Physico-chemical properties of plasma-polymerized tetravinylsilane

abstract

English

Plasma-Enhanced Chemical Vapor Deposition (PE CVD) is a suitable technique for preparation of thin films on a basis of organosilicones [1,2]. The technique enables reproducible deposition of plasma polymer films with desired physico-chemical properties [3] by changing the deposition conditions (power, monomer flow rate, pressure). We found out [4] that the elastic modulus of plasma-polymerized (pp-) VTES film can be controlled by the effective power using vinyltriethoxysilane (VTES), a monomer including the functional group - vinyl. However, the double bond in vinyl group was split during the plasma process even if a very low power was used and thus plasma polymer was deficient of vinyl species. Tetravinylsilane (TVS) was used as a monomer for deposition of pp-TVS films for the first time. The symmetric molecule was tested in order to observe an influence of deposition conditions on the vinyl content in pp-TVS films during our study. The helical coupling system [5] was applied to deposit single films using an RF glow discharge operated in pulsed mode. The plasma was monitored by mass spectroscopy and photodiode with respect to the duty cycle (0.001 - 0.5) and period (2 - 1000 ms) of pulsed regime, monomer flow rate (0.05 - 0.62 sccm), pressure (0.1 - 4.4 Pa), and effective power (0.05 - 25 W). Pp-TVS films were analyzed by microscopic and spectroscopic techniques extensively to evaluate surface morphology (AFM), elemental composition and chemical structure (RBS, ERDA, FTIR). A phase-modulated spectroscopic ellipsometer was employed to determine the film thickness (mean deposition rate) and optical constants (refractive index, extinction coefficient) of deposited films. Nanoindentation measurements enabled us to evaluate the elastic modulus and hardness of films prepared at different power. The results revealed that an organic/inorganic character (C/Si ratio was ranging from 4.4 to 8.4) of pp-TVS films and a content of vinyl groups could be controlled by deposition conditions precisely. The elastic modulus and hardness could be varied from 14 to 40 GPa and from 1.6 to 6.4 GPa for power increased, respectively. Absorption of films in ultraviolet region increased with the power as well.

Nano-indentation; Atomic force microscopy (AFM); Ellipsometry; Infrared spectroscopy; Rutherford backscattering spectroscopy; [PACVD

ČECH, V., PEŘINA, V., CONTE, N., STUDÝNKA, J.

12. 9. 2005

Qingdao, Čína

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