Department of Physics
Condensed Matter Seminar

The modification of heterogeneous surfaces during particle and plasma irradiation requires an understanding of elemental, chemical and structural evolution at the nanoscale. This is particularly important for systems exposed to high-intensity low-energy irradiation such as plasma-facing components in fusion energy experimental nuclear reactors and plasma-facing mirrors used in nanolithography. In extreme UV lithography sources hyperthermal (50-1000 eV) Sn ions are an ultra-shallow implant in Ru thin-film mirrors penetrating a few nanometers and subsequently diffusing to sublayers below the air/film interface. The implanted species directly affect the EUV optical reflective properties of the mirror at wavelengths that approach the implantation zone. This is particularly important in advanced microlithography applications. At Argonne, Prof. Allain designed and built the IMPACT (Interaction of Materials with Particles and Components Testing) experimental facility designed to study In-situ nanoscale characterization of particle-induced growth and synthesis of surface or low-dimensional state systems tailored during energetic or thermal particle exposure. Surface-sensitive techniques include: low-energy ion scattering spectroscopy (LEISS) with simultaneous forward and backward scattering modes, direct recoil spectroscopy (to study impurity levels in the nanostructure), angle-resolved X-ray photoelectron spectroscopy, and extreme ultraviolet photoelectron spectroscopy (EUPS). Several examples include monitoring the evolution of deposited and implanted Sn on Ru collector mirrors and its effect on mirror EUV reflectivity performance. In addition, Prof. Allain currently leads a collaborative group with Princeton Plasma Physics Laboratory understanding the use of lithium-based surfaces for fusion applications. This talk will focus on the limits and challenges that face in-situ characterization studies of thin-film systems at the nanoscale aided by some examples. The talk will also highlight additional complementary surface-sensitive techniques in a new novel facility being built at Purdue.