Chemical solution deposition of metal-organic precursors have favoured the research and development of thin films of simple and complex oxides such as Pb(Zr,Ti)O3, and Al2O3, up to their industrial application in pyroelectric and capacitor devices. Deposition methods used are spin-on and dip-coating. The advantages of the techniques are:
(i) low cost of equipment and chemicals
(ii) large area deposition
(iii) low crystallisation temperatures
A mist deposition system takes the solution of the different precursors into the gas phase from a single pot in contact with a transducer, unlike MOCVD for which individual temperature controlled bubblers with respective heated gas lines and mass flow controllers are needed. It retains all the advantages above but also has the advantages of:
(i) film thickness control
(ii) deposition above ambient temperatures
(iii) conformal coatings on non planar substrates
The system developed at IMEM uses a transducer to generate from the precursor solution a mist that is injected into the reaction chamber by a transport gas. At high frequencies the mist is very fine and hence more reactive than that would be obtained from lower frequency transducers.
The prototype system has been at low cost because of its simplicity and materials used.
The particular advantages of this apparatus are:
(i) efficient coupling between transducer and metal-organic solution
(ii) protection of the transducer from corrosion by the solution and cleaning
(iii) easily applicable to other compositions or reaction configurations.
Further added value comes from the know how to synthesise of solutions that can generate a mist.