TECHNICAL: PI plans to characterize stress evolution of electrodeposited films in real time and correlate it with the microstructural evolution during growth. Two types of deposition will be investigated: (a) Volmer-Weber growth on amorphous substrates; (b) heteroepitaxial deposition by defect-mediated growth. An in-situ substrate curvature apparatus that has been designed and optimized for use in an electrochemical cell will measure the stress. The microstructural characterization will be performed by TEM, SEM, and AFM. In the case of the Volmer-Weber grown films, these characterizations will give island/grain sizes and island/grain size distributions, as well as indicate when the films first become continuous. Systems to be studied include Ag, Cu, Ni, and Co. The stress generation and relaxation behavior will be compared with the stress behavior observed in films grown on amorphous substrates by physical vapor deposition (PVD) methods. Quantitative comparisons will be made between the measured stresses in the electrodeposited films and the values predicted by the models that have been put forth to explain the stress behavior in PVD films. These results will indicate what features of intrinsic stress generation are generally applicable to all deposition methods and which are specific to electrodeposition. Heteroepitaxial deposition of Ag on Au by defect-mediated growth will be performed using Pb or Cu as the mediating species. Sensitive real time stress measurements will be used to characterize the process from a thermodynamic and kinetic stand-point as well as to optimize the process. NON-TECHNICAL: The planned research will address fundamental issues related to thin film formation and stress generation during electrochemical deposition that will have important technological ramifications. The ability to understand and control stress development will impact the processing of nanoscale materials in areas such as thin film interconnects and MEMS, where electrodeposition has been demonstrated to be a versatile synthesis method. The undergraduate and graduate students conducting the research will receive instruction and training in a variety of important scientific and technological areas, including thin film deposition methods and micromechanical testing. The PI plans to take advantage (as he has in the past in his capacity as Educational Outreach Coordinator for the Johns Hopkins MRSEC) of the various educational outreach programs of the Center, including REU funding and recruiting programs to increase diversity. As he has done for the past several years, the PI will involve a high school teacher (through a Research Experiences for Teachers program) and a high school student (which in previous years has included women and members of underrepresented minorities) in the research during the summer. As part of the research effort, the PI will develop a new course, for advanced undergraduates and graduates students, on the micromechanics of thin films and nanomaterials. A key component of the course will be laboratory demonstrations including thin films deposition by sputtering and electrodeposition and real-time intrinsic stress evolution. Other components of the course will involve characterization of thin films, nanomaterials, and surfaces using scanning tunneling and atomic force microscopy as well as nanoindentation.
