Charge transfer from metal to dielectric by contact potential

Abstract

Equations are derived for the charge transferred between a metal and a dielectric by a difference of contact potential, assuming a dielectric having traps, or `self-traps', at a single energy level and no restriction on carrier density by `trap filling'. A limit to the carrier density is then set by quantum considerations, which the theory predicts will become important at a contact potential difference of 0·5 V for normal temperatures and dielectric thicknesses around 10−4 m.A solution for such a system is derived using only classical electrical theory and simple thermodynamics. The results are compared with measurements on six types of plastic film already reported by Davies, and satisfactory agreement is found, including the predicted limit at 0·5 V.In addition to the charge transferred, the theory also predicts the potential and carrier density distributions in the dielectric, and therefore the electrical conditions within a slab of dielectric (of the type described) bounded by short-circuited conducting electrodes.

Charge transfer in metal/polymer contacts

“…The strongest evidence for the role of electrons comes from the observation that charge transfer between metals and some insulators varies systematically with the work function of the contacting metal (Shaw 1917, Arridge 1968, Davies 1969. Furthermore, the relationship between the charge and the work function can in principle provide a critical test of theories of contact electrification: various theories have predicted quite different relationships between charge and work function (Davies 1969, Chowdry and Westgate 1974, Hays 1974, Lowell 1979, Hersh and Montgomery 1956, Garton 1974, Duke and Fabish 1978. A considerable number of experimental investigations of the charge/work function relationship have been reported (most of them concerned with polymers) 0022-3727/87/050565 + 14 $02.50 @ 1987 IOP Publishing Ltd but no clear-cut conclusions emerge.…”

Density of Surface States: Another Key Contributing Factor in Triboelectric Charge Generation

“…In such the electroncloud−potential-well model as shown in Figure 1a, atoms from any two contacted surfaces with overlapped electron clouds will exchange electrons, as driven by the difference in the electronoccupied levels. 18,24 Commonly, the material with the lower occupied level is more electronegative and easily accepts electrons from the material with the higher occupied level (electropositive), and thus it usually takes a more negative position in the triboelectric series (Figure 1b). In triboelectric series, PET shows more negative than Kapton, which is also confirmed by the work functions of them (Kapton: E 1 = 4.88 eV,…”

“…It has been confirmed that electron transfer due to the overlap of electron clouds dominates the CE for many material pairs especially metal–polymer pairs, , and at least it is an inevitable mechanism in CE. In such the electron-cloud–potential-well model as shown in Figure a, atoms from any two contacted surfaces with overlapped electron clouds will exchange electrons, as driven by the difference in the electron-occupied levels. , Commonly, the material with the lower occupied level is more electronegative and easily accepts electrons from the material with the higher occupied level (electropositive), and thus it usually takes a more negative position in the triboelectric series (Figure b). In triboelectric series, PET shows more negative than Kapton, which is also confirmed by the work functions of them (Kapton: E 1 = 4.88 eV, PET: E 2 = 5.21 eV). , We measured the surface charge polarity after rubbing PET and Kapton together, which shows the PET surface takes negative charge density of 0.46 nC/cm 2 , which confirms the triboelectric series and indicates the relative occupied levels between Kapton and metals, as shown in Figure c.…”

Generation of the second harmonic of laser radiation in noncentrosymmetrical polymeric systems

“…33 Even in the absence of the external potential difference, the charge up to * 10 78 C cm 72 is deposited on the surface of the dielectric polymeric film, when it comes in a contact with the metal owing to contact charging. 55,56 It is shown 33 that the SHG characteristics are independent of the film conductivity, if the charge carrier concentration is several orders of magnitude smaller than the concentration of the chromophore. For example, for the film PIBMA + 1 mass % of DANS these concentrations are 10 10 ± 10 15 and 5610 19 cm 73 , respectively.…”