Kudos to Shelby Fields, University of Virginia Ph.D. student of materials science and engineering, who first-authored a collaborative research paper published and selected as an “editor's pick” in Applied Physics Letters.The paper, Compositional and phase dependence of elastic modulus of crystalline and amorphous Hf1-xZrxO2 thin films, showcases a method to directly measure the speed of sound within a nanoscale thickness thin film to quantify a material property called the elastic modulus. This value is critical for measuring the stress present within materials following their processing.
Fields is advised by Jon Ihlefeld, associate professor of materials science and engineering and electrical and computer engineering. The research involved members of Ihlefeld's multifunctional thin film group; professor of mechanical and aerospace engineering Patrick Hopkins and recent PhD graduate David Olson working in Hopkins' ExSiTE Lab; Diane A. Dickie, senior scientist in UVA's Nanoscale Materials Characterization Facility; and researchers at the Sandia and Oak Ridge National Laboratories.
The team applied their direct measurement method to hafnium zirconium oxide thin films, enabling future investigations of stress effects on the stability and performance of the material system. These silicon-compatible materials, which demonstrate ferroelectric properties when processed at < 40 nm thickness scales, are being developed for next-generation computer chip transistor and memory technologies.
The team's femto-second laser-based technique directly measures the speed of sound through the material, which is historically very difficult in films that are only nanometers thick. Thus, the measured 20 nm-thick hafnium zirconium oxide thin films with varying compositions presented ideal candidates for characterization. To demonstrate the utility of this elastic modulus value, the team utilized X-ray diffraction measurements to quantify the post-processing stress present within each of the films.