9804310 Drucker This project addresses self-assembly of heteroepitaxial semiconductor coherent island quantum dots. The approach is to study atomistic mechanisms of self-assembly in the Ge/Si(100) system; since, although Ge/Si(100) is the simplest system for which self-assembly has been observed, it retains much of the self-assembly related behavior observed in more complex alloy semiconductor systems such as SiGe/Si, InGaAs/GaAs. A variety of in and ex situ microscopies (scanning tunneling, atomic force and scanning and transmission electron microscopies) will be employed to characterize ensembles of self-assembled quantum dots (SAQD) formed using molecular beam epitaxy (MBE) and chemical vapor deposition (CVD). The phase-space of experimentally accessible parameters; substrate temperature, deposition rate, total coverage and postgrowth annealing, will be systematically investigated in order to identify pathways to obtaining desired size and shape uniformity throughout the ensemble of SAQD. A primary goal is to obtain this uniformity while retaining the flexibility for varying the mean radius of the dot size distribution and the areal density of the dots from sample to sample. The observed morphology of the Ge/Si(100) SAQD will be correlated with their optical properties using photoluminescence spectroscopy. The experimental investigations will be complemented by further development of a model of microstructural evolution in strained island systems. This model incorporates the elastic energy of coherent islands and a diffusion bias away from strained islands which increases with island size. Further insight into the self-assembly process will be gained through kinetic Monte Carlo simulations of strained island growth. %%% The project addresses basic research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to important aspects of electroni c/photonic devices. Experimental tools are now available to allow atomic level observation of elementary processes which when better understood will allow advances in both fundamental science and technology. The basic knowledge and understanding gained from the research is expected to contribute to improving the performance and stability of advanced devices and circuits by providing a fundamental understanding and a basis for designing and producing improved materials, and materials combinations. 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. ***
