Final answer:
Atomic force microscopy (AFM) is least similar to transmission electron microscopy (TEM) as AFM operates by measuring probe height variations with constant current, while TEM images specimens by transmitting electrons through them in a vacuum.
Step-by-step explanation:
Atomic force microscopy (AFM) is a type of scanning probe microscopy that is distinct from both scanning tunneling microscopy (STM) and transmission electron microscopy (TEM) in several ways. While STM measures variations in current at a constant height to form images of surfaces at the atomic level, AFM maintains a constant current and measures the probe tip's height variations.
In contrast to the AFM and STM, the TEM works differently by using a focused electron beam transmitted through a thin specimen to create an image, often requiring the sample to be in a vacuum and allowing for viewing of internal structures at atomic resolution.