Optimizing Vanadium Pentoxide Thin Films and Multilayers from Dip-Coated Nanofluid Precursors

Abstract

Using an alkoxide-based precursor, a strategy for producing highly uniform thin films and multilayers of V2O5 is demonstrated using dip coating. Defect-free and smooth films of V2O5 on different surfaces can be deposited from liquid precursors. We show how pinholes are formed due to heterogeneous nucleation during hydrolysis as the precursor forms a nanofluid. Using knowledge of instability formation often found in composite nanofluid films and the influence of cluster formation on the stability of these films, we show how polymer-precursor mixtures provide optimum uniformity and very low surface roughness in amorphous V2O5 and also orthorhombic V2O5 after crystallization by heating. Pinhole and roughness instability formation during the liquid stage of the nanofluid on gold and ITO substrates is suppressed giving a uniform coating. Practically, understanding evolution pathways that involve dewetting processes, nucleation, decomposition, or hydrolysis in complex nanofluids provides a route for improved uniformity of thin films. The method could be extended to improve the consistency in sequential or iterative multilayer deposits of a range of liquid precursors for functional materials and coatings.

Effect of Annealing on the Development of Fully Transparent Ternary V-O-Na-Si Mixed Metal Oxide Thin Films from Polymer-Assisted Dip-Coated V2O5

“…This also coincides with the observation that the V 2 O 5 -PEG AFM surface images show a higher concentration of crystalline grains than the V 2 O 5 -H 2 O thin films owing to the complexation of the vanadium alkoxide precursor with PEG and the ability of the more viscous precursor to coat the substrate and avoid further roughness development during hydrolysis to V 2 O 5 . 19 Additionally, the rms roughness of the V 2 O 5 -PEG thin films did not vary substantially after 6 h of annealing, where the phase conversion process is incomplete and some patchy areas of the film begin to show optical clearing to a transparent film. These results show that the PAD processes in the PEG-based films allow for smoother surface morphology upon initial deposition, and allow the film to maintain a lower degree of rms roughness during the phase conversion process to a completely transparent thin film for each annealing temperature and time investigated.…”

“…The as-deposited V 2 O 5 is formed as amorphous nanoscale flakes of stoichiometric V 2 O 5 during hydrolysis of the liquid precursor and sets into a thin film form, as previously reported in dedicated electron microscopy analysis. 19,40 These amorphous flakes do not show a defined Raman spectrum until they are crystallized during annealing to form orthorhombic V 2 O 5 as seen in Fig. 4a.…”

“…During the deposition of the thin films, it was shown previously how the formation of the amorphous flakes could be influenced by dewetting characteristics usually found in metal-polymer mixtures. 19,[44][45][46] The application of the PAD technique results in the formation of smaller amorphous flakes with the added benefit of retarding the dewetting mechanism, resulting in a smoother surface with less surface discontinuities. 40 An XPS measurement of an as-deposited thin film of V 2 O 5 on a glass substrate was performed as shown in Fig.…”

“…With an increasing range of potential applications, the importance of rapid thin film deposition over large areas is of greater importance, with solution processed techniques a strong candidate to fill this technological need. 19,20 * Electrochemical Society Student Member. * * Electrochemical Society Active Member.…”

Solution processed ZnO homogeneous quasisuperlattice materials

“…25 Solution processing offers a method of coating a wide range of substrate shapes to enable new applications as channel materials in flexible, wearable, and plastic electronics. 26 Solution processed deposition techniques employ liquid-based precursors to create films and nanostructures by spin-coating, 27 dipcoating, 28 ink-jet printing, and gravure printing. 29 Liquid precursor solutions can be alkoxides, nitrates, and carboxylates, 30 or other more complex inorganic-organic species.…”