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Electron Microscopy Equipment

The scanning electron microscope (SEM) is a research tool used for high-resolution imaging of an object’s surface, as well as for studying morphology, chemical composition and other properties of subsurface layers of a nano-scale object. A focused beam of electrons scans a sample, and the intensity of secondary and backscattered electrons emitted from the sample is interpreted to form an image of the object’s surface. Primary electron beam is generated by the electron gun and focused by electromagnetic lenses. Scan coils divert the beam in such a way that it would scan the surface of an object, moving in a raster scan pattern. The wavelength of an electron is significantly shorter than that of visible light. Therefore, electron beam is used to image nano-scale objects with the resolution of up to 0.5 nm, which cannot be achieved by means of optical microscopy due to the diffraction limit.

Figure 1. Operation of a scanning electron microscope.

The transmission electron microscope (TEM) is used for imaging of ultra-thin samples. A beam of electrons is transmitted through a sample; the resulting flow of electrons is then magnified by electromagnetic lenses and visualized on a fluorescent screen or detected by a CCD imager. In such a way, the contrast is formed due to different absorption and dispersion by various fragments of the sample. TEM allows imaging at a resolution better than 0.1 nm.

Figure 2. Operation of a transmission electron microscope.

The nano-manipulator is a robotic system used for highly accurate transfer of nanoscale objects or their parts simultaneously with their imaging by SEM. The nano-manipulator contains an object table equipped with a few thin probes having the tip size of 100 nm. Each probe has three degrees of freedom: change of angle in vertical dimension, moving along the tip direction in horisontal dimension, and moving across the tip direction in horizontal dimension. Moving along all three axes is accomplished by precise drivers with the resolution of 0.5 nm in horizontal dimension and 5 nm in vertical dimension.

Figure 3. Photo image of a nano-manipulator.

See descriptions of microimages in Interpreting Electron Microscopy Data.