Phase-shifting Interference Microscope Research Articles

Spectrally resolved phase-shifting interferometry of transparent thin films: sensitivity of thickness measurements

Spectrally resolved white-light phase-shifting interference microscopy can be used for rapid and accurate measurements of the thickness profile of transparent thin-film layers deposited upon patterned structures exhibiting steps and discontinuities. We examine the sensitivity of this technique and show that it depends on the thickness of the thin-film layer as well as its refractive index. The results of this analysis are also valid for any other method based on measurements of the spectral phase such as wavelength scanning or white-light interferometry.

Spectrally resolved white–light phase–shifting interference microscopy for thickness–profile measurements of transparent thin film layers on patterned substrates

We describe how spectrally-resolved white-light phase-shifting interference microscopy with a windowed 8-step algorithm can be used for rapid and accurate measurements of the thickness profile of transparent thin film layers with a wide range of thicknesses deposited upon patterned structures exhibiting steps and discontinuities. An advantage of this technique is that it can be implemented with readily available hardware.

Phase shift interference microscope study of dissolution-precipitation processes of nonhydrostatically stressed halite crystals in solution

Halite single crystals in saturated solution were used to study dissolution precipitation creep (DPC) at conditions where plastic deformation is negligible. Specifically, the free unloaded surfaces of these crystals were investigated by a novel Linnik-based phase shift interference microscope. The method allows observations of the crystal surface in-situ and with an axial resolution in the nanometer scale. Transport phenomena in open systems, temperature gradients, and gradients in strain energy density were found to cause morphological changes on the free crystal surface by dissolution/reprecipitation. We did not find evidence for DPC by applying a homogeneous stress field to the crystal as long as plastic deformation was avoided. These findings suggest that deformation of rocks by DPC in situations where dislocation creep is not activated, but is rather promoted by fluid transport through the rock or by episodic changes of extensive parameters affecting solubility than by homogeneous stress alone.

Phase-shifting Fizeau interference microscope with a wavelength-shifted laser diode

A phase-measuring Fizeau interference microscopy with a laser diode (LD) source is studied that is based on a phase-shifting method using wavelengths varied stepwise by changing the current in the LD. The effect of the multiple-beam interference fringes on three kinds of phase-extraction algorithms is theoretically and numerically investigated. The phase error due to multiple reflections has a periodicity to one-fourth of the fringe spacing and a four-stepping method has the smallest error among interesting algorithms. The measurement error with a four-stepping method can be minimized by averaging two sets of measurements with an initial phase difference of π/4. This eases the adjustment of an initial phase by a tunable LD. A phase error caused by the power change in the LD is eliminated by normalizing the captured interferograms. Experimental results are presented with a Fizeau interferometer to show the usefulness of such procedures.

Phase-shift interference microscope employing a simple method to depress speckle noises for the thickness measurement of thin films

Phase-shift interference microscope employing a simple method to depress speckle noises for the thickness measurement of thin films

Phase-shift interference microscope for the investigation of dipole-orientation distributions

A compact experimental setup for an electro-optical microscope is introduced. The microscope is based on phase-shift interferometry (a well-known tool for surface profilometry) that is modified for measuring electrooptic responses. Its feasibility is demonstrated with a two-dimensional map of the electro-optic activity of a periodically poled nonlinear-optical side-chain polymer.

Calibration of step height standards for nanometrology using interference microscopy and stylus profilometry

Calibration of step heights standards used for the vertical calibration of such topography measuring instruments as styli, atomic force microscopes, and tunneling microscopes is described in this article. The calibration uncertainty of a commercial high-resolution contact stylus instrument is compared with the calibration uncertainty of two types of interference microscopes. One of them is a phase-shifting Mirau interference microscope, the other is a Linnik interference microscope. The fringe pattern of the latter can be evaluated visually using an Abbe comparator, and automatically using the spatial carrier fringe-pattern analysis. The calibration uncertainties of the mechanical and optical instruments were investigated. Measurements were performed with very smooth rectangular-shaped groove standards with depths from 3 μm to 60 nm. The estimated and experimental uncertainties were compared.

Effect of surface conformity on friction

The usefulness of microtribological theories depends on their application to interfaces of a larger scale. Contact conditions over a large area, however, are not uniform but are a consequence of the geometry of each interface as well as the deformation of the supporting materials on either side of the interface. As a result, surfaces which have statistically uniform topography on the microscale may still exhibit non-uniform sliding friction behavior. In this study, we measure periodic friction force variation during slow speed sliding of a ceramic slider on a lubricated, carbon-overcoated aluminum disk. Using a phase-shifting interference microscope, we measure the geometry of the entire sliding track. Together with the slider geometry, this information can be used to characterize the surface conformity of the sliding interface at every point along the track. We calculate a “conformity index” and correlate it to the friction.