Graduation date: 1997

During the evaporative deposition of polycrystalline thin films, the development of a tensile stress at small film thicknesses is associated with island coalescence. Several continuum models exist to describe the magnitude of this tensile stress but the coalescence stress becomes significant at small enough thicknesses to draw the continuum models into question. For nanometer-sized islands, we perform atomistic simulations of island coalescence to determine if the atomistic methods and continuum models are mutually consistent. The additional detail provided by the atomistic simulations allows for study of the kinetics of island coalescence and the treatment of different crystallographic orientations. We find that the atomistic simulations are consistent with the continuum models. We also note that the atomistic simulations predict extremely fast coalescence times and include the possibility of island rotations during coalescence. / Singapore-MIT Alliance (SMA)

Polycrystalline films are used in a wide array of micro- and nano-scale devices, for electronic, mechanical, magnetic, photonic and chemical functions. Increasingly, the properties, performance, and reliability of films in these systems depend on nano-scale structure. In collaborative research with a number of SMA Fellows, Associates, and students, our group is carrying out research focused on probing, modeling and controlling nano-scale structural evolution during both vapor-phase and solid-phase polycrystalline film formation. In particular, high-sensitivity in-situ and real-time stress measurements are being used to study atomic scale forces and to characterize structure formation and evolution at the nano-scale. In other collaborative research, the affects of controlled structure and multi-film architectures on properties, such as piezoelectric characteristics and electromigration-limited reliability, are being explored. Through these interrelated activities, basic principles of the science and engineering of nano-scale materials are emerging. / Singapore-MIT Alliance (SMA)

A new computational method is introduced to investigate the stresses developed in the island-coalescence stage of polycrystalline film formation during deposition. The method uses molecular dynamics to examine the behavior of clusters of atoms both in free space and on substrates. Continuum treatments used in previous models may not be applicable at small length scales or low dimensionality. In atomistic simulations, the effects of surface diffusion, bond straining and defect formation can be directly studied. TEM experiments will be used to evaluate the validity of the simulation model. / Singapore-MIT Alliance (SMA)

Research on the processing, structure, properties and reliability of metal films and metallic microdevice elements is reviewed. Recent research has demonstrated that inelastic deformation mechanisms of metallic films and microelements are a function of temperature, encapsulation, and dimension. Reduced dimension can lead to strengthening or softening, depending on the temperature and strain rate. These results will help in the analysis and prediction of the stress state of films and microelements as a function of their thermal history. Experimental characterization and modeling of stress evolution during film formation has also been undertaken. New microelectromechanical devices have been developed for in situ measurements of stress during processing, and experiments relating stress and structure evolution are underway for electrodeposition and reactive film formation as well as vapor deposition. Experiments relating current-induced stress evolution (electromigration) to the reliability of Cu based interconnects are also being carried out. / Singapore-MIT Alliance (SMA)

Thesis (Ph. D.)--University of Washington, 1985. / Vita. Bibliography: leaves [135]-145.

Thesis (Ph. D.)--Georgia State University, 2006. / Title from title screen. Nikolaus Dietz, committee chair; Brian Thoms, Mark Stockman, Vadym Apalkov, Douglas Gies, committee members. Electronic text (167 p. : ill. (some col.)). Description based on contents viewed Apr. 24, 2007. Includes bibliographical references (p. 162-167).

Thesis (M.M.S.E.)--University of Delaware, 2006. / Principal faculty advisors: Robert L. Opila and Robert W. Birkmire, Dept. of Materials Science & Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (M.Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.