Roles of quantum dot like multi-functional traps in electrical conduction of polymer nanocomposites

Abstract

Nano-flllers may act as quantum dots (QDs) in polymer nanocomposites. Permittivity, space charge and treeing were discussed in terms of QDs elsewhere (IEEE ICD 2016, Montpellier and IEEE DEIS 2016, Toronto). In this paper, electrical transport is discussed, when nanofillers behave like QDs. As a result, fillers must become multi-functional traps. In the low electric field, on one hand, they act as ordinary but newly introduced shallow and deep traps existing on their interfaces. Nano-fillers do not play as carrier traps due to Coulomb blockade (CB) effects. Therefore, trap-controlled conduction is probable with both original bulk traps and newly created interfacial traps. On the other hand, in the high electric field, they exhibit non-linear behaviors above a critical electric field. When electric field exceeds a critical CB field, charge carriers are likely to be confined into QD-like nanofillers possibly by tunneling. This is called the quantum confinement. Such charged QDs are so stable as to produce relatively long-lived space charge. This hypothesis can explain many aspects of dielectric phenomena experimentally observed thus far. This verification process is explained in the paper.