Effect of Mg doping on optical and electrical properties of SnO2 thin films: An experiment and first-principles study

Transparent Mg-doped p-type conductive SnO2 thin films were fabricated on quartz substrates by sol-gel method. Effect of Mg doping on structural, morphological, optical, and electrical properties of SnO2 films were investigated. A single phase of tetragonal rutile structure was observed in Mg-doped SnO2 films. The optical bandgap energy of the Mg-doped SnO2 films showed a systematical redshift with respect to the undoped SnO2 film, and the resistivity significantly increased with the increase of Mg concentration. A conduction type transform from n to p was also observed. The strong ultraviolet and comparatively weak blue/green emissions were observed in room temperature photoluminescence, suggesting the dipole-forbidden rule of bulk SnO2 is broken in Mg-doped SnO2 films. These results were supported by first-principles electronic structure calculations.