Formation of Fractal Structures from Silicon Dioxide Nanoparticles Synthesized by RF Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition

Abstract

Fractal structures were formed on silicon substrates from SiO2 nanoparticles homogeneously synthesized in low temperature atmospheric pressure plasma from tetraethoxysilane (TEOS). RF discharge (power absorbed was about 10 W) sustained between two parallel mesh electrodes was used to generate plasma. The average size of nanoparticles was in the range of 8-20 nm and was determined by process parameters. The obtained products were analyzed by SEM (scanning electron microscopy) and XPS (X-ray photoelectron spectroscopy). Values of fractal dimension parameter of bidimensionals agglomerates formed on the substrate surface from nanoparticles were calculated with the use of Gwyddion and others. It was found that values of this parameter of the deposited structures varied in the range of 1.48-2 and were determined by combination of the process parameters. An empirical model explaining mechanism of the fractal structures formation and variation of the fractal dimension parameter with the process parameters was proposed.

Experimental study of fractal clusters formation from nanoparticles synthesized by atmospheric pressure plasma-enhanced chemical vapor deposition

“…Synthesized nanoparticles collected on the solid substrate surface. Preliminary results of that study describing fractal structures and the possible explanation of their formation mechanism was presented (Alexandrov 2011;Mishin 2012).…”

Spatial distribution of the electrical potential and ion concentration in the downstream area of atmospheric pressure remote plasma

“…11,17,18 Capacitively coupled plasma (CCP) was generated and sustained in the gap between two plane parallel mesh electrodes (24 mm in diameter) made of stainless steel. The electrodes, separated by 2 mm, were placed perpendicular to the gas flow direction.…”

“…We have previously demonstrated 17,18 the capability of the fractal cluster formation and the regularities of the morphology dynamics of the deposit consisted of SiO 2 nanoparticles during atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) from tetraethoxysilane (TEOS). Using the experimental setup with remote plasma, nanoparticles have been transferred from the syn-thesis area to the substrate by a carrier gas containing a significant amount of ions, which finally leads to the acquisition of electrical charge by nanoparticles.…”

“…Electrical forces, which arise owing to the uneven charge distribution of the deposit surface, can lead to self-organization of nanoparticles and rearrangement of the surface morphology. 17,19 Inhomogeneity of the electric field spatial distribution in the PECVD reaction chamber can be a crucial factor responsible for agglomeration and coalescence of nanoparticles synthesized from the vapor phase. 20,21 Interaction of charged nanoparticles and dipoles with uneven electric fields of plasma can change their velocities and alter spatial allocation.…”

“…the distance between the bottom electrode and the substrate. 11,17,18 The used chamber and electrode design was entirely different from such well studied systems equipped by remote low-temperature plasma and operated under atmospheric pressure as jet systems, [27][28][29] corona discharge systems, [30][31][32] microwave discharge systems. [33][34][35] In the cases of all above mentioned systems, plasma (i) was spatial inhomogeneous and (ii) freely collapsed in the chamber area between the discharge area and the substrate.…”