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A scanning probe microscope (SPM) builds an image or map of a surface by moving a very sharp tip across it and recording how the tip interacts with the sample, rather than by focusing light or electrons. It is a family of techniques, with the scanning tunneling microscope (STM) and the atomic force microscope (AFM) as the two best-known members. It is used to measure surface structure and local properties at the nanometre scale.
What is a scanning probe microscope?
The National Laboratory of the Rockies (NLR, formerly NREL) describes SPM as tools that “scan very sharp tips extremely close to (several nanometers) or in contact with the material being analyzed.” The interaction between tip and sample surface is monitored and controlled to generate the output, and the measured interaction can be a force, a current or a capacitance (NLR, Scanning Probe Microscopy, checked 2026-11-07).
That is the key difference from other microscopes: the image is not a magnified view formed by lenses but a map assembled point by point from a measured tip-sample signal. For the optical side of that comparison see the optical microscopy resolution limit.
How do scanning probe microscopes work?
A tip is brought within a few nanometres of the surface, or into contact with it, and scanned across the sample. The instrument records the chosen tip-sample interaction at each position and converts those readings into an image or property map. Which interaction is recorded defines the technique.
The STM, the original instrument of this kind, was introduced at IBM in Zurich in 1981 by Gerd Binnig and Heinrich Rohrer, who received the 1986 Nobel Prize in Physics for it. A fine tungsten tip, one atom wide, scans a few angstroms above the sample; a small current tunnels between tip and surface, and its strength changes with the surface shape, producing a topographic image. IBM’s account says the motivation was that optical microscopes cannot resolve below a wavelength of light while electron microscopes could not reach individual atoms, and that the team spent 27 months refining vibration and noise control. In 1990 Eigler and Schweizer used the technique to arrange xenon atoms to spell “IBM” (IBM History, Scanning Tunneling Microscope, checked 2026-11-07).
What are the main types of scanning probe microscopy?
NLR lists the following techniques in its SPM capability. The table maps each to what it measures, using NLR’s own descriptions.
| Technique | What it measures |
|---|---|
| Atomic force microscopy (AFM) | Nanoscale surface topography |
| Scanning tunneling microscopy (STM) | Tunneling current between tip and surface |
| Conductive AFM (C-AFM) | Conductivity, via voltage between tip and sample |
| Kelvin probe force microscopy (KPFM) | Work function / surface potential |
| Scanning capacitance microscopy (SCM) | Qualitative doping information in semiconductors |
| Scanning spreading resistance microscopy (SSRM) | Resistivity, from conductors to insulators |
| Piezoresponse force microscopy (PFM) | Piezoelectric response |
| Magnetic force microscopy (MFM) | Magnetic structure |
| Contact resonance / force volume | Mechanical properties |
| Scanning electrochemical microscopy (SECM) | Electrochemical reactions |
| Scanning microwave impedance microscopy (SMIM) | Conductance and capacitance |
| Scanning thermal ionic microscopy (STIM) | Ionic motion |
Scanning tunneling microscope
The STM images by tunneling current and is the original SPM. Our guide to scanning tunneling microscopy covers it in depth.
Atomic force microscope
The AFM maps topography and, in its many modes, other local properties. See atomic force microscopy imaging modes compared.
How fine is the resolution?
Resolution depends on the instrument, the technique and the sample, so there is no single figure for “an SPM.” As one worked reference, NLR lists the following for its own instruments. These are one facility’s values, not generic specifications.
| NLR instrument or mode | Listed resolution |
|---|---|
| AFM | <10 nm lateral, <1 nm vertical |
| Omicron UHV STM | 0.1 nm lateral, 0.01 nm vertical |
| KPFM and C-AFM | about 30 nm |
| SSRM | about 40 nm |
| SCM and PFM | about 50 nm |
| MFM | about 100 nm |
NLR also states a maximum field of view of 100 µm on its Bruker systems and 12 µm on the Omicron UHV system. In this facility’s listing, property-mapping modes resolve more coarsely than topography or tunneling imaging.
What are the applications of scanning probe microscopy?
NLR gives these examples from its materials work: atomic terraces and step ledges on gallium phosphide grown on silicon; conductivity at cadmium telluride grain boundaries; resistance at the degraded interface of a silver-grid/silicon solar cell; and measurement of air-sensitive samples in instruments housed in an argon glovebox. The IBM account describes the STM’s first experiment, imaging a gold crystal surface, and its later use to position individual atoms.
Who uses it: IBM describes the STM as an essential tool in disciplines as diverse as semiconductor manufacturing, molecular biology and materials science, and NLR applies SPM to materials and solar-cell research.
How does SPM compare with electron microscopes?
SPM, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are different families: SPM probes a surface with a tip, while SEM and TEM use electron beams. For the electron-beam side, including what SEM is used for, read SEM vs TEM. For a broader view of instrument types, see what a research microscope is and the most powerful microscopes.
Common mistakes
- Treating SPM as one technique with one resolution; the technique and instrument set the figure, as the table above shows.
- Assuming the tip-sample interaction is the same in every mode; each mode measures a different quantity, so results from different modes are not interchangeable.
FAQ
How do scanning probe microscopes work?
A sharp tip is held a few nanometres from, or in contact with, a surface and scanned across it while the instrument records a tip-sample interaction such as force, current or capacitance. The recorded values are assembled into an image or property map.
What would a scanning electron microscope be used for?
SEM is a separate, electron-beam technique rather than a scanning probe method; our SEM vs TEM comparison covers its uses.
What are 10 different types of microscopes?
This page covers the scanning probe family, whose members are listed in the table above. For optical, electron and other instrument classes, see what a research microscope is.
What are the applications of microscopy?
For scanning probe methods, the applications NLR describes are mapping atomic-scale surface steps, conductivity at grain boundaries, interface resistance in solar cells and work on air-sensitive samples; see the applications section above.
Sources
- National Laboratory of the Rockies (formerly NREL), Scanning Probe Microscopy, https://www.nlr.gov/materials-science/scanning-probe-microscopy, checked 2026-11-07.
- IBM History, Scanning Tunneling Microscope, https://www.ibm.com/history/scanning-tunneling-microscope, checked 2026-11-07.
