Measurements are presented of the electrical double layer and van der Waals forces between the (0001) surfaces of two single-crystal sapphire platelets immersed in an aqueous solution of NaCl at pH values from 6.7 to 11. The results fit the standard Deryaguin-Landau-Verwey-Overbeek (DLVO) theory, with a Hamaker constant of 6.7 × 10−20 J. These are the first measurements made using the Israelachvili surface forces apparatus without mica as a substrate material, and they demonstrate the possibility of using this technique to explore the surface chemistry of a wider range of materials.

Imaging ellipsometry (IE) combines spatial resolution of optical microscopy with thin‐film measurement capabilities of ellipsometry. It has gained significant interest in recent years and is been used for a wide range of applications from biotechnology to semiconductor metrology. Traditionally, IE is used either as a qualitative technique – not unlike polarized microscopy or Surface Plasmon Resonance (SPR) – with “ellipsometry images” showing surface topology variation, or as a quasi‐quantitative technique where the change in “ellipsometry images” is used to deduce the change in film thickness. In this paper we give a brief critical review of different measurement systems configurations from the point of view of their fitness to quantitative IE measurement. We discuss the methods of calibration and correction that enable to achieve a truly quantitative IE measurement. We show that a fast and reliable quantitative IE can be practically implemented. It is consistent and can be used in lieu of a classical single point ellipsometry in many applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Numerical calculations using the multilayer matrix method show that the interference fringes in the visible spectrum of light transmitted through two back-silvered transparent sheets separated by a dielectric film is greatly modified when a thin metal layer is present on each sheet surface. The layers cause a modulation of fringe intensity and a shift in fringe wavelength which depend on the refractive index and thickness of the layer. Fringes will be well resolved for <40 nm layers of metals with high reflectivity and low absorption. In regard to the use of this interferometer to determine surface separations in the Israelachvili surface forces apparatus, Israelachvili's equation is found to be no longer valid, and a multilayer matrix method is presented. Some unsymmetrical interferometers are also considered.

A novel design for the magnet system of a watt balance is presented. While primarily intended for the watt balance being developed by MSL, this design could be used for other watt balances. It has a radial magnetic field in an annular gap that is screened from external fields. The magnetic field is generated by a single ring-shaped permanent magnet and the geometry is such that the field induced in the permanent magnet by the current in the coil in the weighing mode is zero on average. Hence the magnetic field in the gap is expected to be the same for both the weighing and dynamic modes of a watt balance. From finite element modelling, the magnetic field strength can be uniform to within 40 parts in 10 6 over more than 50 mm (50% of the gap height) and the usable working range for the coil is about 40 mm. Further, the diameter of the annular gap can be relatively small, allowing the coil and its support structure to be kept relatively stiff and light.

A general approach to comparisons in the presence of temporal drift is presented and comparison sequences are discussed for linear, quadratic and cubic drift. Circular comparison sequences of the form (ab. . ), and (ab. . ),a are proposed (where a, b, . . are different items, such as masses, and n is a repeat factor) with the best performance achieved when three to five items are involved in the comparison. A matrix least squares model is used to obtain information about the drift, the item differences and their uncertainties. The emphasis of the paper is on mass comparisons, where the dominant drift is in the balance zero, but the approach is applicable to comparisons generally and its application to gain drift is also presented.