Properties Of Low-emitting Films Based On SnO₂ Prepared Via Sol-Gel Technique

Low-emitting glass with heat insulating property has occurred,since the building energy consumption becomes increasingly serious.Tin oxide,as a typical n-type wide band gap semiconducting material,is extensively applied to many fields due to its outstanding photoelectric properties.For purpose of improving the electrical and optical properties of SnO₂ thin films,a wide variety of dopants such as antimony,fluorine,indium etc.are incorporated.Up to now,numerous synthetic methods have been developed for fabricating thin films,such as spray pyrolysis,chemical vapour deposition,magnetron sputtering and sol-gel.Among these techniques,sol-gel process is considered as a convenient method in comparison to other processes due to its good homogeneity,high efficiency,easily controlled doping levels and mass production capability for uniform large area films.The main objective of this work was to prepare high transmittance in the visible wavelength region incorporated with low transmittance in the infrared spectral region of sol-gel deposited films on glass substrates.All of the chemical reagents used in the experiment were of analytical grade and used as received without further purification.Tin?II?chloride dehydrate?SnCl₂·2H₂O?was dissolved in a solvent mixture of absolute ethanol and n-butanol.The factors of Sb doping content,pulling time and annealing temperature influenced on film properties were studied.The influence of process parameters on hazy and crack appearance was also investigated.All antimony doped SnO₂ thin films are polycrystalline tetragonal rutile phase and no other diffraction lines that correspond to other tin oxide or antimony oxide structures are detected,implying that the Sb doping occurs by substituting Sn atoms in the SnO₂ crystal structure.It is observed that with the pulling time increasing,intensities of the characteristic peaks gradually strengthen.This indicates improvement of the crystallinity of the films with increase in pulling time.The Sb doping content and pulling time have greatly impact on optical and electrical properties of SnO₂: Sb thin film.The transmittance in the IR region remarkably decreases with increasing Sb doping content and pulling time.It is worth noting that the transmittance of 3.0 mol% Sb-doped SnO₂ film in IR region is nearly zero,which is considered to result from the strong IR absorption of free electrons.The hazy and crack appearance of SnO₂: Sb thin film is affected by humidity,temperature of drying,heating rate and cooling rate.