Study on transport mechanism of carriers that go across the contact interface in insulating composite

使用绝缘复合材料的电气电子设备和其他设备的绝缘化程度越高，其绝缘层施加的电场就越强。绝缘复合材料中绝缘子-绝缘子界面的电荷交换速率受载流子输运方向和载流子种类的影响。这种不对称特性广泛存在于Re-EVA和环氧-氧化铝等绝缘复合材料中，对了解复合材料的绝缘性能具有重要意义。为了阐明基于电子能级的不对称性质，如费米能级、电离势、电子亲和势和有效电子或空穴电导能级，讨论了估算聚合物中电子能级的方法。本文用接触电势差XPS、空气中的UPS和光注入电流估算了绝缘聚合物中的电子能级，并研究了它们之间的相互关系。电离p…将开尔文方法测得的功函数和XPS谱计算的结合能相加，得到了更多的势(聚-2-乙烯基吡啶-co-苯乙烯)、PMMA(聚甲基丙烯酸甲酯)、PS(聚苯乙烯)和PVK(聚-N-乙烯基咔唑)。在PVK中，光注入电流法估算的电子能级与Kelvin方法和XPS的结果一致，而在PS和PMMA中，其估算的电子能级与Kelvin方法和XPS估计的价带上缘不一致，而对应于对空穴导电有贡献的有效施主能级。在空气中的UPS测量似乎能够观察到费米能级附近的电子能级尾部，这些电子能级负责接触带电，聚合物表面的电子态容易因水或其他分子的吸附、形态变化等而改变。另一方面，聚合物与标准物质(Au或ITO)之间的接触电势差随着聚合物的紫外光处理而减小。这表明开尔文方法对观察聚合物表面电子状态的变化具有很高的灵敏度，这种变化可能与聚合物受热或紫外光降解有关。这一研究似乎有助于建立估计绝缘聚合物中电子能级的方法。较少

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 … More 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