有機不揮発性メモリ素子モデル界面としての2-amino-4,5-imidazoledicarbonitrile (AIDCN)−金属界面の電子構造

2-amino-4,5-imidazoledicarbonitrile (AIDCN) is known as a promising material for organic nonvolatile memory application, and it has been reported that the performance of the AIDCN-based devices strongly depends on electrode metals. In the present study, we carried out photoemission spectroscopy (PES) measurements on the organic-on-metals (Ag and Al) and metals-on-organic model interfaces of an AIDCN-based memory device. The AIDCN overlayers on the Ag surface formed a sharp interface without apparent chemical interaction, while clear signs of a chemical reaction between the metal and AIDCN and formation of Al clusters in the AIDCN overlayers were revealed on the Al surface. Tendencies of the vacuum level shift and the highest occupied molecular orbital (HOMO) positions depending on the AIDCN coverage looked similar irrespective of the substrates. In the case of the metals-on-organic interfaces, in contrast, the shifting tendencies were opposite depending on the top-electrodes;the Ag-on-AIDCN interface showed upward band-bending with increasing the metal thickness, whereas downward bend-bending was observed for the Al-on-AIDCN interface. A possible origin of the band-bending is explained as intercalation of Ag or Al that behaves as acceptor- or donor-centers, respectively, into the AIDCN film.