Studies of PMMA sintering foils with and without coating by magnetron sputtering Pd

Abstract

Polymethylmethacrylate thin foils were prepared by using physical and chemical processes aimed at changing certain properties. The density and the optical properties were changed obtaining clear and opaque foils. DC magnetron sputtering method was used to cover the foils with thin metallic palladium layers. The high optical absorbent foils were obtained producing microstructured PMMA microbeads with and without thin metallic coatings. Rutherford Backscattering Spectroscopy, optical investigation and microscopy were employed to characterize the prepared foils useful in the field study of laser-matter interaction.

Introduction

The polymers treatment using physical and chemical processes [1] permits to obtain new materials with unique properties concerning their electrical conductivity, chemical solubility, mechanical and optical characteristics, porosity and composition, doping with nanoparticles and microstructures, appearing with unlimited and promising applications in fundamental research and industry [2], [3]. Polymers are low cost and exhibit low density, high resistance to corrosion and high strength to weight ratio. Despite a distinctive dominant property of polymer, i.e. the electrical insulating, the interest in the substitution of semiconductors and metals with polymers motivated researchers to overcome this drawback using many techniques such as plasma treatment enhanced by chemical vapor deposition (CVD) [4], doping with different species and laser ion implantation [5]. A powerful technique, applied to polymers, that has gained much interest over other techniques due its high controllability of process parameters, to synthesize thin film with low impurities, is the magnetron sputtering. Although the modifications of polymers have been widely investigated [6], a new research area is focused on the production of porous materials exhibiting the pore size ranging between tens of micrometers [7] and hundreds of nanometers [8]. Recent studies on polymethylmetacrylate (PMMA) based nanoporous materials [9] report that the reduction of the pore size is responsible for the decreasing of the thermal conductivity as a consequence of both heat conduction transfer decreasing by means of the gas phase (Knudsen effect) and the enhancement of the solid matrix tortuosity [10]. Nowadays, great effort is focused to the realization of high optical absorption materials playing a key role in laser-matter interaction studies [11], [12]. The present work is addressed to investigate the porosity of employed polymeric foils; to evaluate the quality of metallic layers deposited on the polymer and produced by magnetron sputtering as well as their structural characterization; to conduct optical analysis of clear and opaque PMMA films in the optical range from UV to visible and to the IR.