Molecular dynamics simulation of the trapping of electrons in sapphire lattice

The mechanism of electric charge trapping can be used to describe the storage of energy in dielectric materials. The analysis of the mechanism has been obtained by the space charge physics. Technical simulation such as molecular dynamics applied to this problem allows us to complete the preceding results with a dynamic approach. We show that an excess electron introduced into the sapphire lattice (α-Al₂O₃) can be trapped only at a limited number of sites. The energy gained by allowing the electron to localize in these sites is of the order of 4-5 eV, in good agreement with the results of the space charge model. Displacements of the neighboring ions due to the implanted charge are shown to be localized in a small region of about 5 Å. Detrapping is observed at 250 K. The ionic displacements turn out to play an important role in modifying the potential landscape by lowering, in a dynamical way, the barriers that cause localization at low temperature