Nonuniform Composition Profiles in Amorphous Multimetal Oxide Thin Films Deposited from Aqueous Solution.

Abstract

Metal oxide thin films are ubiquitous in technological applications. Often, multiple metal components are used to achieve desired film properties for specific functions. Solution deposition offers an attractive route for producing these multimetal oxides because it allows for careful control of film composition through the manipulation of precursor stoichiometry. Although it has been generally assumed that homogeneous precursor solutions yield homogeneous thin films, we recently reported evidence of nonuniform electron density profiles in aqueous-deposited films. Herein, we show that nonuniform electron densities in lanthanum zirconium oxide (LZO) thin films are the result of inhomogeneous distributions of metal components. Specifically, La aggregates at the film surface, whereas Zr is relatively evenly distributed throughout single-layer films. This inhomogeneous metal distribution persists in stacked multilayer films, resulting in La-rich interfaces between the sequentially deposited layers. Testing of metal-insulator-semiconductor devices fabricated from single and multilayer LZO films shows that multilayer films have higher dielectric constants, indicating that La-rich interfaces in multilayer films do not detrimentally impact film properties. We attribute the enhanced dielectric properties of multilayer films to greater condensation and densification relative to single-layer films, and these results suggest that multilayer films may be preferred for device applications despite the presence of layering artifacts.