Tunable Electrical and Optical Properties in Atomic Layer Deposited TiO2:Pt Thin Films via Dynamic Metallic Nanoparticle Formation

Composite TiO2:Pt thin films deposited by atomic layer deposition (ALD) exhibit significant temperature‑dependent resistivity transitions, from insulating to semiconducting to metallic‑like conducting behavior, while remaining transparent to visible light and strongly absorbing ultraviolet (UV) radiation. The composite films are fabricated using a supercycle approach, and the morphological, electrical, and optical properties are systematically investigated for a series of films with the cycle ratio varying from 4TiO₂:1Pt to 1TiO₂:4Pt. The thus deposited thin films, specifically those with 2TiO₂:1Pt, 1TiO₂:1Pt, and 1TiO₂:2Pt ratios, consist of metallic Pt nanoparticles embedded within the anatase-type TiO₂ matrix, in which the optical properties are primarily governed by the TiO₂ component, whereas the electrical behavior depends on the Pt particle size and density. Notably, films with a 2TiO₂:1Pt ratio undergo morphological alterations due to the nucleation of Pt nanoparticles beginning at temperatures slightly above room temperature (≈340 K), resulting in alterations in the electrical resistivity. These findings highlight the potential of ALD-grown TiO₂:Pt composite thin films for applications in transparent electronics, optoelectronics, and photocatalytic systems.