Influence of substrate temperature on the electrical performance of SnO2:Sb / SnO2:Er homostructure

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Abstract
08-089 Luis Vicente de Andrade Scalvi Santos, S.B.(Universidade Estadual Paulista); Boratto, M.H.(Universidade Estadual Paulista); Scalvi, L.V.(Universidade Estadual Paulista); Tin dioxide (SnO2) has growing interest due to numerous applications, as in optoelectronic devices and gas sensors. It is a wide bandgap (3.6 - 4.0 eV) oxide semiconductor, naturally n-type due to oxygen vacancies and interstitial Sn atoms acting as donors in the matrix. SnO2 thin films doped with 1% of Er3+ and 4% of Sb5+ were deposited by sol-gel dip-coating, forming a homostructure. During deposition the substrate temperature was varied between room temperature and 90°C (average value due to heat loss during immersion). Er3+ acts as acceptor in the matrix, leading to high charge compensation. On the other hand, Sb5+ acts as donor, improving the n-type conduction. Then, the coupling of these materials in the homostructure leads to a step in the conduction and valence bands, due to Fermi level equality. Cyclic voltammetry results showed a capacitive behavior, with average hysteresis of 0.45. For films grown with higher substrate temperature (90°C) a memristor behavior was observed when scanned below 1 V/s along with 2 to 4 times increase in electrical conduction when compared to homostructures grown at room temperature. The Bode plots show that these samples have impedance of 102 and 106 ohms for frequency of 106 and 102 Hz respectively. The graphs also show a phase difference ranging from -20 to -90 degrees for homostructures deposited at higher temperature, leading to behavior ranging from resistive to capacitive (typical of a memristor). The homostructures presents transmittance above 80% and fair surface homogeneity. Higher temperatures increase the near infrared transmittance (800 - 1800nm), which can be related with a lower free electron concentration. Conductivity also increases for films grown at higher temperature substrate and may be associated with the increase of the crystallites or even decreasing the amount of Sb atoms at the grain boundary, thus reducing electron scattering. This work is supported by CNPq, CAPES and FAPESP (process 2016/16423-6).
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