Spectroscopy of semiconductor/insulator and metal/insulator interface dipoles.

The proposed research focuses on the physical mechanisms determining the energy alignment of electron states at the interface between two solids. While the classical Mott- Schottky theory predicts direct relationship of the interface barrier height with the bulk densities of electron states of the contacting solids, experiments reveal a by far more complex behavior indicative of additional dipole component(s). The goal of the present study consists in obtaining spectroscopic information regarding origin, conditions of formation, and basic physical properties of the interface dipoles formed at the interfaces of semiconductors and metals with oxide insulators. The most reliable and accurate information about barrier heights at solid interfaces is provided by internal photoemission spectroscopy which also allows one to reconstruct the distribution of the electrostatic potential. By combining this technique with several complementary spectroscopy methods such as inelastic tunneling, electron spin resonance, and capacitance measurements, we will address the structural and physical factors affecting the barrier. This includes chemical composition and atomic arrangement of interfaces between differently oriented crystals, the impact of adsorbates and interlayers, as well as electrostatic screening properties of the solids. In addition to revealing the fundamental trends in the interface dipole and the barrier evolution, the project intends to explore possibilities of interface barrier engineering which can then be exploited to realize the dezired functionality in electronic devices.