Optical methods are of choice in a huge number of applications. In particular, those instruments based on vertical scanning methods provide extremely fast, non-contact characterization of surface topography. However some limitations are present. Among them, maximum detectable slope is limited (generally <30°). Local loss of signal, resulting from this limited detection, originates data files containing void pixels, which eventually provide poor surface characterization. This work presents an original approach to overcome instrumental limitation on the maximum detectable slope. The method presented here is based on a software tool that processes images taken with controlled tilt, and returns a high-quality 3D profile of the sample being investigated. Experimental evidence is given with reference to the case of a Vickers indentation on steel.

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Scanning tunneling microscopy heads having some tip-displacement measurement capability are essential for quantitative and accurate measurements. A scanning tunneling microscopy head based on a bimorph parallelogram scanner with a metallized glass cube situated above the tunneling tip is described; The cube acts as a counterelectrode or as a minor for capacitance-based and interferometric measurements of scanner displacements. The capacitive sensors are mounted on differential screws facing the cube in such a way that the lateral Abbe error in the measurement of actual tip-displacements is minimized. The sensor electronics uses a Howland-type alternating current source, and has a deviation from linearity of less than 0.15% up to 30 mu m and a low frequency bandwidth of 1 kHz. (C) 1996 American Vacuum Society

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