New developments and applications in sol-gel coatings

In this overview we describe some recent developments of technological interest realized at INM in the processing of sol-gel coatings. Nanoscale crystalline particles, fully redispersed in aqueous solutions, have been developed to produce thin ceramic layers at low temperature. As an example, antistatic optical coatings and conducting membranes based on SnO2:Sb material are reported. New wet chemical processes have been developed to extend the sol-gel basic principles for the coating of oxide compounds on plastic (biomimetic process) and sulfide materials (MoS2). Also ink-jet and pad printing processes, well established in other fields, have been adapted for the development of micro structured coatings. As examples, the realization of single and arrays of spherical and cylindrical refractive microlenses is presented. Finally non conventional sintering process using high power CO2 laser is exemplified for the obtention of optical quality transparent conducting coatings under high sintering rate (30 cm2/s)

Non-luminescent disexcitation of F-center pairs by exchange-softened vibrational modes

The non-luminescent and spin-dependent disexcitation process observed in F-center pairs in alkali halides at low temperature is explained by a covalent bond within the pair. Exchange effects give a negative contribution to the lattice potential energy. If the pair separataion is small, local modes become unstable and spontaneous lattice distortions bring back the pair in its ground state

Transparent conducting films in the Zn-Sn-O tie line

Coatings were obtained on borosilicate glass and fused silica substrates with thicknesses of up to 230 nm from solutions with compositions along the Zn-Sn-O tie line. The preparation of the sols was accomplished by combinatorial chemistry with a robotic sample processor using different Zn-II, Sn-II and Sn-IV salts and alkoxides, as well as salts of different doping agents ( e. g. Sb-V, Ta-V, In-III) dissolved in various solvents and additives. The films were made by spin- coating followed by a thermal treatment in air, inert or reducing atmosphere at temperatures up to 1000°C. Except for a few cases, mixed crystalline phases of ZnO, SnO2 and ZnSnO3 or Zn2SnO4 are usually observed within the range 0.4 < [Zn]/([ Zn] + [ Sn]) < 0.75. Pure Zn2SnO4 and ZnSnO3 coatings exhibit good optical properties with a haze < 0.2% and a transmission in the visible range > 85%. In contrast to literature, results obtained for similar coatings by sputtering and pulsed laser deposition, all the sol - gel coatings showed a high resistivity of rho > 3 &Omega;cm even after a forming gas treatment and/ or doping

Modeling of optical and electrical properties of In2O3:Sn coatings made by various techniques

The optical and electrical properties of two types of wet chemical processed tin doped indium oxide (ITO) films deposited by spin coating technique as well as of a commercial sputtered ITO film have been measured. The transmission and reflection spectra in the wavelength range 0.25 to 20 µm have been simulated using the Scout 2 software with different dielectric function models. The electrical parameters obtained from the modeling are compared with those obtained experimentally. The optical data of a low porosity (28%), low specific resistivity (? = 6.

Liquid film deposition of chalcogenide thin films

Thin films of MoSx were prepared by liquid film deposition of MoS42- solutions in 1,2-diaminoethane (en) and 1,2-diaminopropane (pn) and subsequent thermolysis at temperatures up to 800°C under N2. As the coatings show a high carbon content of up to 30 at.% that influences the morphology and the physical properties, the precursor thermolysis and the solution properties were analysed in detail and correlated to the coating properties. A reduction of the intermediately formed MoS3 by organic residues at approx. 300°C was made out as the main cause of the carbon contamination during the thermolysis of the precursor salts (enH2)MoS4 and (pnH2)MoS4, leading to an immobilisation of the organic carbon. In the corresponding solutions cations of the form [RNH2...H...NH2R]+ could be detected, that result in an incorporation of additional diamine with 3-4 molecules per MoS42- ion in the wet films. This cross-linked structure on the one hand reduces the tendency of the precursor salts to crystallise and thus makes it easier to obtain amorphous precursor films, but on the other hand increases the content of organic residues before thermolysis

Sol-gel electrochromic device

All solid state electrochromic devices have potential applications in architectural and automotive fields to regulate the transmission and reflection of radiant energy. We present the optical and electrochemical characteristics of two solid state windows having the configuration glass/ITO/TiO2-CeO2/TiO2/TiO2-CeO2/ITO/glass and glass/ITO/WOa/TiO2/TiO2-CeO2/ITO/glass where the three internal layers have been prepared by sol gel methods. The preparation of the individual sols and some physical properties of the different sol gel coatings are reported

Wet-chemical processing of transparent and antiglare conducting ITO coating on plastic substrates

The paper reviews a low temperature sol-gel processing of transparent and antiglare conducting Sn doped indium oxide (ITO) coatings. The approach uses already crystalline nanoparticles which can be fully redispersed in an ethanolic sol containing a polymerisable organic binder. Thick single layers up to 600 nm can be deposited by spin and dip coating techniques followed either by a low temperature (<130°C) heat treatment or by a UV light irradiation. Stable resistivity down to 9.