Real-time imaging of surface evolution driven by variable-energy ion irradiation

Island embryo regression driven by a beam of self-ions in the linear regime

The kinetics of island growth and regression are discussed under the approximation of linear response, including the Gibbs-Thompson potential, for a reacting assembly of adatoms and advacancies (thermal defects) on a surface irradiated with a beam of self-ions. First the quasistatic growth or shrinkage rate, for islands of size n less than the critical size n, is calculated for the driven system, exactly, for linear response. This result is employed to determine successively: (i) the regression rate of driven embryo islands with n < n; and (ii) the structure of the steady state decay chain established when embryos of a particular size n0 < n are created by ion beam impacts. The changed embryo distribution caused by irradiation differs markedly from the populations of the embryos at equilibrium.

LEEM investigations of ion beam effects on clean metal surfaces: quantitative studies of the driven steady state

The technique of low-energy electron microscopy (LEEM) pioneered by Bauer has been adapted here to the investigation of ion beam processes on crystal surfaces by the incorporation of an intense and tunable source of selectable, energetic ions into a LEEM designed by Tromp et al. In this paper we explain principles that constrain the design of this tandem instrument, to permit observation of surfaces during irradiation. We also describe experiments that probe the driven steady state of surfaces subject to the perturbation of a uniform and constant flux of self-ions. The emphasis is on the example of Pt(-) ions irradiating the Pt(111) surface. We explore a regime of linear response at elevated temperature in which the driven nucleation and universal driven growth of surface islands, and the driven cycling of Bardeen-Herring sources and other surface clocks, may be understood in a fully quantitative manner.