We report on the electrical and physical characterization of nanoscale crystalline HfxZr1-x O2films by x-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Increasing the ZrO2content 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 ZrO2throughout the film determines phase formation. Concentrating ZrO2at 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. © 2009 American Institute of Physics.