Solid-state NMR Study of Amorphous Aluminum Oxy-Hydroxide Thin Films

Aluminum is an ideal metal for solution-processed oxide dielectrics because it can form polymerized hydroxo networks in aqueous solution and dense amorphous oxide dielectrics by vacuum methods. Atomic layer deposition (ALD) is the traditional vacuum method for thin film deposition, however, ALD is not the most economically feasible method for fabrication due to the high operational cost and limitations in large surface-area applications.¹ Solution deposition is a more economical deposition method which is more cost-saving and ideal for large surface area thin film fabrication.² The behavior of the solution-solid structural conversion remains an enigma thus the project seeks to understand the thin film transformation from solution to solid in order to fabricate films with optimal properties.¹

Aluminum oxide (Al_xO_y) thin films prepared from aqueous solution-deposited cluster precursors have been proposed for use in devices such as high-k dielectricsin solar cell materials.¹The films are fabricated with two different tridecameric hydrooxo aluminum precursors, spin-coated on a substrate and annealed to high temperatures. The low temperature range of these films are amorphous and lack long range order which complicates the analysis by traditional means; however, solid-state nuclear magnetic resonance (ssNMR) can be used to determine the amorphous structure of these materials. Herein, a combination of x-ray diffraction (XRD), and NMR techniques are used to elucidate the phase transformation of these thin films as they are annealed to high temperatures.