title: Nitric oxide assisted C60 secondary ion mass spectrometry for molecular depth profiling of polyelectrolyte multilayers.
abstract: BACKGROUND
  Secondary ion mass spectrometry (SIMS) with polyatomic primary ions provides a successful tool for molecular depth profiling of polymer systems, relevant in many technological applications. Widespread C60 sources, however, cause in some polymers extensive damage with loss of molecular information along depth. We study a method, based on the use of a radical scavenger, for inhibiting ion-beam-induced reactions causing sample damage.
  
  
  METHODS
  Layered polystyrene sulfonate and polyacrylic acid based polyelectrolyte films, behaving differently towards C60 beam-induced damage, were selected and prepared as model systems. They were depth profiled by means of time-of-flight (TOF)-SIMS in dual beam mode, using fullerene ions for sputtering. Nitric oxide was introduced into the analysis chamber as a radical scavenger. The effect of sample cooling combined with NO-dosing on the quality of depth profiles was explored.
  
  
  RESULTS
  NO-dosing during C60-SIMS depth profiling of >1 micrometer-thick multilayered polyelectrolytes allows detection, along depth, of characteristic fragments from systems otherwise damaged by C60 bombardment, and increases sputtering yield by more than one order of magnitude. By contrast, NO has little influence on those layers that are well profiled with C60 alone. Such leveling effect, more pronounced at low temperature, leads to a dramatic improvement of profile quality, with a clear definition of interfaces.
  
  
  CONCLUSIONS
  NO-dosing provides a tool for extending the applicability, in SIMS depth profiling, of the widely spread fullerene ion sources. In view of the acceptable erosion rates on inorganics, obtainable with C60, the method could be of relevance also in connection with the 3D-imaging of hybrid polymer/inorganic systems.
authors.affiliation: Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Zappalà
authors.affiliation: Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Motta
authors.affiliation: Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Tuccitto
authors.affiliation: Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Vitale
authors.affiliation: Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Torrisi
authors.affiliation: Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Licciardello
mesh_terms: D000180:Acrylic Resins / Q000032:analysis*; D004573:Electrolytes / Q000032:analysis; D037741:Fullerenes / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D009569:Nitric Oxide / Q000737:chemistry*; D011137:Polystyrenes / Q000032:analysis*; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods*
chemical_list: D000180:Acrylic Resins; D004573:Electrolytes; D037741:Fullerenes; D007477:Ions; D011137:Polystyrenes; D009569:Nitric Oxide; C006903:carbopol 940; C003321:polystyrene sulfonic acid; C069837:fullerene C60