Transmission electron microscope
Scanning electron microscope
Electron probe microanalyzerOptical microscopes use light. However, electron microscopes use an electron beam instead of light. The wavelength of the electron beam is so much smaller than that of visible light that the electron microscope can clearly observe structures in much greater detail. The electron beam cannot freely move in the air. Therefore, the path of the electron beam in the device is under a vacuum. Because the samples are placed in a vacuum, biological samples cannot be observed under natural or "wet" conditions. In order to reduce morphological damage, the samples need to be dehydrated and the appropriate treatments to increase the quality of the electron microscope images need to be conducted on the samples.
Transmission electron microscope (TEM)
The electron beam irradiates the specimen and the distribution of transmitted electrons form an image on a fluorescence screen. These images can be recorded on film or by a CCD camera. TEM is used mainly to observe the interior structure of samples. The permeability of specimens to electrons beam is low, therefore, the samples should be cut or polished in ultra thin sections (thickness: > 100 nm). In JAMSTEC, this device is used for the observation of bacterial flagella and the cells of deep-sea organism.
Scanning electron microscope (SEM)
A focused electron beam scans the surface of the specimen and secondary electrons that are generated from the surface of the specimen are detected. SEM enables observation of the surface structure of a sample in three dimensions and in great detail through a computer monitor. In JAMSTEC, this device is used for observation of the surface structures of the cells of the deep-sea organisms. In the case that the conductivity of a sample is poor, as is usual for biological samples, samples need to be thinly coated with metal.
Electron probe microanalyzer (EPMA)
The focused electron beams scan the surface of the specimen. Consequently, characteristic x-rays, secondary electrons and backscattered electrons are emitted. The characteristic x-rays have peculiar wavelengths depending on the types of atoms. EPMA can examine many characteristics, including the type, percent content, and distribution of chemicals in the samples by measuring the wavelength and intensity of characteristic x-rays. EPMA can also precisely confirm the point of analysis within the sample by detecting secondary electrons and backscattered electrons. In JAMSTEC, this device is used for examination of the chemical compositions and their distributions in mineral samples.
