| Budget Amount *help |
¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1997: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1996: ¥800,000 (Direct Cost: ¥800,000)
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| Research Abstract |
The more electrical and electronic apparatus and other equipment using insulating composites are nimiaturized, the more strong electric fields apply their insulating layr. The charge-exchange rate at the insulator-insulator interface in insulating composites is affected by the direction of carrier transport and carrier species. Such asymmetric characteristics are widely seen in insulating composites e. g. RE-EVA and epoxy-alumina and seem very important to understand the insulation performance of composites. In order to clarify the asymmetric properties on the basis of electronic levels, such as Fermi level, ionization potential, electron affinity and effective electron or hole conduction levels, the methods for estimating electronic levels in ploymers were discussed. In this paper, electronic levels in insulating polymers were estimated by contact potential defference XPS,UPS in air and photoinjection current and the correlation among the estimated levels was investigated.
Ionization p
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otential (Poly-2-Vinyl Pyridine-Co-Stirene), PMMA (polymethyl-methacrylate), PS (polystirene) snd PVK (Poly-N-Vinyl-carbazole) were estimated by adding the work function measured by Kelvin method and binding energy estimated from the XPS spectrum. In PVK,the electronic level estimated by photoinjection current method was consistent with that by Kelvin method and XPS.However, In PS and PMMA,the electronic level estimated by that did not coincide with the upper edge of valence band estimated from Kelvin method and XPS and corresponded to effective donor level which contribute to hole conduction. The UPS measurement in air seemed to be able to observe tail of electronic levels near Fermi level which were responsible for contact electrification.
The electronic states on polymer surface were easily changed by adsorption of water or other molecules, change in morphology and so on. On the other hand, the contact potential difference between polymers and reference materials (Au or ITO) decteases with UV treatment for polymers. This shows that Kelvin method is highly sensitive to observe the change of the electronic states on polymer surface with heat and UV treatment which might be related to degradation of polymers by heat or UV.
It seems that this investigation contributed to the establishment of the methods for estimating electronic levels in insulating polymers. Less
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