Depth distribution of silver particulate films deposited in softened polystyrene substrates studied through Rutherford backscattering spectrometry

The depth distribution of silver particulate films deposited on softened polystyrene substrates has been studied through Rutherford backscattering spectrometry (RBS). 150 nm thick silver films were deposited on polystyrene (PS) coated glass substrates held at 455 K and 490 K in a vacuum of 8 × 10^-6Torr. The substrates were irradiated with 8 MeV electrons to a dose of 25 kGy prior to deposition. Ion scattering measurements indicated that the silver particulates are formed at a few tens of nanometers beneath the PS surface for both unirradiated and irradiated substrates. The particulate structure seems to be a two-dimensional array rather than a three-dimensional distribution. The morphology of the particulate structure, the depth of maximum concentration of the particles as well as the width of the distribution seems to depend on the deposition rate and substrate temperature. The electron irradiation of the PS substrate gives rise to the modification of the morphology of the particulate structure due to the induced polymer-metal interaction arising from the free radicals created by the irradiation.