Indium-free large area Nb-doped SnO2 thin film as an alternative transparent conducting electrode

초록

Niobium doped fin oxide (NTO) thin film deposited via facile chemical spray pyrolysis technique on to a large area (10 x 10 cm(2)) glass substrate exhibits better optical and electrical properties. The structural, surface, optical and electrical properties were analyzed by means of XRD, XPS, AFM, SEM-EDS, Hall Effect, and four-point probe techniques. The deposited NTO thin film was found to possess a maximum average transmittance value around 75% due to enhanced optical bandgap (3.77 eV) by Nb-dopant effect. The variation of sheet resistance of the large area (10 x 10 cm(2)) coated thin film over the entire region was studied at every 1 x 1 cm(2) area. The film doped with 1.5 wt% of Nb content showed improved carrier concentration (9.33 x 10(19) cm(-3)), higher free carrier mobility (39.4 cm(2)/V.s), improved electrical resistivity (1.69 x 10(-3) Omega cm) and low sheet resistance (26.5 Omega/square). The temperature dependent electrical measurement was carried out from 200 to 450 degrees C in steps of 50 degrees C to understand the resistance stability of the film. In addition to these studies, we report the surface work function of NTO thin film to identify its suitability in optoelectronic devices. The estimated electrical properties confirm the substitution of Nb5+ in Sn site of SnO2 lattice. Our results indicate the optimized NTO thin film to possess promising optical and electrical transport properties to serve as a better indium-free alternate transparent conducing electrode in various optoelectronic devices.

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