Low-temperature diffusion of implanted sodium in silicon

We have studied the low-temperature diffusion of sodium atoms implanted (at primary ion energy E = 300 keV to total doses within I broken vertical bar = 5 x 10(14)-3 x 10(15) cm(-2)) in single-crystalline silicon grown by the method of float-zone melting (fz-Si) with low oxygen concentration N (O) and by the Czochralski method in the presence of magnetic field (mCz-n-Si and mCz-p-Si) with N (O) a parts per thousand 5 x 10(17) cm(-3). The diffusion was studied at annealing temperatures within T (ann) = 500-420A degrees C for periods of time t (ann) = 72-1000 h. It is established that the temperature dependence of the diffusion coefficient D(10(3)/T) of sodium in fz-Si in a broad range of T (ann) = 900-420A degrees C obeys the Arrhenius law with E (fz) = 1.28 eV and D (0) = 1.4 x 10(-2) cm(2)/s. The same parameters are valid for the implanted sodium diffusion in mCz-Si in the interval of T (ann) = 900-700A degrees C. However, at lower temperatures, the values of D in mCz-Si are lower than to those in fz-Si, which is related to the formation of more complicated Na-O (n) (n > 1) complexes in the former case. Estimation of the diffusion activation energy of these complexes yields Delta E a parts per thousand 2.3 eV.