Optimizing the resistivity of colloidal SnO2 thin films by ion implantation and annealing

Tin oxide (SnO2) is a critical material for a wide range of applications, such as in perovskite solar cells, gas sensors, as well as for photocatalysis. For these applications the transparency to visible light, high availability, cheap fabrication process and high conductivity of SnO2 benefits its commercial deployment. In this paper, we demonstrate that the resistivity of widely colloidal SnO2 can be reduced by noble gas ion beam modification. After low energy argon implantation with a fluence of 4x10(15) at.cm(-2) at 25keV and annealing at 200 degrees C in air, the resistivity of as-deposited film was reduced from (178+6)mu ohm cm to (133+5)mu ohm cm, a reduction of 25%. Hall effect measurements showed that the primary cause of this is the increase in carrier concentration from (8.1 +0.3)x10(20) cm(-3) to (9.9+0.3)x10(20) cm(-3). Annealing at 200 degrees C resulted in the removal of defect clusters introduced by implantation, while annealing at 300 degrees C resulted in the oxidation of the films, increasing their resistivity. The concentration of oxygen vacancy defects can be controlled by a combination of low energy noble gas ion implantation and annealing, providing promising performance increases for potential applications of SnO2 where a low resistivity is crucial.