This study examined the structural evolution of ultrathin ${\text{Hf}}_{1-x}{\text{Zr}}_x{\text{O}}_2$ composite films with various mixing ratios $\left(x=0,0.1,0.3,0.5,0.7,0.9,1\right)$ prepared by atomic layer deposition using x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and x-ray absorption fine structure (XAFS) analysis. As the relative Zr concentration $\left(x\right)$ was increased, the composite films underwent a martensitic transition from monoclinic to tetragonal crystal structures near $x=0.5–0.7$. $\text{Zr}K$- and $\text{Hf}{L}_3$-edge XAFS revealed a change in the local structures near the Zr and Hf atoms with changes in the crystal structure. At a low Zr content $\left(x\le 0.5\right)$, the next-nearest-neighbor coordination in the monoclinic $\left(m\right)$ local structure showed significant structural disorder due to diverse structural reconstruction from the tetragonal $\left(t\right)$ local structure. Combined XPS and $\text{O}K$-edge XAS studies revealed a decrease in the conduction-band (CB) edge energy with increasing $x$, whereas the valence-band edge energies were invariant. The evolution in the CB structures was analyzed using the concept of metal-ion crystal fields in the $t$ and $m$ cluster models.

• Received 14 June 2010

DOI:https://doi.org/10.1103/PhysRevB.82.094104