AFM study reveals unknown facts about alumina surface

The non-contact form of Atomic Force Microscopy(AFM) led by researchers from Vienna University of Technology(TU Wien) and University of Vienna has revealed unknown facts about the notably complex structure found on the surface of aluminium oxide.

The research report states that the structure of the crystal on the surface differs from the atoms inside the material at hand, which pursue a stringent arrangement elevating the crystal's characteristic shapes.

Professors Jan Balajka and Ulrike Diebold, among others, used a stiff qPlus force sensor-based nc-AFM method to reveal the precise atomic sequence of the α- Al2O3 exterior.

The researchers uncovered that the rearranged surface allows the aluminium atoms to lance into the material and form chemical bonds with the oxygen atoms in the underlying portion.

This reshuffling of the initial couple of atomic layers immensely reduces the energy, relatively stabilising the structure. Contrary to earlier hypotheses, the numerical proportion of aluminium to oxygen particles remains intact, maintaining the quantitative relationships between the amounts of reactants and products in a chemical reaction.

"In an ncAFM image, one can see the location of atoms, but not their chemical identity," discloses Johanna Hütner, TU Wien. "We overcame the lack of chemical sensitivity by precisely controlling the tip. Attaching a single oxygen atom to the tip apex allowed us to distinguish between oxygen and aluminium atoms on the surface... Mapping the local repulsion or attraction enabled us to visualize the chemical identity of each surface atom directly."

The 3D model of the Al2O3 surface was virtually retrieved with machine learning methods.