SELF-TRAPPED HOLES: THE Vk-CENTRE

Abstract

The self-trapped hole (Vk centre) is an important illustration of small polaron behaviour. In effect, the local lattice distortion and polarization it creates make it almost immobile, so it moves by incoherent hops from site to site. It is an example of charge localization: when there is also an electron that is in an excited state, one has energy localization, since energy can be released to cause local reactions. An electron and hole bound together, and localized because of the way they deform the crystal, are a self-trapped exciton.