Overcoming Challenges in Atom Probe Tomography of Carbonate Minerals: Application of <i>In Situ</i> Chromium Coatings for Improved Experiment Yield

Carbonate minerals such as calcite cover a significant portion of Earth's ice-free land surface. Beyond their widespread distribution, they play a critical role in geological processes, including the global carbon cycle and various biogeochemical processes. Understanding the crystal chemistry of carbonates is therefore essential for advancing our knowledge of these systems. Atom probe tomography offers promising potential for revealing nanoscale chemical and isotopic processes in minerals; however, its application to carbonates remains technically challenging due to their poor thermal conductivity and absorption. In this study, we apply and adapt an in situ metallic coating technique and optimize atom probe tomography acquisition parameters for calcite. The results demonstrate that applying a Cr coating to calcite specimens significantly improves experimental yield and enhances mass resolution during atom probe analysis. Despite these improvements, the data do not yield stoichiometric proportions for calcite due to the post-ionization dissociation of CxOy molecules into neutrals. These findings provide a framework for extending atom probe tomography methods to other poorly conducting or beam-sensitive materials.