Unravelling microscopic properties of the (2x1) surface reconstruction of calcite(104)

• Applicant: Dr. Philipp Rahe
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2016 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 289665220

It is well-known that crystal surfaces can behave in very complex ways when formed by cleaving, cutting, or other processing. A textbook example of such a behaviour is the (111) surface of silicon, which undergoes a complex structure transition to a (7×7) reconstruction upon forming. Building upon the large body of work of studying metal and semiconductor surfaces, there is currently increasingly strong interest in investigating wide-bandgap insulator materials. Among these materials, calcium carbonate (CaCO3) is not only one of the most ubiquitous minerals in nature, but especially its most stable polymorph calcite is the principal constituent of most limestones and is of highest relevance in numerous applications including agricultural soil treatment, pharmaceuticals, construction materials, or optical devices to name a few. Accordingly, the most stable cleavage plane of a calcite crystal, the (104) surface, has intensively been studied over the last decades by a number of methods including low energy electron diffraction, X-ray photoelectron spectroscopy, molecular modelling, or atomic force microscopy. Some of the experimental studies suggest the existence of a (2×1) surface reconstruction, however, the driving force and microscopic geometry of this reconstruction is still poorly understood, rendering the surface model to be still incomplete. The ultimate goal of this project is to unravel microscopic details of the (2×1) reconstruction on calcite(104) and to identify the basis of its formation. A detailed investigation by high-resolution non-contact atomic force microscopy (NC-AFM) with functionalised tips at 5 K is planned. In particular, the project work includes studying the deposition of different species on calcite(104) to investigate the response of the surface on the adsorbed material. High-resolution imaging will be performed and used to aim for a determination of the atomic structure of the reconstructed surface.

• DFG Programme: Independent Junior Research Groups