tunnelelektronmikroszkóp

The tunnelelektronmikroszkóp, often abbreviated as TEM (Tunneling Electron Microscope), is a powerful microscopy technique used to visualize atomic-scale structures. It operates by exploiting the quantum mechanical phenomenon of electron tunneling. In a TEM, a sharp conductive tip is brought extremely close to a conducting surface, typically within a few angstroms. A small voltage is applied between the tip and the sample. Electrons can then "tunnel" across the vacuum gap from the tip to the sample, or vice versa, depending on the polarity of the applied voltage. This tunneling current is highly sensitive to the distance between the tip and the surface.

The TEM utilizes a feedback loop to maintain a constant tunneling current. As the tip scans across the sample surface, the feedback system adjusts the tip's vertical position to keep the current constant. This adjustment in height is then recorded as a function of the tip's lateral position, creating a topographical map of the surface at atomic resolution. The resolution of a TEM is exceptionally high, often reaching sub-angstrom levels, allowing for the imaging of individual atoms and their arrangements. TEMs require vacuum conditions to prevent scattering of electrons by air molecules and are typically used for imaging conductive samples. Applications include the study of material surfaces, atomic defects, molecular structures, and nanoscale electronic devices.