Factors Affecting Transmission Electron Microscope Resolution
Fine structures smaller than 0.2µm cannot be seen clearly under an optical microscope. These structures are called submicroscopic structures or ultramicroscopic structures.
structures; ultrastructures). To see these structures clearly, a light source with a shorter wavelength must be selected to increase the resolution of the microscope. In 1932, Ruska invented the transmission electron microscope (TEM) with an electron beam as the light source. The wavelength of the electron beam is much shorter than visible light and ultraviolet light, and the wavelength of the electron beam is inversely proportional to the square root of the voltage of the emitted electron beam. , that is to say, the higher the voltage, the shorter the wavelength. The current resolution of TEM can reach 0.2nm.
The imaging principles of electron microscopes and optical microscopes are basically the same. The difference is that the former uses electron beams as the light source and electromagnetic fields as the lenses. In addition, since the penetrating power of electron beams is very weak, specimens used for electron microscopy must be made into ultra-thin sections with a thickness of about 50 nm. This kind of slice needs to be made with an ultramicrotome. The magnification of an electron microscope can reach up to nearly one million times. It consists of five parts: electronic lighting system, electromagnetic lens imaging system, vacuum system, recording system, and power supply system. If broken down: the main part is the electronic lens and imaging recording The system consists of an electron gun, condenser, sample chamber,
Objective lens, diffraction lens, intermediate lens,
Projection mirrors, fluorescent screens and cameras.
An electron microscope is a microscope that uses electrons to reveal the interior or surface of an object.
The wavelength of high-speed electrons is shorter than that of visible light (wave-particle duality), and the resolution of a microscope is limited by the wavelength it uses, so the resolution of an electron microscope (about 0.1 nanometers) is much higher than that of an optical microscope (approximately 200 nm).
