Determination of oxygen in metals and semiconductors by means of the 16O(T, n)18F reaction

Tritons accelerated up to 3.5 MeV by a Van de Graaff, were used to study the 16O(T, n)18F reaction, which was then applied to the analysis of oxygen in metals and semiconductors. Tritons are of great interest because of the characteristics of the 16O(T, n)18F reaction: positive Q-value; high cross-section at low energy; no nuclear interference below 4 MeV. The calculated sensitivity for the determination of oxygen is 0.5 ppb at 3.5 MeV. Si, Ti and Mo were analyzed non-destructively at 3.5 MeV and the results agreed with results obtained by other methods. Pure Ge and AsGa were analyzed non-destructively at 3 MeV and the detection limits were respectively 25 and 6 ppb. Triton activation is a very safe and simple method: irradiation, etching, counting. There are no lengthy and difficult chemical separations. The energy of 3.5 MeV, however, is a little too low for matrixes like Mo (or Ni, W, Ta,etc.), in which the range of tritons is only 25 to 30 micrometers. In this case, the precision is strongly limited by the accuracy of the control of the etching. (T.G.)