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.

Metal Composition and Polyethylenimine Doping Capacity Effects on Semiconducting Metal Oxide–Polymer Blend Charge Transport

“…It is known that when annealing/converting a metal oxide precursor to a MO film in air the uppermost surface of the film is typically denser since direct air exposure facilitates oxidation of the MO precursor and further facilitates film densification by release of gaseous byproducts . Such phenomena were also observed in other solution processed metal oxides. , Higher PEI loadings enhance this effect not only for the third layer but, when present, for the other two layers as well, and is clearly seen for all 3 wt% PEI-doped MO samples (Figure S21).…”

“…66 Such phenomena were also observed in other solution processed metal oxides. 67,68 Higher PEI loadings enhance this effect not only for the third layer but, when present, for the other two layers as well, and is clearly seen for all 3 wt% PEI-doped MO samples (Figure S21).…”

Study of electronic and optical response of Zn-CeO2 using first principle and experimental investigations

“…This led to limited production and low throughput [11,12]. Compared with these vacuum-based deposition techniques, solution processing like the sol-gel method has become a popular method because of its low cost, easy controllability of chemical stoichiometry, low processing temperature, large-scale production, and its ability to produce chemically homogeneous and uniform films over large areas [13].…”

Composition Dependence of Optical Properties and Band Structures in p-Type Ni-Doped CuO Films: Spectroscopic Experiment and First-Principles Calculation

“…Various techniques have been developed to prepare CuO films. Especially, the sol–gel method is a facile and low-cost technique, which can produce uniform films in large area with a precise stoichiometry . Moreover, it is convenient and accurate to regulate and control the doping concentration for the sol–gel process.…”

“…Especially, the sol−gel method is a facile and lowcost technique, which can produce uniform films in large area with a precise stoichiometry. 6 Moreover, it is convenient and accurate to regulate and control the doping concentration for the sol−gel process. To enhance the electrical and optical performance, some transition-metal elements have been used to dope the CuO films.…”