Solution Deposition Precursors
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Introduction
Solution deposition is a way to produce advanced precision films and coatings, also known as the sol-gel method, which is used to prepare various inorganic and hybrid composites from precursor solutions. The process of chemical solution deposition includes:
- Metal alcohol salts and other organic or inorganic metal salts containing a certain percentage of ions are dissolved in a common solvent to form a homogeneous precursor solution by hydrolysis and polymerization.
- The precursor solution is uniformly spin-coated onto the substrate, and a three-dimensional polymeric spatial network gel with the oxide precursor as the backbone is formed by aging and inter-gel polymerization.
- Drying to remove organic matter and increase thickness by repeated coating.
- Annealing to obtain inorganic films with a certain crystalline structure.
Characteristics
The precursor solution occupies an important position throughout the process, and the configuration of the precursor is critical to the performance of the film. For example, although almost all alcohols can be used as solvents, ethylene glycol methyl ether is the most widely used chemical solvent in the preparation of perovskite materials. In the sol-gel step, ethylene glycol monomethyl ether is the optimal choice, and the main reactions for precursor formation are the hydrolysis reaction and the condensation reaction of the alcohol salt reagent. After these two reactions metal-oxygen-metal (M-O-M) bonds are formed. In addition, in the case of fluorine-containing precursors, numerous studies have confirmed that reducing the fluorine content from the conventional perfluorinated precursors is beneficial for reducing the heat treatment time and improving the surface quality of the films. It is also believed that fluorine eventually forms corrosive HF gas with the participation of water vapor, and reducing the fluorine content can reduce the release of HF and thus reduce the negative impact on the film quality. Precursors can also be chemically modified, such as polyvinyl acetate (PVAc) modified PZT (Lead Zirconate Titanate) precursor sol, which can make the PZT film denser, reduce cracking, polymer polyvinylpyrrolidone (PVP) can also achieve this effect.
Application
Precursor solutions are widely used in industrial production due to their ability to precisely control the stoichiometric ratio of film-forming materials and their low cost. For example, the Y2O3 transition layer was prepared on a woven Ni-5%W(N-5W) strip by chemical solution deposition of metal salts using acetic acid note as the raw material to prepare the precursor solution. A good template was provided for the growth of YBa2Cu3O7. At the same time, with the continuous exploration of the synthesis process of precursors, their application fields are expanding, which show a wide range of application prospects in many fields such as optoelectronic devices, efficient catalysts and biological probes.
Reference
- Jiao T J, You C, Tian N, et al. High tunability and low loss via establishing an internal electric field in LiFe5O8/Ba0.6Sr0.4TiO3 composite films using chemical solution deposition method. Applied Surface Science, 590: 153112.