title: Domain dynamics in thin solid films following ultrashort pulse excitation.
abstract: MnAs epilayers grown on GaAs are used as a model system to study the effects of strain and epitaxial constraints on the dynamics of structural domains following 150 fs pulse pumping. Optical diffraction over 7 orders of magnitude of time is used to probe the evolution of the domains that are spatially periodic between 10 and 42 °C because of misfit strain and substrate mediated periodic elastic strain. Following excitation of 150 and 190 nm thick films, the domain fractions and the elastic strain oscillate with an ~400 ps period while the average low temperature phase fraction decreases monotonically for ~2 ns reflecting MnAs heat diffusion. Equilibrium structures are restored in 100 ns-2 μs via substrate heat diffusion. Excitation of transient periodic domains from the homogeneous low temperature phase can occur for temperatures as low as 4 °C but only after ~20 ns during film cooling.
authors.affiliation: Department of Physics and Institute for Optical Sciences, University of Toronto, Toronto M5S1A7, Canada.
authors.forename: Jesse J
authors.initials: JJ
authors.lastname: Dean
authors.forename: David W
authors.initials: DW
authors.lastname: Rench
authors.forename: Nitin
authors.initials: N
authors.lastname: Samarth
authors.forename: Henry M
authors.initials: HM
authors.lastname: van Driel