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Scanning microscopes, including the scanning electron microscope, tunneling microscope, and atomic force microscope, use a probe or electron beam to scan a sample surface and produce measurable data to create atomic-level images. Scanning electron microscopes detect signals from the interaction of the electron beam with atoms on the surface of the sample, while tunneling microscopes and atomic force microscopes use a conductive tip to produce higher resolution images. Cantilever deflection is measured using a laser in atomic force microscopes.
There are different types of scanning microscopes including scanning electron microscope, tunneling microscope, and atomic force microscope. Typically, scanning microscopes consist of a probe or electron beam that scans the surface of a sample. The interaction between the scanning microscope and the sample produces measurable data, such as current variation, probe deflection or secondary electron production. This data is used to create an image of the sample surface at the atomic level.
The scanning electron microscope is one of several types of scanning microscopes used to image a specimen. The microscope detects the signals resulting from the interaction of its electron beam with the atoms on the surface of the sample. Several types of signals are usually produced including light, X-rays, and electrons.
There are several types of electrons that can be measured by this microscope, including transmitted electrons, backscattered electrons, and secondary electrons. Typically, scanning electron microscopes have a detector of secondary electrons, which are displaced electrons produced by a primary source of radiation, namely the electron beam. Secondary electrons give information about the physical structure of the surface at the atomic level. Typically, the microscope views an area of 1-5 nanometers.
Scanning microscopes that use a probe, such as the tunneling microscope, produce higher resolution images than the scanning electron microscope. The tunneling microscope has a conductive tip placed very close to the sample. A voltage difference between the conductive tip and the sample causes electrons to flow from the sample to the tip.
When electrons cross, a tunneling current is formed and measured. As the conductive tip is moved, the current changes, reflecting differences in height or density on the sample surface. With this data, an image of the surface at the atomic level is built.
The atomic force microscope is another scanning microscope equipped with a probe. It consists of a cantilever and a sharp point that is placed close to the sample surface. As the tip approaches the sample, the forces between the tip and the sample cause the cantilever to deflect. Typically the forces include the mechanical contact force, the van der Waals force and the electrostatic force.
Typically, cantilever deflection is measured using a laser focused on the top surface of the cantilever. Deflection reveals the physical shape of the surface at a particular point. Both the sample and the probe are moved to scan the entire surface. An image is constructed from data obtained from the laser.
