tunnelingmicroscoop

Tunnelingmicroscoop is a term that is sometimes used to refer to a tunneling microscope, a class of scanning probe instruments that image surfaces at near-atomic resolution by measuring quantum tunneling current between a sharp tip and a sample as the tip scans the surface.

Principle: A conductive tip is brought very close to a conductive or semiconductive sample, and a bias voltage drives electrons across the vacuum gap. The tunneling current is highly sensitive to tip–surface distance, decreasing exponentially with separation. Feedback maintains a constant current and records the tip position to produce a topographic map; varying the bias yields spectra related to the local electronic structure (scanning tunneling spectroscopy).

Construction and operation: Typical tips are made of tungsten or platinum-iridium, shaped by electrochemical etching. The instrument is operated in ultra-high vacuum or cryogenic environments to improve stability and resolution, with sophisticated vibration isolation and low-noise electronics. The tip-sample distance is measured in angstroms, and imaging can occur at room temperature or lower, depending on the system.

Applications and limitations: The technique is especially powerful for conductive surfaces and thin films, enabling atomic-scale imaging, surface-state measurements, and manipulation of individual atoms. It requires clean, well-prepared surfaces and may be less effective on insulating materials unless combined with other modes or conductive coatings. The term tunnelingmicroscoop is not standard in English-language literature; most references use scanning tunneling microscope.

See also: Scanning tunneling microscope, Scanning tunneling spectroscopy, Atomic force microscope.