Growth and Analysis of Titanium Dioxide Dusty Microparticle In Capacitively Coupled RF-Plasmas

Particles can spontaneously grow from reactive gases in a plasma to form dust. Over the past few years, several studies have focused on the growth of hydrocarbons and silicates from reactive gases such as acetylene and silane in argon plasmas. Here, we report for the first time the growth of titanium dioxide
$(\text{TiO}_{2})$
dusty microparticles in a capacitively coupled rf plasma. The particles are spherical and grow up to a maximum diameter of 500 nm. The particle growth is cyclic. When they reach a critical radius, gravity becomes the dominant force on the particles and the particles fall out of the plasma. The collected particles are imaged via optical microscopy. The as-grown particles are amorphous. However, when air annealed at
$500^{\circ}\mathrm{C}$
, they crystalize into anatase and gradually transform into rutile when annealed at higher temperature. X-ray diffraction and Raman spectroscopy are used to characterize the crystalline and chemical properties of the particles. We discovered that the base pressure of the particle growth chamber affects the morphology, size, cycle time, and temperature required for crystallization. We will present results for
$\text{TiO}_{2}$
growth with base pressure varying from 1 - 10 millitorr. This presentation will discuss the evolution of the particle morphology as a function of particle growth time and plasma conditions. We will also show that gas “contamination” (i.e., initiating particle growth at a high initial base pressure), strongly influences the final structure of the titanium dioxide particles after annealing. The experiments and results presented here will pave the way for studies on new materials growth, besides hydrocarbons and silicates, in a dusty plasma.