Transparent and scratch-resistant zirconium oxide thin films were deposited in radio-frequency plasma-enhanced chemical vapor deposition process on glass and polycarbonate substrates using zirconium-
tetra-tert
-butoxide, [Zr(O
t
Bu)
4
], as the precursor. Investigations on film morphology (AFM), thickness (cross-sectional SEM), phase structure (X-ray diffraction), chemical composition (X-ray photoelectron spectroscopy), and optical properties (UV/Vis, ellipsometry) revealed the interplay of process parameters (plasma power, gas composition, deposition time, and precursor flux) on the composition and properties of the coatings. High-quality transparent coatings (90%) with a tunable refractive index (
n
=1.7-2.1) and abrasion-resistant properties were deposited on both polymer and glass substrates. Despite low deposition temperatures (100°C), the coatings showed good adherence to the substrate and extraordinary barrier properties that were further improved by depositing intermediary SiO
x
-layers. Phase analysis of the predominantly amorphous films showed the incipient crystallization of ZrO
2
.