AVS 47th International Symposium
    Surface Science Monday Sessions
       Session SS2+NS+TF-MoM

Paper SS2+NS+TF-MoM4
Theory of the Nucleation and Growth of Iron on GaAs

Monday, October 2, 2000, 9:20 am, Room 209

Session: Nucleation and Growth
Presenter: S.C. Erwin, Naval Research Laboratory
Authors: S.C. Erwin, Naval Research Laboratory
M. Scheffler, Fritz Haber Institute, Germany
Correspondent: Click to Email
By growing ultrathin films of ferromagnetic metals on semiconductor substrates, it is possible to create a partially spin-polarized electrical current in the semiconductor. This phenomenon is the starting point for a wide variety of magnetoelectronic devices based on the "spin-valve" effect, whereby an externally applied magnetic field can switch the current on and off. Considerable experimental effort has focused on ultrathin films of Fe grown by MBE on GaAs, in part because their small lattice mismatch results in nearly epitaxial films. Although a number of experiments have contributed to a detailed description of the phenomenology of magnetism in these films, little is known about the microscopic physics of magnetism at an intimate metal-semiconductor interface. We use spin-polarized density-functional total-energy methods to investigate the nucleation and initial growth phases of Fe on GaAs(001), focusing on the roles played by diffusion, magnetism, and defect chemistry. Our findings include the following results: (1) magnetism develops in the very first monolayer, and is in fact enhanced by the presence of the interface; (2) surface diffusion is strongly suppressed in the submonolayer regime by the tendency of Fe adatoms to form very stable Fe-As bonds. Finally, we discuss the influence of the initial GaAs reconstruction on the structure and magnetic properties of the Fe film.