SnO2 Films Deposited by Ultrasonic Spray Pyrolysis: Influence of Al Incorporation on the Properties

Abstract

Aluminum-doped tin oxide (SnO 2:Al) thin films were produced by an ultrasonic spray pyrolysis method. The effect of aluminum doping on structural, optical, and electrical properties of tin oxide thin films synthesized at 420 ∘C was investigated. Al doping induced a change in the morphology of tin oxide films and yielded films with smaller grain size. SnO 2 thin films undergo a structural reordering and have a texture transition from (301) to (101), and then to (002) preferred cristallographic orientation upon Al doping. The lattice parameters (a and c) decreases with Al doping, following in a first approximation Vegard’s law. The optical transmission does not change in the visible region with an average transmittance value of 72–81%. Conversely, in the near infrared (NIR) region, the plasmon frequency shifts towards the IR region upon increasing Al concentration in the grown films. Nominally undoped SnO 2 have a conductivity of ∼1120 S/cm, which is at least two orders of magnitude larger than what is reported in literature. This higher conductivity is attributed to the Cl- ions in the SnCl 4.5(H 2 O) precursor, which would act as donor dopants. The introduction of Al into the SnO 2 lattice showed a decrease of the electrical conductivity of SnO 2 due to compensating hole generation. These findings will be useful for further studied tackling the tailoring of the properties of highly demanded fluorine doped tin oxide (FTO) films.

Influence of the Curing and Annealing Temperatures on the Properties of Solution Processed Tin Oxide Thin Films

“…As presented in the introduction, the precursor and the method of fabrication have an impact on the electrical properties. Spray pyrolysis has been shown to provide high Hall mobilities (over 10 cm 2 /Vs) with a preferred (211) orientation [32,35]. Our results are similar to the SnO 2 fabricated by the SILAR method [31].…”

“…This could lead to overestimation in the size of the grains, and also, because of the difference in height (R pv ), there could also be a misinterpretation in the assessment of the various grain sizes. As a comparison, only the spray pyrolyzed SnO 2 at 420 • C could lead to a bigger grain size of 142 ± 27 nm, but had a (211) preferred orientation [32]. Therefore, we can understand that the smooth surfaces of the amorphous tin oxide thin films can explain in part the high mobility of the thin films, while the bigger grains can control the higher mobility and conductivity of the polycrystalline tin oxide.…”

Rapid Synthesis of SnO2 Thin Films using Monoethanolamine through Wet Chemical Route

“…The transmittance of the films is decreasing with an increase in wavelength in the nearinfrared (NIR) region of the spectrum. Optical transmission through a rough surface is much affected by the scattering of light having wavelengths near the magnitude of the film surface features (22)(23)(24) . The reflectance spectra of the SnO 2 films in Figure 5(a) shows reflectance below 20% and exhibits a slight increase in reflectance with an increase in wavelength in the NIR region.…”

“…Literature study reveals that the film resistivity was reduced by Fluorine doping from 10 − 2 to 10 − 3 Ωcm (4) . The electrical conductivity of the SnO 2 films can be improved by doping with suitable elements like F, Nb, In, Al and Co (7,12,24,28,31) or by annealing (30,37) .…”

Substrate Temperature Dependence of TiO2 Films Deposited by Spray Ultrasonic Nebulizer Technique

“…It can also be seen that the increased absorption coefficient and substrate temperature occur due to the increased film thickness due to the absorption of light, mostly attributed to the formation stage of anatase and increased grain size. This makes ultrasonic nebulizer deposited thin films excellent candidates for large-scale applications in gas sensors, solar cells, lithium-ion batteries, low emission window, and UV photodetectors [11].…”