mu-SR investigations in silicon

Results on the temperature dependence of the residual polarization of negat ive muons in silicon with phosphorus (4.5 x 10(18), 2.3 x 10(15), and 3.2 x 10(12) cm(-3)) and aluminium (2.4 x 10(18) and 2 x 10(14) cm(-3)) impuriti es are presented. The muon spin rotation (mu SR) experiments were carried o ut in a magnetic field of 0.2. T and in the temperature range 4.2-300 K. In all investigated samples a relaxation of the muon spin and a shift of the spin-precession frequency were observed. The frequency shift (relative to t he room-temperature value) amounts to 7x10(-3) at 15 K. In the sample with a high concentration of phosphorus impurity (4.5 x 10(18) cm(-3)) damped an d undamped components of the muon spin polarization were observed at T < 30 K. Hyperfine interaction between the magnetic moments of the muon and that of the electron shell of the muonic atom (acceptor centre -Al-mu) is estim ated on the basis of the muon spin precession frequency shift data. The tem perature dependence of the spin-lattice relaxation rate of the magnetic mom ent of the shallow acceptor centre in silicon in the absence of external st ress is determined for the first time. It is found that the relaxation rate is well approximated by the power function v(T) = CTq, where the parameter q lies between 2 and 3. (C) 2000 Elsevier Science B.V. All rights reserved .