W:Al₂O₃ Nanocomposite Thin Films with Tunable Optical Properties Prepared by Atomic Layer Deposition

Abstract

A systematic alteration in the optical properties of W:Al2O3 nanocomposite films is demonstrated by precisely varying the W cycle percentage (W%) from 0 to 100% in Al2O3 during atomic layer deposition. The direct and indirect band energies of the nanocomposite materials decrease from 5.2 to 4.2 eV and from 3.3 to 1.8 eV, respectively, by increasing the W% from 10 to 40. X-ray absorption spectroscopy reveals that, for W% < 50, W is present in both metallic and suboxide states, whereas, for W% ≥ 50, only metallic W is seen. This transition from dielectric to metallic character at W% ∼ 50 is accompanied by an increase in the electrical and thermal conductivity and the disappearance of a clear band gap in the absorption spectrum. The density of the films increases monotonically from 3.1 g/cm3 for pure Al2O3 to 17.1 g/cm3 for pure W, whereas the surface roughness is greatest for the W% = 50 films. The W:Al2O3 nanocomposite films are thermally stable and show little change in optical properties upon annealing in air at 500 °C. These W:Al2O3 nanocomposite films show promise as selective solar absorption coatings for concentrated solar power applications.

Elucidating the Redox Behavior during Atomic Layer Deposition on Lithium-Ion Battery Cathode Materials

“…We measured the thicknesses of the Al 2 O 3 and AlF 3 films on Si witness coupons which were coated along with the powders using spectroscopic ellipsometry. These thicknesses were found to be 1.10 nm for the ALD Al 2 O 3 and 1.30 nm for the ALD AlF 3 , which are in accordance with the expected growth rate of 1–1.5 Å/cycle for both Al 2 O 3 − and AlF 3 . However, no film growth was observed on the Si-coupons which were only dosed with TMA or HFPy, as expected.…”

Efficient Thermal Management with Selective Metamaterial Absorber for Boosting Photothermal CO2 Hydrogenation under Sunlight

“…On the contrary, the cermet-based materials are regarded as excellent candidates for broadband absorption with simple processing methods. [6,14] Therefore, it is a promising approach to replace the nanopattern layer of the MIM structure with cermet composites, which allows the combined absorption of cermet layer and FP cavity modes. This newly constructed structure is expected to achieve spectrally selective absorption within a relatively thin absorption thickness and thus obtain an elevated local photothermal temperature.…”

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

“…Researchers have also demonstrated the effective use of ALD for the synthesis of doped metal oxides [39][40][41][42] and metal NPs embedded in an oxide matrix. 43,44 In this paper, we report an efficient way of preparing both noble metal (Pt) doped In2O3 thin films as well as In2O3 thin films with embedded Pt NPs, using a supercycle ALD approach. Figure 1 demonstrates the basic principle of the synthesis method.…”

“…The island growth mode in Pt ALD has been widely exploited for the synthesis of well-dispersed noble-metal nanoparticles for applications such as catalysis and gas sensing. Researchers have also demonstrated the effective use of ALD for the synthesis of doped metal oxides − and metal NPs embedded in an oxide matrix. , …”