Atomic Force Microscopy Techniques in Titanium Dioxide Surface Science

Atomic force microscopy (AFM) has become an indispensable tool for unravelling the atomic-scale structure and functionality of titanium dioxide (TiO₂) surfaces. The oxide exists in polymorphic forms—most notably anatase and rutile—each presenting distinct surface terminations, reconstructions and defect landscapes that govern photocatalytic, electronic and sensing performance. Through modes such as contact, non-contact and dynamic force spectroscopy, AFM affords sub-nanometre resolution of topography, enabling direct visualisation of surface atoms, step edges and vacancy sites. When combined with tunnelling current measurements in hybrid AFM–STM approaches, it is possible to assign elemental species on wide band-gap surfaces. Kelvin probe force microscopy (KPFM) further quantifies local variations in work function and surface dipoles, illuminating how point defects and adsorbates modulate reactivity. Progress in tip functionalisation and high-speed imaging has extended AFM capabilities to dynamic processes such as adsorbate migration and surface reconstruction under realistic environments. These advances bridge fundamental surface science with practical insights for TiO₂-based catalysis, energy conversion and sensor design on a global scale.

Research from Nature Portfolio

Dynamic AFM–STM experiments on the anatase (101) surface have demonstrated simultaneous atomic-resolution imaging and species identification within the oxide’s band gap. By correlating force-distance spectra with tunnelling currents and first-principles simulations, researchers distinguished titanium and oxygen atoms and pinpointed common defect centres. This work established a protocol for unambiguous assignment of surface sites, paving the way for studies of dopant adsorption and molecular adsorption relevant to catalysis and photovoltaics.

Seminal studies of the anatase TiO₂(001)-(1×4) reconstructed surface revealed two intrinsic point defects, identifying the reduced Ti³⁺ site as the primary locus of chemical activity. High-resolution imaging combined with spectroscopic mapping and density functional theory highlighted that only reduced defect sites participate in surface oxidation and reduction reactions. This finding resolved long-standing debates on the reactivity of reconstructed anatase facets and underscored the central role of defect engineering in oxide catalysis.

Atomic Force Microscopy Techniques in Titanium Dioxide Surface Science publication trend

The graph below shows the total number of articles in atomic force microscopy techniques in titanium dioxide surface science across all publications each year (not limited to Nature Index journals).

Technical terms

Atomic force microscopy (AFM): A scanning probe technique that measures forces between a sharp tip and a surface to generate high‐resolution topographic images.

Non-contact AFM (NC-AFM): An AFM mode where the tip oscillates above the surface without making mechanical contact, enabling imaging of soft or reactive surfaces.

Kelvin probe force microscopy (KPFM): A variant of AFM that maps local surface potential or work function by detecting electrostatic forces between tip and sample.

Scanning tunnelling microscopy (STM): A probe technique that records tunnelling current between a conductive tip and a surface, used for atomic‐scale electronic characterisation.

Anatase and rutile: Two crystalline polymorphs of TiO₂, each with distinct lattice structures, surface terminations and reactivity.

Point defect: A vacancy or extra atom located at a lattice site on or beneath the surface, often serving as active centres for adsorption and catalysis.

References

1. Atomic species identification at the (101) anatase surface by simultaneous scanning tunnelling and atomic force microscopy. Nature Communications (2015).
2. Role of point defects on the reactivity of reconstructed anatase titanium dioxide (001) surface. Nature Communications (2013).
3. Subsurface Charge Repulsion of Adsorbed H‑Adatoms on TiO2(110). The Journal of Physical Chemistry C (2014).
4. Imaging the surface potential at the steps on the rutile TiO2(110) surface by Kelvin probe force microscopy. Beilstein Journal of Nanotechnology (2019).