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Transitor Damage Characterization by Neutron Displacement Cross Section in Silicon: Experimental

V. V. Verbinski, C. Cassapakis, R. L. Pease, H. L. Scott

Nuclear Science and Engineering

Volume 70 / Number 1 / April 1979 / Pages 66-72


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The validity of the silicon displacement cross section, D(E), was investigated by simultaneous measurements of neutron spectra (E) and of the accumulated damage D = K induced in 2N2222A transistors. The measured values of (E) were folded in with D(E) to obtain eq, the 1-MeV equivalent fluence for damage to silicon, and the ratios D/eq = K/eq ≡ K were obtained for diverse shapes of (E) to determine the stability of K to (E) variations. The value of K was seen to be constant (within 4 to 5%, 1σ) within roughly the same standard deviation as the D = K measurements for two modified reactor spectra that varied by as much as 1000% above a few MeV when normalized at the 0.2-MeV “threshold” of D(E). This helps substantiate the validity of D(E) in characterizing diverse neutron fields for radiation damage of a practical silicon transistor. Earlier studies with large-volume silicon diodes, for monoenergetic neutrons of 0.7 to 14 MeV, tend to corroborate the D(E) validity for transistors over this energy range. These results attest to the accuracy of the shape in terms of gross structure of D(E), which is governed by the accuracy of the ENDF/B-IV neutron cross-section evaluation used and of the Robinson functional representation of the Lindhard factor for determining the fraction of recoil-atom and charged particle kinetic energy that is available to cause displacements.

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