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

Undoped films and films with the addition of NH4F and NH4OH 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 SnO2 nanocrystals. Measurements of surface resistance confirmed the presence of fluorine atoms in the films that were prepared from the solutions with NH4F. Scanning electron microscopy has demonstrated the formation of a dendrite structure and an increase in film porosity with the addition of NH4F and NH4OH to the film-forming solution. Addition of NH4F and NH4OH 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.