Home – Home – Jornals – Avtometriya 2010 number 4

The precision of measurements performed by atomic-force microscopy (AFM) and highresolution electron microscopy (HREM) for solving problems of metrology and diagnostics of solid nanostructures is discussed. The HREM-measured height of a monatomic step on a Si(111) surface covered by a thin natural oxide film is demonstrated to be 0.314 ± 0.001 nm. The same accuracy is ensured by AFM measurements through controlling the Si surface relief with heating in ultra-high vacuum on specially created test objects with the distance between the steps being approximately 2 μm. It is shown that the geometric phase method can be used to quantify the strains in the crystal lattice of strained heterostructures on the basis of HREM images with accuracy to 10⁻⁴ %, and in situ irradiation by electrons in HREM measurements can be used to visualize ordered clusterization of vacancies and self-interstitial atoms in {113} planes in Si samples.

In this paper we will provide an overview of methods and instruments developed and applied at the National Metrology Institute of Germany (Physikalisch Technische Bundesanstalt - PTB) for high-precision dimensional (linear and angular) measurements and discuss some challenges  for future developments in this important area of metrology.

The paper describes traceable nanometrology based on a nanopositioning machine with integrated nanoprobes. The operation of a high-precision long-range three-dimensional nanopositioning and nanomeasuring machine (NMM-1) having a resolution of 0.1 nm over the positioning and measuring range of 25 × 25 × 5 mm is explained. Various developed probe systems have been integrated into the NMM-1 machine, including a focus sensor, a white light sensor, and tactile nanoprobes. Single-beam, double-beam, and triple-beam interferometers are installed into the NMM-1 machine to measure and control the six degrees of freedom. Measured results are presented.

This review concerns the design and use of micro- and nanosensors based on electrochemical, acoustic, piezoelectric, and optical principles for medical diagnosis and care and for biological research. The target measurands include an ever-increasing number of simple and complex molecules, physical quantities, and electrical and magnetic phenomena.

Optical metrology provides a unique approach to measuring surfaces, both technical and optical, over a wide measurement range from macro to nano. We present two new approaches to measuring aspheric lenses with increased flexibility. The first is based on a modified Twyman -Green interferometer where multiple sources for the illumination of the aspheric surface with different angles are adopted to achieve a local compensation of the gradient and consequently a reduction of interference fringes. The second is based on a chromatic Fizeau interferometer with a diffractive element as null-optic for the measurement of extreme ultraviolet aspheres.

High precision contact scanning probes for measuring miniature components on micro- and nano-coordinate measuring machines requires sensitive mechanisms. This paper analyzes the mechanism of a developed contact probe in order to find its optimal dimensions. The contact probe is composed of a fiber stylus with a ball tip, a mechanism with a wire-suspended floating plate, and focus sensors. The wires experience elastic deformation when a contact force is applied. The probe mechanism with a four-wire floating plate is studied. Stiffness analysis is carried out using the theory of elasticity. It is found that, with a proper stylus length, a contact probe with uniform stiffness can be designed.

Two types of fiber-optical measurement systems are compared: a line with a large number of point sensors based on fiber Bragg gratings (FBGs) interrogated by a tunable continuous fiber laser and a distributed system based on optical time-domain reflectometry (OTDR) of the Raman scattering of radiation of a pulsed fiber laser. Methods for increasing the measurement accuracy with the use of additional calibration of the Bragg wavelength shift over a fiber interferometer in the FBG system and spectral filtration of the Stokes and anti-Stokes components of the Raman scattering with the use of spectral-selective fiber couplers in the OTDR system are proposed and implemented. Physical effects on system parameters are analyzed, compared, and optimized for applications with monitoring of the temperature distribution in turbogenerators and oil wells.

Using a microbolometer detector array, we recorded real-time images of metallic and dielectric objects illuminated by monochromatic terahertz radiation, including those hidden behind an opaque barrier. It is shown that the characteristics of movement of rough objects dynamic can be retrieved from the dynamics of the speckle structure of their images in the terahertz range. An automatic processing algorithm for terahertz videos with recording of moving objects was developed and software implemented.

The limits of applicability of geometrical optical methods of calculating diffractive optical elements for terahertz radiation are determined. Use of the method of hot pressing in vacuum chambers to produce polymer transmissive diffractive elements for controlling terahertz radiation is considered. The effect of radiation absorption on the focal spot size and the radiation resistance of the elements are estimated. Experimental study of the optical characteristics of diffraction lenses fabricated in polypropylene revealed 17 percent differences from the diffraction limit.

A likelihood function is obtained for estimating parameters of weak optical signals during detecting by means of recording emission moments of each photoelectron. Likelihood equations are derived and solved by an example of optimal estimates of a Gaussian pulse. Expressions for compatible and incompatible estimates of all three unknown parameters of the pulse are obtained. Analytical expressions for the Kramer-Rao bounds determining the quality of the estimates obtained are also derived. The variances of compatible estimates of the signal amplitude are demonstrated to be three times those of incompatible estimates, while the variances of the estimates of all parameters are inversely proportional to the product of the signal amplitude and its duration.

Thin films obtained by centrifugation of blood serum of healthy people and people with viscera diseases are studied by methods of spectral ellipsometry and infrared spectroscopy. Physical properties of such films are found to depend on the bio-organic composition of blood serum, which, in turn, is determined by pathological processes proceeding in the human organism. It is of interest that spectral ellipsometry and infrared spectroscopy are suitable nondestructive express methods of screening, i.e., preliminary blood diagnostics for patients with viscera pathology. Ellipsometric data on specific features of formation of bio-organic coatings from blood serum of patients with diffuse pathology of liver, hyperlipidemia, and diabetes mellitus are validated by changes in the fine structure of infrared spectra.

Optoelectronic methods for controlling the appearance of nuclear reactor fuel pellets are considered. In the proposed methods, reflected images of pellet surfaces are taken by digital cameras, which provides high contrast of defective areas against the frame background. Image processing algorithms for identification of defective products are given. An experimental model of a system with a capacity of up to 10 pellets per second was designed. A database containing surface images of simulators and real pellets was designed to train the system. Results of real time processing of the obtained images show that the probability of detection of defective pellets is not less than 95%.