Photothermal study of RF-plasma polymerized hexamethyldisilazane thin films

Plasma polymerization by RF excited low pressure plasmas is a powerful technique for synthesizing thin films for a wide range of applications such in microelectronics, biomaterials and aeronautical industries. Among these applications plasma polymerized hexamethyldisilazane (HMDSN here in) is a promising material due its biocompatibility, optical and electrical properties. In the present paper, we reported the thermal diffusivity measurements of plasma polymerized HMDSN thin films using the probe beam deflection technique (PBD). The samples are thermally thin and optically transparent, with thicknesses ranging from 170 to 600 nm, difficulting their thermal characterization by other photo-thermal techniques (photoacoustic and pyroelectric). PBD measurements were carried out with a diode (20 mW, λ=640 nm) and a HeNe (0.9 mW, λ=632 nm) laser, used as pump source and probe beam, respectively. The probe beam was focused close to the sample surface and its direction was perpendicular to the pump beam. The transverse PBD in skimming configuration is employed and the deflection signal is analyzed using the phase method for the determination of thermal diffusivity. The results show the decreasing of thermal diffusivity with the decreasing of film thickness. HMDSN film׳s thermal diffusivity values are reported in this paper for the first time being in the range of typical polymeric samples.