Optical properties of ceramic-like layers obtained by low energy ion beam irradiation of polysiloxane films

Giovanni Marietta, Andras Tóth, Imre Bertoti, Tran Minh Duc, Francoise Sommer, Karpat Ferencz

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Abstract

In the present paper we report on the modifications induced by low energy particle beams (1-5 keV He+, Ar+, N+2, He0, N02 and H02) on the chemical structure, optical properties and surface morphology of silicon-based polymer, polyhydroxy-methyl-siloxane (PHMSO). The in situ XPS analysis shows that ion irradiation induces depletion of C atoms and progressive enrichment of Si and O atoms within the irradiated layers, yielding a ceramic-like SiOxCyHz phase of variable composition. For a given projectile, a steady state composition is reached in any case above the fluence of 1 × 1016 particles/cm2. The most efficient conversion to a ceramic-like layer, with a final composition SiO1.85-1.89C0.3-0.4 Hz, is obtained by using 5 keV He+ beams, while N+2 and Ar+ seem less effective. At variance of this, a dramatic carbon enrichment is observed when the PHMSO films are irradiated with fast neutral particles (FAB treatments). The optical measurements show that in general the beam-converted layers remain practically absorption-less, while the relevant features of the reflectivity spectra (positions of maxima and minima) critically depend upon the type of projectile. Thus, 5 keV He+ ion irradiation induces the shift of the reflectivity maxima to shorter wavelengths (blue shift), while 5 keV N+2 ions induce no shift and irradiation with N2 or H2 neutral beams induce a red shift. The AFM measurements show that also the surface morphology critically depends on the nature of the irradiating particles. Thus, 5 keV He+ irradiation produces films as flat as the original polymer surface, while irradiation with Ar+ (inducing a lower degree of conversion) increases the roughness, N+2 irradiation induces characteristic undulations of the surfaces and FAB treatments induces a much higher surface roughening. The experiments show clearly that both the compositional modifications and the irradiation-induced nanometer scale morphological features critically determine the optical properties of the irradiated materials.

Original languageEnglish
Pages (from-to)684-692
Number of pages9
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Volume141
Issue number1-4
Publication statusPublished - May 1 1998

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Keywords

  • Ion beams
  • Optical properties
  • Polymers
  • Surface treatments

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation

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