Paper PS1-WeA10
Gas-phase Diagnostics for Understanding Plasma Processing to Tailor the Surfaces of Inorganic Thin Films and Nanoparticles

Wednesday, October 20, 2010, 5:00 pm, Room Aztec

Plasma-enhanced chemical vapor deposition (PECVD), plasma etching, and plasma modification of surfaces are emerging as important tools in the development of biomaterials, hard coatings and other diverse applications. Recently, we have explored the use of both low-pressure rf plasmas as well as atmospheric plasmas to specifically tailor the surface properties of a variety of inorganic materials with a range of morphologies from flat substrates to membranes and nanoparticle systems. Despite the broad range of applicability of plasma processing for producing materials with specific surface properties (e.g. hydrophilicity, chemical functionality, etc.), many mechanistic details remain unknown. Understanding the contributions of gas-phase species is critical to understanding the chemistry that leads to specific surface modifications. In addition, the surface interactions of gas-phase plasma species provide critical molecular level information about plasma processing, especially at interfaces. In addition, power dissipation and energetics are also important for elucidation of mechanistic details in plasmas. The imaging of radicals interacting with surfaces (IRIS) technique uses laser-induced fluorescence (LIF) to provide spatially-resolved images of plasma species. Furthermore, IRIS provides direct information on the energetics of plasma-generated radicals as well as for species scattering off of surfaces. Combined with quantitative optical emission spectroscopy (OES) data, we have measured the internal and translational temperatures for a range of species in a variety of plasma environments. This work concentrates on OH radicals in H₂O plasmas used to create hydrophilic metal oxide surfaces, CH radicals in plasma polymerization systems for nanocomposite materials, and, SO₂ and CF_x species in dielectric etching systems. For many of these molecules, vibrational temperatures are significantly higher than rotational temperatures and the partitioning of energy is correlated to surface reactivity. Comparison between atmospheric and low temperature plasmas as well as flat vs. nanostructured substrates will be made. Preliminary results from computational models of our plasma systems will also be presented. The gas-phase data are complemented by a range of surface and materials analysis data that reveal a more detailed picture of the overall plasma process in each system.