Elaboration of tin oxide nano-islands through post-deposition thermal treatment

• SnO2 films have been grown onto sapphire by sol–gel dip-coating.
• The thickness of the layers is easily controlled with tin concentration.
• The continuous precursor film splits into isolated islands after a thermal treatment.
• SnO2 nano-islands of 3 nm have been synthesized by decreasing the tin concentration.
• SnO2 nano-islands with such characteristics could be used for optical applications.

Tin dioxide (SnO2) films have been grown onto (006) sapphire substrates by sol–gel dip-coating using tin alkoxide solutions. It is shown, using transmission electron microscopy and atomic force microscopy, that the thickness of the layers is easily controlled with tin concentration. It can vary after the deposition process between few nanometers and few tens of nanometers according to the concentration of the precursor in the sol. A post-deposition thermal treatment forces the continuous precursor film to split into isolated islands. A decrease of the tin concentration in the precursor sol to 100 μM allows the formation of islands of a few nanometers (3 nm) in height and several tens of nanometers in diameter (30 nm). Such height value is very close to the Bohr radius of SnO2.