9528513 Tsong This research project uses a unique combination of ultrahigh vacuum (UHV) microscopies: low energy electron microscopy (LEEM) and scanning tunneling microscopy (STM), to conduct in situ deposition and growth studies on Si surfaces to clearly identify different growth modes, i.e. Frank-van der Merwe, Volmer-Weber, and Stranski-Krastanov, and also to observe gross changes of the surface during growth, such as faceting and step-bunching. The investigation focuses on tailoring the surface morphology of homoepitaxial and heteroepitaxial layers on Si surfaces with different orientations. Ge/Si(100) and Ge/Si(311) and the homoepitaxial systems of Si/Si(100) and Si/Si(311) will be studied. Real-time LEEM observations of the development of 2D-island density during growth with and without a surfactant will be used to assess whether or not the presence of surfactants increases or reduces the diffusion lengths of adatoms to promote layer-by-layer growth. %%% The proposed LEEM/STM investigations are expected to pinpoint the role of energetics versus kinetics played by the high-index (311) substrate surface. STM, with its better spatial resolution, is ideal for the study of the initial stages of nucleation; while LEEM is particularly suited to examine growth kinetics dependent upon substrate temperature, diffusion rates and mass transport. These two powerful lateral spatial resolving techniques will enable identification of critical parameters necessary to tailor growth morphologies, and hence the synthesis of new and improved materials for microelectronic applications. The Ge/Si system is significant from the technological point of view of enhanced carrier mobility in SiGe/Si superlattices and their application in heterojunction bipolar transistors, while Si/Si homoepitaxy is a model system to study fundamental mechanisms controlling growth kinetics, in particular the minimization of substrate temperature for step-flow growth. The knowledge and understanding gained from this research pr oject is expected to contribute in a general way to improving the performance of advanced devices used in computing, information processing, and telecommunications by providing a fundamental understanding and a basis for designing and producing improved materials. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. ***
