluene gas, only their sizes vary — the craze surface stress is almost constant along the craze boundary — the craze fibril volume fraction remains constant in air and in toluene gas over the whole velocity range, despite the fact that at low velocity in toluene gas the craze length reaches 4 times the length in air — the optical interference setup may give valuable information on the variations of craze fibril volume fraction, but not on its absolute numerical value. 

The above studies have benefited from a fertile exchange with experimental groups using the Surface Force Apparatus (SFA). The SFA allows the mechanical properties of fluid Aims to be studied as a function of thickness over a range from hundreds of nanometers down to contact. The fluid is confined between two atomically flat surfaces. The most commonly used surfaces are mica, but silica, polymers, and mica coated with amorphous carbon, sapphire, or aluminum oxide have also been used. The surfaces are pressed together with a constant normal load, and the separation between them is measured using optical interferometry. The fluid can then be sheared by translating one surface... 

Surface Roughening/Recession. Two approaches to measurement of surface recession were explored. One method applied a classical form of optical interferometry to optically smooth samples of stone in an attempt to measure results after brief exposure of the surfaces to rain this approach was only partially successful and will be only... 

D. Stein, D. Hetherington, M. Dugger, and T. Stout, optical interferometry for surface measurements of CMP pads,. Electronic Mater., 25(10), 1623-1627, 1996. 

Full-field speckle interferometry is similar to holographic interferometry except that the speckles are observed on the specimen surface by illuminating it with laser light or by establishing an optically speckled surface (for example by painting it). 

Compact tension tests on PMMA specimens give a value of 325 J m" for Gic at 23°C, for a crosshead speed of 5 mm min". The critical crack tip opening displacement 8, determined using an optical interferometry technique, is 4.2 m. Calculate the surface stress acting on the craze formed ahead of the crack tip. 

A wide range of techniques can be used to capture the surface roughness of a component using noncontact methods. Some of the more common instruments used to captore topographic data include confocal microscopy, laser triangulation, focus detection, and optical interferometry. A relatively recent branch of microscopy known as scanning probe microscopy (SPM) yields over 20 other instruments which are defined based on what probe-surface interaction they are monitoring. The SPM family is described in more detail elsewhere in this book and will be briefly mentioned in this article. 

Several optical methods, namely UV-visible optical spectroscopy, surface plasmon resonance (SPR) and planar polarisation interferometry (PPI), were exploited in this work for different... 

In this technique, depicted in Fig. 1.4, forces are measured between two partially silvered atomically smooth mica sheets mounted on silica cylinders, which are positioned with their long axes at 90 degrees to each other. The vertical separation between the cylinders is controlled mechanically for coarse control and for fine control using calibrated piezoelectric transducers. One of the cylinders is fixed, and the other is mounted on a cantilever spring of a calibrated spring constant, capable of measuring forces as low as 10 nN. The separation of the partially silvered layers is determined to a resolution of 0.1 nm using optical interferometry. The difference between the piezoelectric translation and surface separation allow... 

The rheology of networks of cross-linked and bundled F-actin has been shown to exhibit exceptional elastic behaviour that reflects the mechanical properties of individual filaments. The local viscoelasticity has been investigated by microrheology techniques using embedded colloidal probe particles and optical interferometry, or magnetic tweezers. The elastic modulus is a strong function of the actin concentration, thus cross-link density. Actin can be cross-linked to form a network coating the surface of a vesicle. The viscoelastic and deformation properties of actin-coated vesicles has also been examined. 

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