Optical properties of La-incorporated HfO2 upon crystallization

Abstract

The imaginary part of the dielectric constant (ε2) and the band gap energy (Eg) of as-deposited and crystallized HfO2 and La-incorporated HfO2 (La–HfO2) are extracted from spectroscopic ellipsometry. As-deposited amorphous HfO2 and La–HfO2 have similar absorption tails, which implies the existence of disorder in the amorphous film structure. Upon crystallization, the absorption tails are reduced and Eg increases for both HfO2 and La–HfO2. But disorder still exists and interband states form in pure HfO2, whereas disorder in crystalline La–HfO2 is largely reduced, which might be the result of La atoms incorporating into the HfO2 host, forming a new HfLaxOy network after crystallization.