Atomic-resolution microscopy in water.

The scanning tunneling microscope is revolutionizing the study of surfaces. In ultra-high vacuum it is capable not only of imaging individual atoms but also of determining energy states on an atom-by-atom basis. It is now possible to operate this instrument in water. Aqueous optical microscopy is confined to a lateral resolution limit of about 2000 angstroms, and aqueous x-ray microscopy has yielded a lateral resolution of 75 angstroms. With a scanning tunneling microscope, an image of a graphite surface immersed in deionized water was obtained with features less than 3 angstroms apart clearly resolved. Further, an image measured in saline solution demonstrated that the instrument can be operated under conditions useful for many biological samples.