Ultrawide bandgap high near ultraviolet transparency amorphous Sn–Al co-doped ZnO thin films

Abstract Transparent amorphous Sn–Al co-doped ZnO thin films (a-SAZO) were prepared by sol-gel spin-coating technique. Sn was inserted with a constant concentration of 2 at.%, and Al was inserted with different concentrations of 1, 2, 3, 4, and 5 at.%. X-ray diffraction patterns indicate that the samples are amorphous. UV-visible spectrometry shows that a-SAZO thin films are a combination of two different amorphous phases; the dominant amorphous phase tends to simulate the amorphous feature and the ultrawide bandgap of the glass substrate, whereas the minor amorphous phase tends to take its proper amorphization and bandgap. The appearance of the dominant amorphous phase is due to the effect of the amorphous glass substrate leading to high near ultraviolet transparency and ultrawide bandgap in the range of 4.00–4.03 eV. The minor amorphous phase shows very low near ultraviolet transparency and bandgap from 3.08 to 3.16 eV. Thus, the control of the amorphous structure of thin films allows attaining the desired near ultraviolet transparency and bandgap. The lowest resistivity was found 6.71 × 10 − 3 Ω cm for Sn 2 at.% - Al 5 at.% concentration. Amorphous tin-aluminum zinc oxide (a-SAZO) with low resistivity can alternate amorphous indium-gallium zinc oxide (a-IGZO).