Magnetic resonance methods

In this chapter, we will focus on the study by EPR of point defects in semiconductor materials. Indeed, impurities, vacancies, anti -sites and complexes of them, in a diamagnetic material, may exhibit a local electronic reconstruction favoring unpaired electrons, and consequently, such defects have a nonzero electon spin. Of course, point defects may exist in an S = 0 state and then be EPR silent. Nevertheless, in semiconductors, most of the point defects have several charge states in the gap, and generally, each of them corresponds to a different spin state. Changing the defect charge state by electrical polarization or by light irradiation is then an efficient mean to reveal and detect the defects by EPR.