From the precursor sols and solutions that are prepared (see precursor chemistry), films can be deposited with thicknesses varying over a wide window, from several hundreds of nm down to a few nm. The chemical solution deposition (CSD) process is carried out by spin-coating or dip-coating followed by thermal treatments in order to prepare thin films. By CSD, most any composition of metal oxide can be deposited as films, by applying the precursor solutions available. A challenge in this research area is the low temperature achievement of the oxide formation, which is crucial for depositions onto flexible substrates such as PET, PEN, etc. that are applied in packaging, flexible electronics, etc. Besides the chemical solution deposition route, hydrothermal film growth is established as well where it is achievable, e.g. for the preparation of ZnO.
Besides continuous, uniform films, numerous applications also require the deposition of nanostructured films or nano-islands. This is achieved by microstructural instability phenomena, basically caused by rupture of the film due to stress during high temperature annealing. However, besides starting from a continuous film to prepare nanodots onto substrates, a more straightforward route is to prepare nanoparticles in dispersion or micellar solutions, followed by deposition of the dispersion. Only one step farther is the preparation of nanocomposite or heterostructured materials, which could be achieved by a combination of the methods explained above.
It is clear that these bottom-up synthesis methods allow to fabrication nanostructured materials from the atomic or molecular building blocks upwards to the solid material. We strive to use simple, bench top methods, with low equipment cost and high material efficiency.