pyyhkäisyelektronimikroskooppi

Pyyhkäisyelektronimikroskooppi, often abbreviated as SEM (Scanning Electron Microscope), is a type of electron microscope that scans a focused beam of electrons across the surface of a sample. The interaction of the electron beam with the atoms on the sample surface generates various signals. These signals are then detected and analyzed to produce an image of the sample's surface topography and composition.

SEM works by directing a beam of high-energy electrons onto the specimen. As the electrons interact with the sample, they can generate several types of signals, including secondary electrons, backscattered electrons, and X-rays. Secondary electrons, which are low-energy electrons ejected from the sample, are most commonly used to form the image and provide detailed information about the surface's topography. Backscattered electrons, which are high-energy electrons that bounce off the sample, are sensitive to the atomic number of the elements present, allowing for compositional contrast. X-rays emitted from the sample can be analyzed by energy-dispersive X-ray spectroscopy (EDS) to determine the elemental composition of specific areas.

SEM instruments typically require samples to be conductive or to be coated with a conductive material, such as gold or carbon, to prevent charge buildup. The images produced by SEM have a high resolution and a large depth of field, making them suitable for examining a wide range of materials, including biological samples, geological specimens, and manufactured components. The applications of SEM are vast, spanning fields like materials science, biology, geology, and engineering for research, quality control, and failure analysis.