Spray-layer-by-layer assembly can more rapidly produce optical-quality multistack heterostructures

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Structurally colored thin films offer tunable optical properties.
• Traditional layer-by-layer (LbL) assembly methods can be time-consuming.
• Developing rapid fabrication techniques for complex multilayer heterostructures is crucial.

Purpose of the Study:

• To develop an automated spray-LbL assembly method for fabricating highly reflective thin films.
• To tune the optical properties of thin films for near-UV light wavelengths.
• To compare the efficiency and characteristics of spray-LbL assembly with immersion LbL assembly.

Main Methods:

• Utilized automated spray-layer-by-layer (LbL) assembly with alternating high (TiO(2)) and low (SiO(2)) refractive index nanoparticles.
• Employed a non-quarter-wave design for fabricating multilayer heterostructures.
• Characterized thin films using ellipsometry, atomic force microscopy (AFM), UV-vis spectroscopy, and transmission electron microscopy (TEM).

Main Results:

• Achieved highly reflective (∼90%) structurally colored thin films with tunable reflectance peaks at near-UV wavelengths.
• Spray-assembled films exhibited comparable roughness and refractive index to immersion-assembled Bragg stacks.
• Fabrication time was significantly reduced, with a bilayer deposition time of approximately 90 seconds compared to 36 minutes for immersion LbL.

Conclusions:

• Automated spray-LbL assembly is a rapid and effective method for producing advanced optical thin films.
• Spray deposition time is a key parameter for controlling film thickness, optical properties, and uniformity.
• This technique provides a faster route to complex multilayer heterostructures with high reflectance.