Longitudinal Muon Spin Depolarization in Ge-Rich SiGe Alloys

Abstract

We report preliminary results of our most recent LF-mu SR investigations of Mu site-and charge-state transitions in the Czochralski-grown Si0.09Ge0.91 alloy. The experiments reported here constitute the latest component of a large-scale project examining energy levels and electronic structure of Mu defect centers across the full alloy range for bulk Si1-xGex. Prior MuSR observations in Ge-rich alloys have indicated that states originating as Mu(T)(0) undergo a cyclic process. The present LF muon spin depolarization measurements examining the associated dynamics show slow and fast cyclic processes at high and low fields, respectively. The transition from the fast to slow charge-exchange regime occurs near B=70mT for this sample. A temperature scan at this specific applied LF produced some compelling results. Trends in relaxation rates and transition energies that are strongly dependent on Ge content suggest a model for the various components of the observed cyclic dynamics. We discuss the processes that may be responsible for this observed behavior. Combined with the previous mu SR data on the same sample, current results more clearly identifies the involved Mu species and transition dynamics among them. We will discuss Mu states and the picture of the dynamics for transitions among these states emerging from our most recent LF-mu SR measurements.