The Properties Of SnO₂ Thin Films By Rare-Earth Dy, Nd, La Doped

Tin (Sn) films were prepared by vacuum thermal evaporation on glass substrates, to obtain the SnO₂ nano-films by heat-treatment in air and oxygen (O₂). Similarly, The nano- SnO₂ films Dy ( Nd , La) doped have been obtained by the same method. Then, the characteristics of films were tested by XRD, FESEM, ultraviolet-visible spectrophotometer, and the influences of the process conditions, doping, heat treatment temperature and time on crystalline structure, crystalline grain dimension, surface topography, electrical, optical and sensitive parameters characteristics of SnO₂ films were analyed in detail.The experimental results showed that the Sn powder as evaporation source to prepare thin films then heat treatment (T=550℃, t=45min, O₂) can obtain the SnO₂ nano-films with good performance (110) plane. The average dimension of the crystal grains was about 47.43nm. When Nd component was 7at%, we can obtain the SnO₂ nano-films with an optimized structure by heat treatment (T=550℃, t=25min, O₂). The average dimension of the crystal grains was about 34.55nm. When Dy component was 9at%: we obtain the SnO₂ nano-films with good performance (101) plane. The average dimension of the crystal grains was about 65.07nm. When La component was 7at%: we can obtain the SnO₂ nano-films with an optimized structure. The average dimension of the crystal grains was about 42.83nm. The SnO₂ films exhibit n-type conductivity and their large resistance. The FE-SEM spectrum showed the surface of films with uniform size particles. There was a few of holes on surface, and the phenomenon of gather of particles was obvious. The dimension of the particles was about 0.3 - 0.8μm.It was shown from the experiment that the Nd (Dy, La) -doping reduces the transmissivity of SnO₂ films by ultraviolet-visible spectrophotometer test (350-900nm).As Nd doping concentration increase, the optical bandgap drops (2.62-3.07ev).When Dy component was 3at%, the results also showed that the SnO₂ films have best sensitivity to acetone. The sensitivity of thin films reaches as 42. When La component was 5at%, the results also showed that the SnO₂ films have best sensitivity to oxygen and ethanol. When Nd component was 5at%, the results also showed that the SnO₂ films have best sensitivity to acetone.