Grain-size effect on the electrical properties of nanocrystalline indium tin oxide thin films

• Nanometer-sized small grains were observed in the ITO thin films.
• The grain size increased as the post-thermal annealing temperature increased.
• The mobility of ITO thin films increased with increasing grain size.
• The ITO film annealed at 300 °C was an amorphous phase, while the others were polycrystalline structure.

In this paper, we demonstrate the electrical properties, depending on grain size, of nanocrystalline indium tin oxide (ITO) thin films prepared with a solution process. The size distributions of nanometer-sized ITO film grains increased as the post-annealing temperature increased after deposition; the grain sizes were comparable with the calculated electron mean free path. The mobility of ITO thin films increased with increasing grain size; this phenomenon was explained by adopting the charge-trapping model for grain boundary scattering. These findings suggest that it is possible to improve mobility by reducing the number of trapping sites at the grain boundary.