Showing papers by "Brian Wynne published in 2022"

Defect engineering of silicon with ion pulses from laser acceleration

Abstract: Abstract Defect engineering is foundational to classical electronic device development and for emerging quantum devices. Here, we report on defect engineering of silicon with ion pulses from a laser accelerator in the laser intensity range of 10 19 W cm −2 and ion flux levels of up to 10 22 ions cm −2 s −1 , about five orders of magnitude higher than conventional ion implanters. Low energy ions from plasma expansion of the laser-foil target are implanted near the surface and then diffuse into silicon samples locally pre-heated by high energy ions from the same laser-ion pulse. Silicon crystals exfoliate in the areas of highest energy deposition. Color centers, predominantly W and G-centers, form directly in response to ion pulses without a subsequent annealing step. We find that the linewidth of G-centers increases with high ion flux faster than the linewidth of W-centers, consistent with density functional theory calculations of their electronic structure. Intense ion pulses from a laser-accelerator drive materials far from equilibrium and enable direct local defect engineering and high flux doping of semiconductors.

On minimum proper essential extensions in a category

Abstract: Abstract In a concrete category A satisfying certain natural conditions, we investigate minimum proper essential extenstions (A-mpee’s) and how this relates to atoms in the complete lattice hoA of hull operators on A (if A # is the category with objects the A-objects but morphisms just the essential extensions in A, then hoA consists exactly of the reflections in A # ). A further hypothesis inserts itself: We call an A-mpee µ strong just in case the domain and codomain of µ are not isomorphic; [S] is the assumption that every A-mpee is strong. We show (1) if µ is strong, then an atom of hoA is determined by µ, and (2) if [S], then every id ≠ h ∈ hoA lies above an atom and every atom is determined by an A-mpee µ. Examples are presented in various categories of lattice-ordered groups.