Emergence of Novel Synergetic Optical and Electrical Properties at Near-Equal Ratios for Composition-Tuned Atomic Layer Deposited Pt:TiO₂ Composite Thin Films

Description

Composite thin films have been shown to exhibit unique combinations of electrical, catalytic, and optical properties. However, most studies so far have focused on fully non-metallic inorganic systems (e.g., oxides, nitrides, sulfides) as well as non-metallic inorganic:organic hybrids.[1] In this work, we deposit and study metal:metal-oxide composite thin films using atomic layer deposition (ALD) and evaluate their potential for various applications. Platinium and TiO2 were selected for this purpose due to their catalytic, optical, and electrical properties.

A series of Pt:TiO2 composite thin films were grown from trimethyl methylcyclopentadienyl platinum (IV) (Pt(CpMe)Me3) and O2 cycles for metallic platinum along with titanium chloride (TiCl4) and H2O cycles for TiO2. The resulting films consist of a mixture of metallic Pt and TiO₂, where the study of their electronic and optical properties reveals varying interactions between the two phases depending on their ratios. For cycle ratios equal to or greater than 1:4, the properties are predominantly controlled by the dominant component, with some contribution from the minor component. For example, the 4:1 ratio sample (i.e. 4Pt:1TiO2), is optically reflective and illustrates mostly metallic-like electrical behavior. However, for the samples in the near-equal ratios range (1:1, 2:1, and 1:2) some properties appear as a mixture of both components, while new characteristics also emerge. Notably, samples in this range exhibit p-type semiconductor behavior with low activation energy, high carrier concentration, and high conductivity. Additionally, they are UV-absorbent yet transparent in the visible light range, featuring a wide optical bandgap. Such materials have potential applications in various fields, including transparent electronics, optoelectronics, and photocatalysis.

The elemental purity and oxidation states were verified by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to investigate the film morphologies. The film properties were studied utilizing a series of methods including grazing incidence X-ray diffraction (GI-XRD), X-ray reflectivity (XRR), UV-Vis spectroscopy, and physical properties measurement system (PPMS).

Period	27 May 2025
Event title	European Materials Research Society Spring Meeting
Event type	Conference
Location	Strasbourg, FranceShow on map
Degree of Recognition	International