Scanning Probe Microscopy (SPM): AFM, STM, MFM and Technique Selection

Scanning probe microscopy (SPM) is a family of surface-measurement techniques in which a sharp probe scans across a sample while a feedback system records a local interaction. SPM includes atomic force microscopy (AFM), scanning tunneling microscopy (STM), magnetic force microscopy (MFM), electrical and surface-potential modes, and other specialized methods. The right technique depends on the property you need to measure and the sample environment.

How scanning probe microscopy works

• A sharp tip or sensor is positioned close to the sample.

• A piezoelectric scanner moves the probe or sample in a raster pattern.

• The instrument measures a local interaction such as force, tunneling current, magnetic force gradient, electrical response, or surface potential.

• Feedback maintains a setpoint or records changes while x and y are scanned.

• Software constructs images and correlated signal channels from the position and detector data.

SPM images are measurement maps rather than optical photographs. Tip shape, feedback settings, scan speed, drift, vibration, sample roughness, and the selected interaction all influence the result.

Main SPM techniques

Atomic force microscopy (AFM)

AFM measures tip–sample forces and can image conductive or insulating materials. Contact, dynamic/tapping, and non-contact operation address different surface and sample-mechanics requirements. AFM is commonly used for topography, roughness, nanomechanics, and force measurements.

Scanning tunneling microscopy (STM)

STM measures quantum tunneling current and generally requires a conductive or semiconductive sample and tip. It supports constant-current, constant-height, and spectroscopy measurements.

Read the comprehensive scanning tunneling microscopy guide.

Magnetic force microscopy (MFM)

MFM uses a magnetically sensitive probe to map magnetic force gradients above a surface. Lift height, tip magnetization, topographic cross-talk, sample coercivity, and magnetic field environment are important.

Electrical and functional modes

• EFM maps electrostatic force or force gradient.

• KPFM maps contact-potential difference with mode- and calibration-dependent interpretation.

• Conductive AFM and SSRM measure local current or resistance with a conductive probe and controlled contact.

• PFM measures electromechanical response and requires careful control of electrostatic and mechanical artifacts.

• Scanning Hall probe microscopy measures local magnetic field using a Hall sensor rather than a cantilever force interaction.

Which SPM method should you choose?

• Choose AFM for surface topography on conductive or insulating samples.

• Choose STM for conductive surfaces when tunneling-current imaging or local spectroscopy is required.

• Choose MFM or scanning Hall probe microscopy for magnetic contrast or field mapping.

• Choose KPFM or EFM for surface-potential or electrostatic measurements.

• Choose conductive AFM or SSRM for local electrical transport or resistance contrast.

• Choose a low-temperature or field-compatible platform when the phenomenon depends on temperature or magnetic field.

Common instrument components

• Probe or sensor and exchangeable holder.

• Fine XYZ scanner and coarse approach or positioning stage.

• Interaction detector: optical lever, interferometer, tunneling-current amplifier, Hall sensor, or another transducer.

• Feedback controller, data acquisition, and scan software.

• Optical microscope or camera for navigation where needed.

• Vibration isolation, acoustic shielding, and environmental control.

Sample and data-quality requirements

• Match sample conductivity, roughness, size, mounting, and environment to the chosen mode.

• Use a probe whose coating, stiffness, resonance, apex, and geometry fit the measurement.

• Control contamination, loose particles, humidity, condensation, grounding, and sample motion.

• Select scan range and z travel at the operating temperature and environment.

• Repeat scans with changed direction, size, speed, setpoint, or probe when checking artifacts.

• Treat apparent lateral feature size cautiously because tip geometry broadens structures.

Ambient and low-temperature product paths

The current hpAFM page lists a broad configuration-dependent mode set including contact and dynamic AFM, non-contact AFM, liquid AFM, MFM, EFM, STM, KPFM, PFM, conductive AFM/SSRM, electrochemical AFM, nanomechanical imaging, and nanoindentation.

View hpAFM.

The ezAFM+ page lists interchangeable 40 × 40 × 4 µm and 120 × 120 × 40 µm scan-head options, alignment-free cantilever mounting, optional liquid operation, and configuration-dependent magnetic and electrical modes.

View ezAFM+.

For conductive-surface STM imaging and spectroscopy, view ezSTM.

For cryogenic and high-field AFM/MFM, view LT-AFM/MFM and the low-temperature AFM guide.

Read the low-temperature AFM selection guide.

Applications

• Surface roughness and nanoscale morphology.

• Thin films, semiconductors, polymers, ceramics, composites, and two-dimensional materials.

• Magnetic domains and local magnetic field studies.

• Local electrical, surface-potential, electromechanical, and nanomechanical characterization.

• Biological or soft materials with suitable probes and environments.

• Nanofabrication, manipulation, and correlative microscopy in specialized systems.

SPM limitations

• Serial scanning is slower than wide-field imaging.

• Tip geometry and condition affect every image.

• Feedback, vibration, drift, contamination, and environmental instability produce artifacts.

• A mode name alone does not guarantee quantitative measurement; calibration and models are required.

• No single SPM configuration supports every mode, sample, temperature, field, liquid, or optical integration.

Frequently asked questions

Is AFM the same as SPM?

AFM is one type of SPM. SPM is the broader family that also includes STM, MFM and many electrical, magnetic, thermal, and mechanical variants.

Can SPM image insulating samples?

AFM and several force-based modes can. STM normally requires a conductive path.

What determines SPM resolution?

Probe geometry, interaction physics, scanner and detector noise, feedback bandwidth, vibration, drift, sample stability, and data-processing choices all matter.

Does SPM measure only topography?

No. Depending on the mode, it can map magnetic, electrical, mechanical, electromechanical, thermal, chemical, or spectroscopic response.

Discuss your SPM application

Send the sample material, dimensions, roughness, conductivity, property of interest, scan range, required environment, temperature or field, and integration needs. An NMI engineer can recommend the appropriate SPM platform and quotation.