Nanolaminates with Novel Properties Fabricated Using Atomic Layer Deposition Techniques

摘要

This AFOSR grant worked on the development, understanding and applications of atomic layer deposition (ALD) for nanolaminates. ALD can be used to fabricate unique nanolaminates with novel properties. Nanolaminates are multilayered thin film structures with nanometer dimensions and very high interfacial density. These multilayer structures can display novel properties that are not simply a 'rule of mixtures'. These special properties can be optimized by manipulating the thickness and composition of the individual nanolayers. The optimized nanolaminates may have important applications as better protective thermal barrier coatings and enhanced superlattice Bragg reflectors in the x-ray region. During the course of this research, the growth and characterization of W/Al2O3 nanolaminates was examined as a model system. The W/Al2O3 nanolaminate has revealed many fascinating thermal and optical properties. Very low thermal conductivity W/Al2O3 nanolaminates were demonstrated that displayed thermal conductivities less than yttria-stabilized ZrO2. Extremely high x-ray reflectivities were also observed for w/Al2O3 nanolaminates. In particular, world record x-ray reflectivities were observed in the hard x-ray region. The quality of the W/Al2O3 nanolaminate is dependent on the nucleation and growth of the W and Al203 nanolayers. Consequently, detailed experimental measurements and theoretical simulations have explored W ALD surface chemistry and the nucleation of W ALD on Al2O3. The project has aimed to establish correlations between thermal and optical properties and nanolaminate structure, interfacial density and composition.