Ion irradiation effects on surface mechanical behavior and shrinkage of hybrid sol-gel derived silicate thin films

A study of the effects of ion irradiation on the surface mechanical behavior and shrinkage of organic/inorganic modified silicate thin films was performed. The films were synthesized by sol-gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. The sol viscosity and the spin velocity were adjusted so that the films produced had a final thickness ranging from 580 to 710 nm after heat treatment. The ion species and incident energies used were selected such that the projected ion range was greater than the film thickness, resulting in fully irradiated films. After heat treatment at 300 °C for 10 min, the films were irradiated with 125 keV H⁺, 250 keV N²⁺ and 2 MeV Cu⁺ ions with fluences ranging from 1 × 10¹⁴ to 1 × 10¹⁶ ions/cm². Both hardness and reduced elastic modulus were seen to exhibit a monotonic increase with fluence for all three ion species. Also, H loss was found to increase monotonically with increase in fluence, while the film thickness was found to decrease with increase in fluence.