(Invited) Non-Aqueous Atomic Layer Deposition of SnO₂ for Gas Sensing Application

Abstract

Tin dioxide thin films are grown at low-moderate temperature using a non-hydrolytic atomic layer deposition process. Granular SnO2 thin films are obtained from tin(IV) tetra-butoxide reacting with acetic acid, at temperatures as low as 75 °C. Influence of pulse length of both reactants and of the deposition temperature on the saturation is studied. A narrow ALD window is established between 150 and 175 °C with a growth per cycle of 0.07 nm and with a linear growth as a function of the number of cycles. Above 200 °C decomposition of the tin precursor is not negligible. Microstructure and morphology of the as-prepared films as well as the influence of the deposition parameters are investigated using electron and atomic force microscopies. The band gap of the obtained films is determined using UV-visible spectroscopy. Finally the use of the SnO2 coated carbon nanotubes as gas sensing layer is discussed.

Atmospheric atomic layer deposition of SnO2 thin films with tin(ii) acetylacetonate and water

“…In both cases, a growth rate of about 1 Å per cyc was observed at relatively low temperatures (<200 °C). At higher deposition temperature, the precursor decomposition cannot be neglected, as stated by Marichy et al 57 Heteroleptic complexes that contain two different ligands, for instance, butyl and acetate as in the case of dibutyltin diacetate (P3), could provide a good compromise between volatility, reactivity, and thermal stability. Several conformers of P3 have been optimized by DFT calculations as demonstrated by Renault et al 58 Among them, three conformers having two terminal oxygen atoms pointing toward the metal atom are the lowest energy ones.…”