Energy Level Alignment and Interfacial Electronic Structures at Organic/Metal and Organic/Organic Interfaces

Abstract

His thesis research focused on the metastable atom electron spectroscopy of clean and adsorbate-covered silicon surfaces. In 1991, he joined the Solid State Chemistry Laboratory, Nagoya University, Nagoya, Japan, where he is currently working as a research associate. His current research interests include electron spectroscopy of functional organic materials, electronic structure of organic/ inorganic interfaces, and molecular orientation of thin organic films. From 1995 to 1997, he was on leave at the Institute for Molecular Science, Okazaki, Japan, to investigate the electronic structure of organic/metal interfaces with synchrotron radiation.

Molecules and Electronic Materials

“…Such interface dipoles result from electronic interactions between the outermost atoms of the constituting phases. This effect of deliberately added interface dipoles is known from earlier work, [23] but their near-omnipresence in metal±semiconductor junctions is a rather recent suggestion [24,25] (Fig. 2).…”

“…There, interactions of organics (mostly p-bonded ones) with metals are investigated in depth by in-situ ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and Kelvin probe measurements, following deposition of the molecules on a metal or vice versa (see the literature [25] for a review). The molecules interact with the metal in several ways (see Fig.…”

Energy Level Alignment and Interactions at Potential Contacts for Spin Injection into Organic Semiconductors

“…[41,43] The downshift of the chemical potential for CuPc and a-6T on clean LSMO manifests itself in an upshift of the corresponding valence band spectra because the binding energy scale is The initial deposition of a-6T as well as of CuPc results in a rather abrupt change of the work function which gives a measure for the interface dipole at these interfaces. [20] In case of the clean interfaces there is also a slight energetic upshift for increasing layer thickness of the organic semiconductors, which parallels that of the core levels as discussed above. The presence of rather large interface dipoles at interfaces with organic semiconductors is a common observation for many systems, [20,21,28] and its origin is not yet fully understood.…”

“…This is most likely due to the fact that the clean LSMO substrate has on average a surface roughness of about 3 nm as seen in atomic force microscopy measurements, and the core level shifts result from the effect of inhomogeneous film growth and the formation of closed layers of the two organic semiconductors not until larger nominal film thicknesses, whereas the contamination layer provides a flatter surface and reduces this effect (see also refs. [20,21] ).…”

“…It is thus clear that the performance and characteristics of organic devices in general are significantly influenced by the interface structure and electronic properties, and it is no surprise that interfaces between metallic contacts and organic semiconductors have been studied extensively in the past. [20][21][22][23][24][25][26] Many of these interfaces are characterized by the presence of an interface dipole confined to a thin interfacial layer, whereas the origin of this interface dipole is not fully understood yet. [27,28] In regard of contacts between organic semiconductors and La 0.7 Sr 0.3 MnO 3 electrodes, only a few reports have been published recently.…”