Triboelectricity and Electron Traps in Insulating Materials: Some Correlations

Abstract

THE contact electrification between metals has been explained by Harper¹ in terms of electron transfer due to the difference of work function of the metals, but the frictional charge on insulating materials is not so easily explained. Frenkel² has suggested that the friction develops high temperatures locally and instantaneously so that electrons in the full band in the insulators can be excited to the conduction band and may then be transferred and trapped in impurity levels on the surfaces. Vick³ and Gonsalve⁴ also postulated the existence of surface electron levels and assumed that the electron transfer between insulators is determined by the differences in energy of these levels⁵. Fowler^6,7 has investigated the detailed distribution of electron traps in a number of insulators by measuring the conductivity induced by X-rays. We have carried out the measurement of triboelectricity on the same materials that were used in the study of X-ray induced conductivity⁶, in order to investigate the correlation, if any, between triboelectricity and the distribution of electron traps. These distributions had been derived from measurements of predominantly volume conductivity; but the effects of surface traps could not be excluded.