Measurements Of Step Height Research Articles

Optimization of interference fringe tuning by improving the sensitivity of measurements of the phase step height

The condition for obtaining optimal tuning of interference fringes, which correspond to their perpendicular direction to the phase step interface, are considered. Optimal tuning is attained when the sensitivity of measurements increases due to the overlap of a pair of holographic interferograms. It is noted that this method can be implemented most easily when a copy of the first interferogram rotated relative to the interface of the phase step is used as the second interferogram.

An Atomic Force Microscopy study of the growth of calcite in the presence of sodium sulfate

In situ atomic force microscopy (AFM) has been used to compare the growth of pure calcite and the growth of calcite in the presence of sulfate ions from aqueous solutions at a constant value of supersaturation (S.I. = 0.89) with respect to calcite. The effect of sulfate ions on calcite growth rates is determined and a potential incorporation of sulfate ions is identified in the calcite during growth. Solutions supersaturated with respect to calcite with solution concentration ratio of one and a constant pH of 10.2, were prepared and sulfate was added as Na 2SO 4 aqueous solution. The solution composition was readjusted in order to keep the supersaturation and pH constant. PHREEQC was used to determine relevant solution concentrations . In situ AFM experiments of calcite growth were performed using a fluid cell and flowing solutions passed over a freshly cleaved calcite surface. Growth rates were determined from the closure of the rhombohedral etch pits induced by initial dissolution with pure water. The spreading rate of 2-dimensional nuclei was also measured. At low concentrations of sulfate (≤ 0.5 mM), no effect on the growth rate of the calcite was observed. At higher concentrations (2 to 3 mM) of sulfate, the growth rate increased, possibly because a higher concentration of calcium and carbonate was necessary to maintain the supersaturation constant. At much higher concentrations of additional sulfate (up to 60 mM) the growth rate of the calcite was substantially decreased, despite the fact that a further increase of calcium and carbonate was required. The morphology of 2-dimensional growth nuclei became increasingly elongated with increasing sulfate content. Measurements of step height showed that newly grown steps were approximately 1 Å higher when grown in high sulfate concentrations, compared to steps grown in sulfate-free solutions. At sulfate concentrations above 5 mM the growth mechanism changes from layer growth to surface roughening. These observations suggest that the new growth has incorporated sulfate into the calcite surface.

Comparison on step height measurements in the nano and micrometre range by scanning force microscopes

The ability to make traceable measurements of step height is vital for the worldwide nanotechnology community. In contrast to the former CCL-S2 so-called NANO2 comparison, this Euromet comparison focuses only on measurements made using scanning force microscopes (SFM).The Czech Metrology Institute (CMI), CNR Istituto di Metrologia G Colonnetti (IMGC), Swiss Federal Office of Metrology and Accreditation (METAS) and Physikalisch-Technische Bundesanstalt (PTB – Pilot laboratory) agreed to participate in this comparison using their SFM to measure the step height on three standards with nominal values of 40 nm, 1000 nm and 2000 nm. The reference value for each standard was calculated using the weighted mean of all measurements that fulfilled the En ⩽ 1 criteria.Most of the results were in a good agreement with the reference values except for one instrument which failed to measure the largest step height. This shows first that SFM are able to measure step heights up to 2000 nm with very small uncertainty, and secondly, that each instrument has to be very carefully examined before it can be used on a daily basis to provide calibrations for industry and science.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the EUROMET, according to theprovisions of the CIPM Mutual Recognition Arrangement (MRA).

Traceable calibration of transfer standards for scanning probe microscopy

A Metrological Atomic Force Microscope (MAFM) has been constructed for the traceable calibration of transfer standards for scanning probe microscopy. It uses optical interferometry to generate image scales with direct traceability to the national standard of length. Three interferometers monitor the relative displacements of the AFM tip and sample in the x, y and z directions and the interferometer data is used directly to construct 3D images of sample surfaces. Traceable dimensional measurement of surface features may then be derived from the image data. This paper describes the MAFM instrument and presents a measurement uncertainty budget. Examples are given of measurements of pitch and step height on calibration transfer standards for scanning probe microscopy.

International comparison of surface-texture parameters organized by the Asia-Pacific Metrology Programme

This paper reports on an international comparison of surface-texture parameters, Ra, Ry5 and Ry, carried out between nine national metrology institutes from 1996 to 1998 under the auspices of the Asia-Pacific Metrology Programme (APMP) and coordinated by the CSIRO National Measurement Laboratory (NML, Australia). The results show that the consistency of the Ra measurements is generally better than that of the Ry5 and Ry measurements, which appear to split into two sub-groups with some crossover. Agreement is somewhat better for artefacts of higher surface roughness. Measurements of step height were also made as a potential indicator of correlation between the basic length scale and the surface-roughness parameters. These show satisfactory agreement, within the stated uncertainties and with the normalized error, En, values < 1 in all cases.

Developments in Australia's surface roughness measurement system

Roughness standards in Australia are established, maintained and disseminated by the Melbourne Branch of the National Measurement Laboratory (NML), Commonwealth Scientific and Industrial Research Organisation (CSIRO). A Taylor Hobson Talysurf 3 stylus instrument has been upgraded by replacement of the original valve amplification with solid-state electronics and the implementation of Windows 95 based software for profile analysis. The amplification is calibrated using gauge blocks wrung onto an optical flat or with master groove standards, calibrated using an interference microscope with a helium–neon laser light source. Measurements of step height or peak-to-valley roughness height in the range 0.1–50 μm are possible. The stylus instrument interfaces directly with a PC via a high speed analogue-to-digital card. Software has been developed to analyse grooves and steps and to characterise surfaces by calculation of various parameters such as arithmetic mean deviation ( R a). Typical uncertainties are better than 4% at a confidence level of 95% and are calculated automatically by the software according to the ISO “ Guide to the Expression of Uncertainty in Measurement”. Technical and administrative procedures are discussed in the context of accreditation within the National Association of Testing Authorities, the Australian laboratory accreditation organisation. The facility has participated informally in a regional Asia–Pacific Metrology Programme intercomparison in which three surface roughness and two groove standards were circulated and the results are discussed. Using historical data, alternate traceability routes, and various artefact chains, the integrity of surface texture measurement at the new facility has been evaluated and verified.

Characterization of biomolecule immobilization by scanning force microscopy using a wet‐masking technique

AbstractThe assemblage of molecular layers was investigated using scanning force microscopy (SFM). A wet‐masking technique was used for the preparation of monolayer steps by partial masking of the substrate with an elastomeric mask during incubation in the modification buffers. The subsequent adsorption of biotin, streptavidin, and biotiny lated beads onto a gold substrate was investigated by SFM visualization of the created steps. The molecular layers were characterized based on measurements of step height and surface roughness. The simultaneous visualization of the surface before and after modification minimizes artifacts introduced by changes in tip shape or imaging parameters.