skip to main content

Title: Self-assembly of a new type of periodic surface structure in a copolymer by excimer laser irradiation above the ablation threshold

We report self-assembly of periodic surface structures in a commercial block copolymer (BCP) (Filofocon A) upon irradiation with a few tens of excimer laser pulses (20 ns, 193 nm) at fluences above the ablation threshold. This new type of structures is characterized by much larger periods than those characteristic for Laser-Induced Periodic Surface Structures (LIPSS) and features nanochains instead of ripples. We find a period of 790 nm at 400 mJ/cm{sup 2}, scaling linearly with laser fluence up to a maximum of 1.0 μm. While an entangled random network of nanochains is produced for normal-incidence and non-polarized light, nanochain alignment can be achieved either by irradiation at an angle or by using linearly polarized light, forming a lamella-like structure. In both cases, the nanochains are aligned parallel to the penetrating polarization orientation and their period does not show a dependence on the angle of incidence, as opposed to the general behavior of standard LIPSS. Also, our results show that the chains are not formed by frozen capillary waves. In contrast, we show analogies of the nanochains produced to lamellar structures fabricated on a smaller scale in other BCP. We discuss the origin of the self-assembly process in terms of amore » combination of chemical (BCP), optical (surface scattering), and thermal (melting, coarsening, and ablation) effects.« less
Authors:
;  [1] ;  [2]
  1. Instituto de Optica, CSIC, Serrano 121, 28006 Madrid (Spain)
  2. BAM Bundesanstalt für Materialforschung und–prüfung, Unter den Eichen 87, 12205 Berlin (Germany)
Publication Date:
OSTI Identifier:
22217913
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 15; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABLATION; COPOLYMERS; EXCIMER LASERS; INCIDENCE ANGLE; IRRADIATION; MELTING; NANOSTRUCTURES; PERIODICITY; POLARIZATION; PULSES; SCATTERING; SURFACES