Low-temperature noncontact atomic-force microscope with quick sample and cantilever exchange mechanism

We present the design and performance of a noncontact atomic-force microscope (AFM) operating at low temperatures (LTNCAFM). For the first time, a “top bath” cryostat is used to avoid long-distance translation of the AFM unit, while protecting the fragile optical fiber, and to reduce outgassing. The top bath cryostat is optimized by using three radiation shields with two shutters. The AFM unit is cooled down to 5 K for 14 h with 4.6 l liquid helium. The quick sample and cantilever exchange is performed even at low temperatures. The optimal positioning of the optical fiber with respect to a cantilever can be performed with a three-dimensional micropositioner within 10 min. The high performance of the LTNCAFM is demonstrated with an atomically resolved image of a Si(111)7×7 surface.