Increasing permittivity in HfZrO thin films by surface manipulation

We report on the electrical and physical characterization of nanoscale crystalline HfxZr1−xO2 films by x-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Increasing the ZrO2 content generally led to an increase in tetragonal phase fraction and dielectric constant. This was reflected in both XRD and ATR-FTIR measurements. We demonstrate that not only the composition, but also the distribution of ZrO2 throughout the film determines phase formation. Concentrating ZrO2 at the top surface of the film allowed the dielectric constant to be optimized for a given composition. These observations are explained by a surface energy thermodynamic model.