SEMs work by focusing a beam of electrons onto a sample. The electron beam is generated by an electron gun, which is located at the top of the microscope. The beam is then accelerated and focused by a series of lenses. The focused beam of electrons is then scanned across the surface of the sample.
As the electron beam scans the sample, it interacts with the atoms in the sample. This interaction causes the atoms to emit secondary electrons. Secondary electrons are low-energy electrons that are emitted from the surface of the sample. The number of secondary electrons that are emitted depends on the atomic number of the atoms in the sample. Higher atomic number atoms emit more secondary electrons than lower atomic number atoms.
The secondary electrons that are emitted from the sample are detected by a detector. The detector is located near the bottom of the microscope. The detector converts the secondary electrons into an electrical signal. The electrical signal is then amplified and used to create an image of the sample.
The image that is created by an SEM is a two-dimensional representation of the surface of the sample. The image shows the surface features of the sample in great detail. The resolution of an SEM image is typically between 1 and 10 nanometers.
SEMs are used in a variety of applications, including:
* Materials science: SEMs can be used to study the structure and composition of materials.
* Biology: SEMs can be used to study the structure of cells and tissues.
* Geology: SEMs can be used to study the structure and composition of rocks and minerals.
* Forensic science: SEMs can be used to examine evidence in criminal cases.
* Archaeology: SEMs can be used to study the structure and composition of artifacts.
SEMs are a powerful tool for studying the surface features of samples. They are used in a variety of applications and can provide valuable information about the structure and composition of materials.
