Microscopy, SPM and AFM

Queensgate AFM & SFM microscopy applications

Atomic Force Microscopy (AFM) or Scanning Force Microscopy (SFM) is a type of scanning probe microscopy (SPM) which scans a surface with a mechanical probe achieving resolutions of fractions of a nanometer.

AFMs can be used to measure the forces between the probe and the sample as a function of their mutual separation, producing a high resolution, three-dimensional topographical image of the sample surface. This is achieved by raster scanning the position of the sample with respect to the tip and recording the height of the probe that corresponds to a constant probe-sample interaction.  The surface topography is commonly displayed as a pseudocolour plot.

In manipulation, the forces between tip and sample can also be used to change the properties of the sample. Examples of this include atomic manipulation, scanning probe lithography and local stimulation of cells.

Mechanical properties like stiffness, adhesion strength and electrical properties such as conductivity or surface potential can also be measured.

Sub-nanometer spacial resolution in AFM scanners

High performance piezoelectric stages are used in the specimen scanner of an AFM to provide sub-nanometer spacial resolution.

The stages are used to provide a three dimensional, X, Y and Z profile of the surface of the sample. The dynamic performance and accuracy of the Z stage is important as it adjusts to the topography of the sample. A fast response allows the x and y stage to scan quickly across the surface of the sample reducing drift due to the effect of temperature changes and increasing throughput.

We provide high precision, high-speed piezo actuators and flexure driven stages using capacitive positioning sensors for use in ‘close loop AFM’. Our engineers pioneered the use of capacitive sensors in high performance stages and actuators with the highest resolution and linearity of movement. 

With options for travel ranges of 50, 100, 200um; the XY stages provide market leading positioning resolution; the 100um range provides resolution better than 0.25nm.

Finite element analysis of the flexure guidance mechanisms has reduced parasitic angular motions providing the smoothest, most repeatable scan with greatly minimized out-of-plane motion.

Decoupling the Z axis by using a separately mounted Z stage will usually provide the best dynamic performance and range. For example the NPS-X-25 operates over a closed loop range of 25um, with a sub-nanometer resolution of better than 0.1nm and resonant frequency of 6KHz.

Find out more about our Nanopositioning Stages