The depth profile of core energy levels: Electronic structure of buried organic/metal interfaces examined by X-ray photoemission and target factor analysis

We have developed a new experimental method of X-ray photoemission spectroscopy (XPS) that can map out the core-energy levels as a function of depth from the surface of the film. A series of XPS data are recorded with different detection angles and expanded to the Taylor series of angle-averaged spectra using the target factor analysis. This procedure enables conversion of the measured angle variations in XPS to the core energy levels as a function of depth from the surface. This method has been applied to profiling the electronic levels of buried interface between organic semiconductor and metal surfaces.