Petr Klapetek, Virpi Korpelainen and Jyrki Räisänen.
The public examination of the doctoral dissertation ”Traceability for nanometre scale measurements. Atomic force microscopes in dimensional nanometrology” by Virpi Korpelainen (senior research scientist at MIKES) took place at the University of Helsinki in November 26, 2014. Petr Klapetek from the Czech Metrology Institute acted as the opponent.
Reliability of measurement is a crucial element in research and industry and metrological traceability to the SI units guarantees commensurate units. In this thesis, a traceability chain is established for nanometre scale measurements. To achieve this, a metrological atomic force microscope (MAFM) was developed for accurate measurements and calibration of transfer standards and a laser diffractometer for calibration of 1-D and 2-D gratings. In these methods, traceability to the SI-metre was guaranteed by using lasers whose vacuum wavelengths were calibrated. Moreover, calibration methods for commercial AFMs were established.
Laser interferometry is widely used in length measurements. However, there exists a small nonlinearity in sub-fringe measurements. A method to correct this nonlinearity was developed. In addition, accurate length measurements by laser interferometry require precise knowledge of the index of refraction of air. An acoustic method was developed for determining the effective refractive index of air in the whole beam path in a laser interferometer.
Characterization of instruments, validation of methods and uncertainty estimations are a crucial part of traceability. Therefore, thorough uncertainty estimates based on the characterization of the instruments are given for all measurements in this thesis.
Comparisons between laboratories are the best way to ensure commensurate measurements. International comparison results between national metrology institutes for pitch and step height transfer standards are listed.
Additional information: Senior research scientist, Virpi Korpelainen,
+358 2950 54412