Atomic-Scale Controlled Assembly and Properties of Ionic Solid Films on Group Iv Semiconductor Surfaces
The Division of Materials Research, Directorate for Mathematical and Physical Sciences, National Science Foundation (NSF), USA announced the Program entitled “Materials World Network: Cooperative Activity in Materials Research between US Investigators and their Counterparts Abroad (MWN)” . The Department of International Programs, National Science Council (NSC) has called for counterproposals for this program. This proposal is organized in response to these new programs aiming to enhance opportunities for collaborative activities in materials research. Under the joint funding support from both NSC and NSF, this project is to investigate in depth the fundament science of ultra thin ionic crystals on group IV semiconductor surfaces by establishing a close collaboration between our research group and a renowned team led by Professor T.C. Chiang at the University of Illinois at Urbana-Champaign. The ability to understand, manipulate and control ultra-thin films of various kinds at the atomic and molecular level is one of the great challenges of modern research. On metal and semiconductor surfaces, much work has been carried out in the last decades for their fundament properties and for various overlaying thin-film systems such as metal, semiconductor, organic and amorphous dielectric thin films in the last decade. However, the growth behavior, growth control and interfacial properties of the crystalline ionic solids on the covalently bonded semiconductor substrates is relatively less studied and poorly understood to date. This project proposes to investigate the fundamental properties and ultimate control of ultra thin films of the ionic solids, in particular, the ultra-thin alkali halide (AH) on group IV semiconductors. The key approach is to combine the technical strength of the two groups. By employing high resolution microscopic and spectroscopic techniques, we are to observe the interface between the AH atomic layers and the semiconductor substrates. The work will include investigations and development of (1) the growth mode of various ultra-thin films of ionic crystals on the Si, Ge surfaces, (2) the atomic-layer-epitaxy (ALE) technique for alkali halides (AH) films, (3) atomic structure of the thin AH films, (4) charge transfer between the Si and Ge substrates and the AH layers, and (5) the band structure of 2D ionic solid films. The experimental techniques to be employed include synchrotron photoemission core-level (TAIWAN and US teams), angled resolved photoemission spectroscopy (US team), variable-temperature ultra-high-vacuum scanning probe microscopy (TAIWAN team), and synchrotron x-ray diffraction (US team). Other US and TAIWAN theoretical groups will also be involved in less formal settings.