Answer to Question #94386 in Quantum Mechanics for prashanth

Question

why you need a conducting sample to study in STM?

Answer 1

STM is the Scanning Tunelling Microscopy. It is a method of getting images of relief of materials' conductive surfaces at high resolution like 0.2 nm. The method works like this: a very sharp needle is approached to a sample. If there is a potential on the needle, a tunelling current 1 to 1000 pA flows through the needle. The sample acquires tunneling voltage. The magnitude of the tunelling current depends on the distance between the needle and the surface of the sample, therefore, one can use that dependency to build the map of heights or topography along the direction of needle's motion That is why the sample should conduct electricity. However, a Scanning Probe Microscope can be used to study non-conducting materials.