National Physical Laboratory

Metrological Atomic Force Microscopy (MAFM)

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 is an AFM with traceable metrology, usually optical interferometry that measures the displacement between the AFM tip and the sample. A MAFM can be used to calibrate step height standards with nanometre uncertainty and lateral pitch standards with sub nanometre uncertainty. 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.

Figure 1: Different scan trajectories obtained using routines from the Gwyscan library
Figure 1: Different scan trajectories obtained using
routines from the Gwyscan library

 

 

 

The Czech Metrology Institute (CMI) and NPL have jointly written as series of intelligent scanning routines (Gwyscan) for providing alternative scan trajectories, selective scanning, drift compensation and edge detection in order to increase the versatility of metrological AFMs.

 

 

 

 

We are also 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 is being developed for the characterization of stages using calibration gratings.

Measurements made using an AFM of a UHV prepared silicon (111) surface
Figure 2: Image of silicon atomic stapes;
space between each ring 0.314 nm,
measured traceability with the optical
interferometer on the Tip Sample AFM

 

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.

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. AFM tips were reconstructed using both established and new software routines using traceable data from the Tip Sample Interaction AFM. Dimensional measurements were made of nano objects and effects of tip sample interactions on dimensional measurements were investigated.

For more information, please visit the project website


EMRP project 3D Nano

This European project is developing three dimensional traceable metrology for atomic force microscopy.

For more information, please visit the project website

NPL is developing electron beam deposited and carbon nanotube AFM tips, specifically for dimensional metrology and investigating tip sample interactions using fibre interferometry based detections systems and vector probing. A combined x-ray interferometer AFM facility is also being developed for high resolution pitch measurements.

Research team

  • Andrew Yacoot
  • Herve Dongmo
  • Edward Heaps
  • Andrew Lancaster
  • John Mountford

Recent publications

Collaborators

For more information, please contact Andrew Yacoot

Last Updated: 25 Sep 2017
Created: 25 Sep 2017

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