Resurrecting dirty atomic force microscopy calibration standards

Cleanliness of atomic force microscopy samples before imaging has always posed questions for users. The same is true for height calibration standards. In this shop note, the authors discuss using $CO2$ snow cleaning as a way to clean heavily contaminated standards and show its effectiveness in removing contamination. Further, they show that the cleaning does not damage the surface, nor alter the step heights, and can lead to improved imaging.