This project focuses on atom-resolved dynamical studies of the role of incident and adsorbed H atoms in the growth of low-temperature electronic materials by chemical vapor deposition (CVD). The approach is to address the complex behavior of H atoms by performing a wide range of atom-resolved dynamical measurements using scanning tunneling microscopy (STM). Initial studies will examine the behavior of molecular SiHX fragments produced by dissociative reaction of gas phase growth precursors such as disilane with a Si(100) surface. The diffusion and/or decomposition of these species in real-time will be followed to determine the role of neighboring vacancy (dangling bond) sites. The studies will be performed under largely passivated conditions that mimic real low-temperature growth environments. Vacancy sites will be deliberately generated under controlled conditions where they can be induced to collide with the molecular fragments. The rates and energy barriers to diffusion and decomposition will be directly measured, as will the influence of incident H-atoms on these processes. The detailed mechanism of H2 desorption from the Si(100) surface will also be probed in real-time. These measurements will be performed at temperatures where H-atoms, and hence the dangling-bond products of desorption, are mobile surface species. Particular attention will be paid to the role of defects and surface steps in the desorption process. Using an ion-beam, controlled defect densities will be generated to determine their impact on surface diffusion, recombination and H2 desorption. The role of ion-induced H2 or H-atom removal will also be investigated and compared with the thermally activated desorption mechanism. Using this approach a fundamental understanding of H-atom dynamics and Si growth is expected to be established helping to form the basis for controlled growth of advanced low-temperature materials. %%% The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new aspects of electronic/photonic devices. Experimental tools are now available to allow atomic level observation of elementary surface processes which when better understood allow advances in 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. ***
