The effect of NH4F and NH4OH on the structure and physical properties of thin SnO2 films synthesized by the sol-gel method

Abstract

Undoped films and films with the addition of NH 4 F and NH 4 OH have been prepared by layer precipitation of solutions on glass substrates by sol-gel technology with the use of centrifugation. It has been shown via X-ray diffraction that all films under study are composed of SnO 2 nanocrystals. Measurements of surface resistance confirmed the presence of fluorine atoms in the films that were prepared from the solutions with NH 4 F. Scanning electron microscopy has demonstrated the formation of a dendrite structure and an increase in film porosity with the addition of NH 4 F and NH 4 OH to the film-forming solution. Addition of NH 4 F and NH 4 OH to the solution has resulted in the increase of the gas sensitivity of the films; however, it has been accompanied by a decrease in film transparency and the disappearance of interference peaks in the transmittance spectra.