Table of contents

In the Yoshida Nano-Mechanism Project, two types of nanometrology have been studied: microtopography measurement with the scanning tunnelling microscope (STM) and distance measurement with the laser interferometer. Using the STM, graphite surfaces and biological samples were examined and a modification of the STM instrumentation, the capacitor insertion method, usefully improved performance. A unique two-wavelength method has been studied to eliminate air-turbulence-induced errors in the laser interferometer. Measurement technology is closely related to control technology through the need for feedback position sensors. Control technology, in turn, creates new possibilities for measurement technology. Position control to one nanometre has now been achieved.

The Physikalisch-Technische Bundesanstalt (PTB) is engaged in a range of projects which call for dimensional precision of order 1 nm. These include research and development (i) to improve linear and angular displacement metrology; (ii) to investigate the physical interaction of high resolution probes with technical surfaces and microstructures and so to represent the microtopography, form and dimension of measures. The limits vary with application and technology. Currently, only one-dimensional displacement measurements and microtopography provide the level of accuracy for which figures in the sub-nanometre range can be given. For the measurement of form and dimension of volumetric standards, barriers have still to be recognized around 10 nm. The application of single-crystal silicon devices for different length and angle measurements with nanometre and nanorad accuracy is of particular interest for the PTB.

The measurement of nanometre displacements with picometre resolution has been made possible by a phase-modulation recovery scheme applied to an optical Michelson interferometer using polarization encoding. In contrast to conventional schemes, phase modulation is carried out before the interferometer optics. In this way, the low-frequency components of the phase shift between the two interfering beams are locked at zero (within limits set only by shot noise) before beam splitting by a feedback loop driving the modulator. An interferometer prototype, illuminated by a beam thus modulated, was constructed and coupled to an X-ray interferometer to compare the optical and X-ray interferometric measurement values of sub-nanometre displacements. A resolution better than 1 pm over a 100 Hz bandwidth was obtained.

An ultra micro-indentation system for investigating the elastic and plastic properties of surface coatings and near-surface materials is described. The instrument produces minute indentations by the application of loads to geometrically accurate pointed or spherical diamond indenters. Material properties are derived from records of the load and depth of penetration. Depth of penetration is measured with a resolution less than 1 nm. The force at initial contact can be substantially less than 0,1 mN. The instrument has a wide range of research and quality control applications which include the determination of the depth distribution of hardness and elastic modulus of hard and soft materials – TiN, gold and polymer films and coatings, for example. It also has applications in the determination of the workhardening index, in fracture mechanics and in exploring the material properties of small areas of individual phases in polyphased materials.

A theoretical framework for mapping the performance of measuring instruments has been developed that is used to interpret the results of measurements at the nanometric level, where it is particularly important to understand the geometrical and physical interactions between the measuring instrument and the object being measured. Nanometric topographic measuring instruments that have been developed at the NPL span measuring ranges of 0,01 nm to 3 nm in surface amplitude and 0,3 nm to 100 nm in surface wavelength.

Precision measurements at the National Research Laboratory of Metrology used to determine fundamental constants and to test physical theory are described: they are related to the determination of silicon lattice spacing; the magnetic flux quantum; and a search for the fifth force. Equipment and techniques for nanometrology are described in terms of the nanoscale, nanoguide and nanodrive, all of which have immediate applications in advanced technology. An example is introduced which demonstrates the power of the scanning tunnelling microscope (STM) in nanometrology.

Procedures for precision polishing and testing spheres of silicon and silica are described. Hand-polishing procedures result in the production of spheres of 90 mm diameter with deviations from roundness of less than 50 nm. The roundness was measured to an uncertainty of 5 nm on a Talyrond with averaging procedures to account for spindle errors.