2:00 PM TODAY! AMO Seminar Ben Torralva, U.Mich. in 4136 2:00-3:00, Thur. Nov. 17

[Finnell, Jenny]

Please join us at 2:00PM today, for an AMO Seminar presented by Ben Torralva, University of Michigan, in 4138, hosted by Enam Chowdhury.
Abstract and Bio are below.

Thanks,
 Jenny Finnell
Physics Dept | Ohio State University | 191 W. Woodruff Ave, Columbus, OH 43210
finnell.2 at osu.edu<mailto:finnell.2 at osu.edu> | Office 1: 4142, 292-4775 | Office 2: M2031, 292-2403 (2:00-4:00PM)

Ultrafast laser driven self-assembly of GaAs surface structures

Ben Torralva

Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, Michigan 48109


Abstract

The interaction between multiple intense ultrashort laser pulses and solids universally produces a regular nanoscale surface corrugation. A coupled mechanism has been identified that operates in a specific range of fluences in GaAs between the band-gap closure and ultrafast melt thresholds that produces a unique corrugation known as high spatial frequency laser induced periodic surface structures (HSFL). The structures have widths of ~100 nm, crest to trough heights of ~400 nm, and are predominately epitaxial single crystal. HSFL self-assembly is initiated when the intense laser field softens the interatomic binding potential, which leads to an ultrafast generation of point defects. The morphological evolution begins as self-interstitial diffusion, driven by stress relaxation, to the surface producing 1-2 nm tall islands. The interplay between surface plasmon polaritons, that localize defect generation within the structures present on the previous laser exposure along with stress relaxation driven defect diffusion, results in the evolution of the surface through three periodic morphologies with periods of 165 nm, 355 nm, and a final period of 180 nm. Experimental and theoretical results will be presented to give a complete picture of HSFL formation with an emphasis on the quantum molecular dynamics and finite element frequency domain simulations used to develop our model.


Bio: Ben Torralva is an assistant research scientist in the Climate and Space Sciences and Engineering department and the Center for Ultrafast Optics at the University of Michigan.  After receiving his Ph.D. in physics under Roland Allen at Texas A&M University, he did a postdoc with Patrice Turchi at Lawrence Livermore National Laboratory and later became a staff scientist there.  At the University of Michigan, he uses and develops quantum molecular dynamics and continuum models to study laser-matter interactions.

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