Chemical and Structural Configuration of Pt-Doped Metal Oxide Thin Films Prepared by Atomic Layer Deposition

Abstract

Pt doped semiconducting metal oxides and Pt metal clusters embedded in an oxide matrix are of interest for applications such as catalysis and gas sensing, energy storage and memory devices. Accurate tuning of the dopant level is crucial for adjusting the properties of these materials. Here, a novel atomic layer deposition (ALD) based method for doping Pt into In2O3 in specific, and metals in metal oxides in general, is demonstrated. This approach combines alternating exposures of Pt and In2O3 ALD processes in a single 'supercycle', followed by supercycle repetition leading to multilayered nanocomposites. The atomic level control of ALD and its conformal nature make the method suitable for accurate dopant control even on high surface area supports. Oxidation state, local structural environment and crystalline phase of the embedded Pt dopants were obtained by means of X-ray characterization methods and high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). In addition, this approach allows characterization of the nucleation stages of metal ALD processes, by stacking those states multiple times in an oxide matrix. Regardless of experimental conditions, a few Pt ALD cycles leads to the formation of oxidized Pt species due to their highly dispersed nature, as proven by X-ray absorption spectroscopy (XAS). Grazing-incidence small-angle X-ray scattering (GISAXS) and highresolution scanning transmission electron microscopy, combined with energy dispersive X-ray spectroscopy (HR-STEM/EDXS) show that Pt is evenly distributed in the In2O3 metal oxide matrix without the formation of clusters. For a larger number of Pt ALD cycles, typ. > 10, the oxidation state gradually evolves towards fully metallic, and metallic Pt clusters are obtained within the In2O3 metal oxide matrix. This work reveals how tuning of the ALD supercycle approach for Pt doping allows controlled engineering of the Pt compositional and structural configuration within a metal oxide matrix.

Surface mobility and impact of precursor dosing during atomic layer deposition of platinum:in situmonitoring of nucleation and island growth

“…58 Besides monitoring the thin film growth, it is also possible to monitor the behaviour of a deposited film under several conditions, for example, sintering of Pt nanoparticles during annealing in different oxidizing atmospheres, 59 or the formation of bimetallic nanoparticles by annealing ALD deposited layers. 60 A few reports presented ex situ 26,27,[61][62][63] or in situ 12 GISAXS measurements during Pt ALD. In 2009, Christensen et al, investigated the morphology of Pt nanoparticles grown by 10, 20, 30 and 40 ALD cycles on SrTiO 3 surfaces.…”

Rational Component and Structure Design of Noble‐Metal Composites for Optical and Catalytic Applications

“…[ 209 ] A Pt‐doped In 2 O 3 matrix with adjustable thickness and Pt content was also developed by changing the ALD cycles. [ 210 ] At the same time, the loading and composition of the deposited nanoparticles can also be adjusted by changing the deposition temperature of ALD. Elam and co‐workers have developed core–shell Pt–Pd bimetallic nanoparticles with different compositions, [ 202 ] such as Pd 1 Pt 0.5 (1 wt% Pd, 1 wt% Pt), Pt 0.5 Pd 1 (1 wt% Pd, 1 wt% Pt), Pd 1 Pt 1 (1 wt% Pd, 2 wt% Pt), and Pd 1 Pt 1.5 (1 wt% Pd, 2.5 wt% Pt), by varying the deposition temperature of ALD from 100 to 300 °C.…”

ALD Pt nanoparticles and thin-film coatings enhancing the stability and performance of silicon photocathodes for solar water splitting

“…Note that we have implicitly assumed that the growth per cycle on the Pt nanoparticles does not deviate from the steady growth per cycle, however, the deposited amount of SiO2 per ALD cycle may deviate during the initial ALD cycles on Pt due to nucleation effects. 38,39 Hence, the indicated film thicknesses should be regarded as estimates and not as precise values of the actual thicknesses, especially for the samples which received only a few ALD cycles. Further characterization (e.g.…”