Electronic and Optical Response of Zirconium Diboride with Intrinsic and Extrinsic Defects

Zirconium diboride (ZrB2) is an ultra-high temperature ceramic that combines metallic and
covalent bonding, high thermal conductivity, and strong chemical stability, making it a promising
material for applications such as pellicles, high-temperature coatings, and optoelectronic devices.
In this thesis, the structural, electronic, and optical properties of pristine and defected ZrB2 were
investigated using density functional theory (DFT).
Pristine ZrB2 was first characterized, with results showing metallic conductivity dominated by
zirconium d states, strong covalent Zr–B bonding, and a plasmon peak at ∼6.5 eV. Intrinsic defects
were then examined: boron vacancies were found to be energetically more favorable (Ef = 3.38 eV)
than zirconium vacancies (Ef = 5.39 eV), consistent with their bonding nature. Extrinsic species
were also studied. Oxygen and hydrogen adsorption were energetically favorable (Ef = −0.54
and −0.43 eV), while nitrogen adsorption was unfavorable. Copper incorporation was found to be
possible on zirconium sites (Ef = −0.57 eV) but unlikely on boron sites.
Optical calculations revealed that both pristine and defected ZrB2 maintain high EUV transparency, with ∼99% transmittance for a 50 nm film. Defects introduced only moderate modifications to the dielectric response: oxygen adsorption caused the strongest effect, shifting the plasmon
peak downward by 0.2–0.3 eV, whereas other defects produced minor changes.
These results confirm the robustness of ZrB2 against common point defects and support its
suitability for high-performance optical and structural applications. They also highlight the importance of defect engineering, especially oxygen control, for optimizing its use in practical environments.