Direct probing of the effective surface layer thickness during surface electrical breakdown along the solid dielectric and gas interface
Abstract
Surface property plays a crucial role in the surface electrical breakdown or surface flashover. Although the main electronic processes have been proposed, it is still not clear how thick the surface layer is involved in the interaction with the transporting carriers. In the present study, the effective surface layer thickness (Lf) of an isotactic polypropylene (iPP) is directly probed by precisely manipulating the iPP layer thickness (diPP) deposited on glass substrates. It is found that the direct-current surface flashover voltage varies significantly with diPP from 17.5 kV of the bare glass substrate to the saturated value of 21.0 kV when diPP exceeds 200 nm. The flashover voltage shows an exponential dependence on diPP, from which Lf is estimated about 45 nm. Morphologies of iPP thin films are investigated by atomic force microscopy, which exhibits film thickness dependent growth behaviour from a discontinuous layer with scattered iPP agglomerates to continuous layer with seaweed-like structure enclosed by amorphous boundaries. It is concluded that the main electronic interaction between transporting carriers and iPP is confined within the 200 nm thick surface layer, signifying the importance of its morphological and electrical properties in the further understanding and improvement of the surface flashover.
- Publication:
-
Applied Surface Science
- Pub Date:
- December 2019
- DOI:
- 10.1016/j.apsusc.2019.143812
- Bibcode:
- 2019ApSS..49843812Z
- Keywords:
-
- Solid-gas interface;
- Surface electrical breakdown;
- Effective surface layer;
- Thin polymer film;
- Structure-property relation