μ −SR investigations in silicon

Abstract

Results on the temperature dependence of the residual polarization of negative muons in silicon with phosphorus ( 4.5×10 18, 2.3×10 15 , and 3.2×10 12 cm −3 ) and aluminium (2.4×10 18 and 2×10 14 cm −3 ) impurities are presented. The muon spin rotation (μSR) experiments were carried out 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 the room-temperature value) amounts to 7×10 −3 at 15 K. In the sample with a high concentration of phosphorus impurity ( 4.5×10 18 cm −3 ) damped and 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 – μAl) is estimated on the basis of the muon spin precession frequency shift data. The temperature dependence of the spin-lattice relaxation rate of the magnetic moment of the shallow acceptor centre in silicon in the absence of external stress is determined for the first time. It is found that the relaxation rate is well approximated by the power function ν( T)= CT q , where the parameter q lies between 2 and 3.