Six European National Measurement Institutes (NMIs) have joined forces within the European Metrology Research Programme funded project NANOTRACE to develop the next generation of optical interferometers having a target uncertainty of 10 pm. These are needed for NMIs to provide improved traceable dimensional metrology that can be disseminated to the wider nanotechnology community, thereby supporting the growth in nanotechnology. Several approaches were followed in order to develop the interferometers. This paper briefly describes the different interferometers developed by the various partners and presents the results of a comparison of performance of the optical interferometers using an x-ray interferometer to generate traceable reference displacements.

We introduce a novel approach to refractometry using a low coherence interferometer at multiple angles of incidence. We show that for plane parallel samples it is possible to measure their phase refractive index rather than the group index that is usually measured by interferometric methods. This is a significant development because it enables bulk refractive index measurement of scattering and soft samples, not relying on surface measurements that can be prone to error. Our technique is also noncontact and compatible with in situ refractive index measurements. Here, we demonstrate this new technique on a pure silica test piece and a highly scattering resin slab, comparing the results with standard critical angle refractometry.

The National Physical Laboratory, UK, has been active in the field of engineering nanometrology for a number of years. A summary of progress over the last five years is presented in this paper and the following research projects discussed in detail. (1) Development of an infrastructure for the calibration of instruments for measuring areal surface topography, along with the development of areal software measurement standards. This work comprises the use of the optical transfer function and a technique for the simultaneous measurement of topography and the phase change on reflection, allowing composite materials to be measured. (2) Development of a vibrating micro-CMM probe with isotropic probing reaction and the ability to operate in a non-contact mode. (3) A review of x-ray computed tomography and its use in dimensional metrology. (4) The further development of a metrology infrastructure for atomic force microscopy and the development of an instrument for the measurement of the effect of the probe–surface interaction. (5) Traceable measurement of displacement using optical and x-ray interferometry to picometre accuracy. (6) Development of an infrastructure for low-force metrology, including the development of appropriate transfer artefacts.

Two significant figures of merit for optical coherence tomography (OCT) systems are the axial and transverse resolutions.Transverse resolution has been defined using the Rayleigh Criterion or from Gaussian beam optics. The axial resolution is generally defined in terms of the coherence length of a Gaussian shaped source. Whilst these definitions provide a useful mathematical reference they are somewhat abstracted from the three dimensional resolution that is encountered under practical imaging conditions. Therefore, we have developed a three-dimensional resolution target and measurement methodology that can be used to calibrate the three-dimensional resolution of OCT systems.

Current methods to characterise specific properties of polymeric nanocomposites (PNCs), such as particle loading and dispersion profile, rely on a number of techniques that require special sample preparation and treatment, are very expensive, require long measurement times and quite often produce ambiguous results that are difficult to evaluate and interpret. In addition, given their complexity, they are not entirely suited for in-situ industrial environments. This paper presents alternative techniques based on optical diffraction and diffusion mechanisms combined with signal processing that can successfully discriminate between different particle loadings and levels of dispersion. The techniques discussed in this paper are Fourier-domain optical coherence tomography in the infra-red, Fraunhofer wavefront correlation in the visible red and oscillatory photon correlation spectroscopy in the visible green parts of the spectrum. Most importantly, they are non-invasive, are compact, fast and efficient, can potentially analyse large areas of the material and therefore suited for a wide variety of research and industrial situations.