A low-temperature ultrahigh vacuum atomic force microscope for biological applications

We present an atomic force microscope ~AFM! for operation at low temperatures under ultrahigh vacuum conditions. It uses the laser beam deflection method to measure the bending of the cantilever. The four quadrant photodiode allows the detection of vertical and lateral forces. The AFM has been developed for studying biological samples. Images of deoxyribonucleic acid plasmids have been obtained in contact mode.