Muon Spin Relaxation, Rotation, Resonance, Research (MuSR) Experimental Technique as applied to semiconductors with current examples

This presentation is an overview of the Muon Spin Research (MuSR) techniques. MuSR utilizes muons in multiple ways. When implanted in a material, muonium (Mu) is formed and are sensitive to the local electronic and magnetic environment. Mu is a pseudo-isotope of hydrogen and used to study isolated H impurities/defects. As implanted, Mu^+/0/− is an experimentally accessible analogue to isolated H^+/0/−. Mu can be used to study ionic dynamics such as in Li− and Na−based energy storage applications. Muons are also used as a probe of magnetism in materials including applications in superconducting systems and novel materials.

In MuSR experiments, 100% spin polarized muons are created in particle accelerators and implanted in samples without causing any damage to the sample. The muons have a short lifetime and decay into a positron and two neutrinos. The positron is emitted preferentially along the Mu polarization at the time of decay and is tracked as a function of time. These data are interpreted to determine information such as Mu (H) formation, stability, charge state dynamics, motional dynamics, H-bonding configurations and magnetic order. This experimental technique has similarities to NMR and EPR. Examples of recent experimental results specific to semiconductors will be presented.