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| Defined coverage loudspeaker horn |
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| Muffler |
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Apparatus for determining the density of unoccupied electronic states of a material
| Details |
Inventors: Baptist, Robert; Chauvet, Gerard;
Assignee: Commissariat a l'Energie Atomique (Paris, FR)
Primary Examiner: Howell; Janice A.
Assistant Examiner:
Attorney, Agent or Firm: Pearne, Gordon, Sessions, McCoy, Granger & Tilberry
The invention relates to an apparatus for determining the electron states of a material. This apparatus comprises an enclosure containing a material, means for producing electrons of energy E.sub.i such, that on then penetrating the material, they acquire an energy E.sub.f below E.sub.i, accompanied by an emission of photons having different wavelengths. The apparatus also comprises another enclosure equipped with a tube entering the vacuum enclosure and provided with an entrance slit and another tube provided with a regulatable exit slit. The apparatus also comprises a grating located in the other enclosure and etched with lines, whilst being able to rotate about an axis parallel to these lines in order to select photons of the same wavelength. The apparatus finally has means for detecting the selected photons. Application to the determination of the forbidden band of a semiconductor. |
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DETAILED DESCRIPTION The present invention relates to an apparatus which obviates these disadvantages and in particular makes it possible to work in a wide wavelength range.
The apparatus according to the invention in particular makes it possible to detect and analyse photons, whose energy is between 10 and 100 eV, i.
e.
whose wavelength is between 100 and 1000 .
ANG.
.
More specifically, the present invention relates to an apparatus for determining the density of the unoccupied electron states of a material located above the Fermi level and for carrying out the analysis by ultraviolet fluorescence of a material excited by electrons comprising a vacuum enclosure which can contain a sample of a material; means for creating an electron beam of energy E.
sub.
i having an adequate intensity to ensure that their interaction with the sample can easily be detected, the electrons then acquiring energy levels E.
sub.
f below E.
sub.
i, the passage between the two energy levels accompanying an emission of photons, whose energy hv.
sub.
if is such that hv.
sub.
if =E.
sub.
i -E.
sub.
f ; means for performing a scan in energy E.
sub.
i ; and means for measuring the radiation coming from the sample; wherein the measuring means are placed under a vacuum and comprise a second enclosure provided with two tubes, which are inclined relative to one another, a first tube entering the vacuum enclosure, provided with a regulatable width entrance slit located in the vacuum enclosure, and a second tube provided with a regulatable exit slit; a diffraction grating able to rotate about an axis parallel to the etching marks thereof, enabling the selection of one of the wavelengths of the emitted photons, said grating being located in the second enclosure; means for rotating the said grating, its rotation angle being linked with the selection of the wavelength; and means for detecting photons of the same wavelength selected by the grating, said means facing the exit slit.
According to a preferred embodiment of the invention, the grating permits the selection of wavelengths between 100 and 1000
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