Tunnelling between metals and insulators and its role in contact electrification

Abstract

Tunnelling of electrons between a metal and localised states in an insulator is considered, with a view to determining the charge that an insulator can acquire by this mechanism when it is contacted to a metal, and also the extent to which it can lose charge by back-tunnelling during separation. Traps at a single energy are considered primarily, but some attention is given to traps distributed over a range of energy. Back-tunnelling is likely to be significant only at the very highest observed charge densities.

On the nature of high field charge transport in reinforced silicone dielectrics: Experiment and simulation

“…For instance, Chen et al examined the interface dipole effect at a PE/Al interface using DFT calculations, and found that the interface dipole only causes a small energy shift of 0.2 ~ 0.3 eV, which is still too small to account for the large discrepancy between the experimentally measured energy barrier and the one predicted by theory 37 . Therefore it was often argued that charges can be directly injected to the deep trap states by phonon-assisted tunneling characterized with a much smaller barrier and without necessarily being excited over a larger energy barrier up to the conduction band edge or mobility edge 31,38,39 . This is consistent with the MH model that charge can move directly between different localized states by tunneling.…”

Tribo-electric charging and adhesion of cellulose ethers and their mixtures with flurbiprofen

“…During the contact charging process, the valence electron energy state of powder particles on an atomic scale is designated as the fermi level whilst the vacuum energy level is a thermodynamic state of electrons far from the atom and can be considered as a reference point. The difference between the fermi level and vacuum energy level equates to the work function (Ф), which is a unique surface property of materials and refers to the minimum energy difference required for the liberation of loosely bonded electrons present in the outer electron shells of an atom (Lowell, 1979). When inter or intra-particulate contacts of powder particles are established, electrons flow from the lower work function (Ф 1 ) towards the higher (Ф 2 ), consequently a potential difference (Ф 2 -Ф 1 ) is generated across the particle surface (Lang and Kohn, 1971).…”

The charging of microparticles in corona discharge in the air

“…Поверхностные состояния действуют как «ловушки» и обеспечивают накопление элек-тронов [7]. Обратное туннелирование пренебрежимо мало, если поверхность имеет не очень большой заряд [8].…”