DOE OSTI2018
We report that nanocomposite coatings, comprised of a precisely blended mixture of components, have diverse applications in microelectronics, optics, sensors, and solid-state detectors. By varying the composition of the mixture, the electrical, optical, and physical properties of the coatings can be “tuned” over almost the full range of the individual components, and can sometimes yield properties distinct from those of any of the constituents. There are many techniques for producing nanocomposite coatings, but atomic layer deposition (ALD) is particularly well suited for controlling the properties of the fabricated coatings. ALD uses alternating cycles of gaseous precursors to a solid surface to deposit materials in an atomic layer-by-layer fashion. Because a chemical reaction on the surface naturally terminates when the surface functional groups are all reacted, the amount of material deposited in one ALD cycle is easily controlled. This self-limiting property, coupled with facile diffusion of the precursor vapors into narrow pores and voids, allows complex, 3-dimensional substrates to be coated with excellent uniformity and conformality. ALD can be used to deposit a wide variety of materials including metal oxides, nitrides, sulfides, and even pure elements. By alternating between two materials (e.g., a metal and a metal oxide), we can synthesize complex nanocomposite coatings. Lastly, the thickness of the coating is controlled by the total number of ALD cycles performed, and the composition is controlled by the ratio of the ALD cycles executed for each of the two components.