Radiant energy – Inspection of solids or liquids by charged particles – Electron microscope type
Patent
1996-08-12
1998-09-22
Anderson, Bruce
Radiant energy
Inspection of solids or liquids by charged particles
Electron microscope type
250397, 250310, H01J 37244
Patent
active
058118047
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an electron microscope provided, in the direction of the longitudinal axis, with at least one electron beam generation system, a condenser and objective lens system, a specimen chamber with a specimen mount, a projection lens system with an imaging screen for the purpose of transmission electron microscopy (TEM) and/or an electron detector for the purpose of scanning electron microscopy (SEM), for use in combination with an externally positioned Raman spectrometer and an associated light source for injecting and extracting, via a window in the microscope wall, a light beam to be directed at the specimen, and specimen-related Raman radiation, respectively. Such a microscope is disclosed by the French Patent Application FR-A-2596863.
BACKGROUND OF THE INVENTION
The electron microscope generally known from the prior art is an instrument by means of which it is possible for structures in thin specimens or surfaces to be rendered visible, for example by means of TEM, or for structures in bulk specimens to be rendered visible, for example by means of SEM, with high resolving power, in the order of magnitude of a few tenths of nanometres in the former case or of a few nanometres in the latter case.
In such a microscope, as depicted in FIG. 1, an electron beam 1 is produced in an electron gun 2 consisting of cathode, Wehnelt cylinder and anode. With the aid of a magnetic lens system 3, a so-called condenser lens system, the electron beam is focused into a coherent spot above the specimen 4, which spot may be subjected to a scanning notion.
In the case of the transmission electron microscope (TEM) the beam passes through the specimen 4 and is projected with the aid of a magnetic lens system, such as objective 5 and projection lenses 6, onto an imaging screen 7 such as a fluorescent screen. Upon incidence of the electron beam, this screen lights up and produces a magnified image of the specimen. The presence, in the specimen, of elements having varying atomic numbers results in contrast being achieved, heavy elements having a high atomic number affecting the electron trajectory in a different way than do light elements having a lower atomic number. The result of this is that, at positions where heavy elements are present, the electrons are reflected in their entirety or in part, while electrons can pass through fairly easily at positions where light elements are present. Consequently, a specimen composed of different chemical elements will therefore also transmit varying quantities of electrons. On the screen an image is formed which gives the highest brightness for positions where light elements having lower atomic numbers are present in the specimen, and the lowest brightness at positions where elements having a high atomic number are present. A sort of shadow image is thus formed.
In the case of the scanning electron microscope (SEM) which is depicted in FIG. 2 and which is essentially of the same construction as the transmission electron microscope, the electron beam 1 generated by an electron gun 2 also passes through a condenser lens system 3. The electron beam, in the case of the SEM, is focused onto a spot on the specimen, said spot being subjected to a scanning motion by means of a deflection unit 10. The electrons reflected or backscattered by the specimen 4 are intercepted at an electron detector 8 and, after amplification in 11, are used to effect intensity variations on the screen of a cathode ray tube 12 synchronized with the electron beam scanning.
The TEM provides images of thin specimen cuts and can therefore render visible the interior of specimens to be studied. In contrast, the SEM provides an image with the aid of the electrons returning from the specimen and is therefore specifically suitable for presenting images of the surface, or directly below it, of a specimen. If the specimen to be studied is a section through an object, the SEM will naturally also provide information on the interior. It is also possible, in the SEM, for the reflected el
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Greve Jan
Koerten Hendrick Klaas
Van Blitterswijk Clemens Antoni
Anderson Bruce
Biomaterials Research Group Stichting Azl
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