National Physical Laboratory

Metrological Atomic Force Microscopy (AFM)

Metrological Atomic Force Microscope

The atomic force microscope can be regarded as the window into the nanoworld with applications in imaging, metrology and manipulation. A metrological atomic force microscope can be used to calibrate step height standards with nanometre uncertainty and lateral pitch standards with sub nanometre uncertainty. Traceable measurements of the displacement of the AFM tip with respect to the sample are made using optical interferometry. Currently, a number of new designs for the head for the metrological atomic force microscope are under way to produce a suite of versatile heads that can be used both for calibration of transfer artefacts and measurement of irregular surfaces.

In collaboration with the Czech Metrology Institute, NPL is investigating measurement of the errors associated with high precision scanning stages used both in metrological atomic force microscopes and in general in nanopositioning applications. A suite of algorithms have been developed for the characterization of stages using calibration gratings. This work will be continued within the EMRP project JRP io07 6 DoF: Metrology and movement for positioning in six degrees of freedom. In collaboration with the University of Bristol this work will be extended to high speed atomic force microscopy.

To further reduce the uncertainty of their calibration and that of measurements of non-periodic structures it is important to understand the effect of the interaction between the AFM tip and the sample. Tip-sample interactions can give rise to apparent topographic features which if uncorrected can lead to erroneous dimensional measurements.

Measurements made using an AFM of a UHV prepared silicon (111) surface

An atomic force microscope for studying the effects of tip sample interactions on dimensional measurements has been developed jointly with PTB. The instrument uses fibre interferometry to detect vertical deflection of the cantilever and provide a signal for servo control. An NPL Plane Mirror Differential Optical Interferometer is used for traceable measurement of vertical motion of the cantilever and an additional beam deflection system detects and additional cantilever bending.

One of the first measurements made using the AFM was of a UHV prepared silicon (111) surface. Single monatomic steps (0.314 nm) have been resolved using the differential optical interferometer.


EMRP project MechProNo: the mechanical properties of nanoobjects

NPL is providing the dimensional nanometrology for this EMRP project. Work is in progress to reconstruct the shape of the AFM tip using both established and new software routines with data from the Tip Sample Interaction AFM as well as traceable dimensional measurments of nano objetcs.

For more information, please visit the project website

Currently, new heads for the metrological atomic force microscope are being designed to produce a versatile suite head that can be used both for calibration of transfer artifacts and measurement of irregular surfaces.

Research themes include:

Calibration of transfer standards for atomic force microscopy
Investigation of instrumentation errors associated with atomic force microscopy
Investigation of Tip sample interactions
Combination of atomic force microscopy with x-ray interferometry

Research team

  • Andrew Yacoot
  • Matia Lazzerini
  • Jason O'Neill
  • John Mountford
  • Nigel Cross

Recent publications

Collaborators

For more information, please contact Andrew Yacoot

Last Updated: 4 Nov 2014
Created: 23 Jul 2013

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