Phase Measurement Interference Microscopy PMIM

25 X 25 pm ) and an interference microscope (b). Copyright for the interference microscope image Schaefer Technologie GmbH, 2004. 

Reprinted with permission. The line scan is a cross-section through the AFM image (white line), denoting the shallowness of the structure. 

The PMIM measurement (Figs 8.16b and 8.17) provides the same local information but in addition allows one to easily obtain an overview over large surface areas of mm. There is no problem wifh adhesion of surface particles on the scanning tip, and height variation in the micrometer range can also be imaged. Of course, since it is an optical far-field method, the lateral resolution 

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While electron or ion beam techniques can only be applied under ultra-high vacuum, optical techniques have no specific requirements concerning sample environment and are generally easier to use. The surface information which can be obtained is, however, quite different and mostly does not contain direct chemical information. While with infra-red attenuated total reflection spectroscopy (IR-ATR) a deep surface area with a typical depth of some micrometers is investigated, other techniques like phase-measurement interference microscopy (PMIM) have, due to interference effects, a much better surface sensitivity. PMIM is a very quick technique for surface roughness and homogeneity inspection with subnanometer resolution. 

In the first part of the chapter several methods used to observe morphology of polymer blends are presented. Various optical microscopic methods are reviewed, including such modem techniques as photon tunneling microscopy (PTM), scanning near-field optical microscopy (SNOM), phase measurement interference microscopy (PMIM), surface plasmon microscopy (SPM) and optical waveguide microscopy (OWM). Many of these methods have been developed to study surfaces and thin films. However, they can also be applied to polymer blend morphology. 

The phase measurement interference microscopy (PMIM) is mainly used for surface analysis. A resolution depth of 0.6 nm can be achieved, whereas the lateral resolution is only in the range of about 1 ftm [White et al., 1990]. A laser beam in the microscope is reflected from the sample surface and simultaneously from a semitransparent smooth reference surface [Stamm, 1992]. The interference pattern is recorded which can be converted into a contour map of the sample surface, e.g., to determine the root-mean-square roughness of materials. 

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