Cleaning diamond surfaces using boiling acid treatment in a standard laboratory chemical hood

Abstract

Diamond is the basis for numerous applications in optics, electronics, and quantum science due to its desirable material properties and the existence of optically active spins such as the nitrogen-vacancy (NV) center. For some applications, pristine diamond surfaces are required. However, treatments such as irradiation and high-temperature annealing used to create NV centers produce unwanted graphitic and pyrolytic domains of carbon that are difficult to remove using most chemical treatments. A boiling mixture of nitric, perchloric, and sulfuric acids is known to selectively etch graphitic carbon and is commonly used in the research community to restore a clean diamond surface. The risks associated with using these acids, in the presence of organic material, are explosion due to the potential creation of perchlorate salts, as well as ignition due to the presence of an oxygen source from all three acids and a fuel source from the organic material. In this paper, we will discuss a method that mitigates these risks of the cleaning process without requiring a special laboratory chemical hood with a wash-down feature. This method was brought to the attention of health and safety staff after a research group at The University of Pennsylvania requested information about the safety of the procedure and preventative controls.