Transport, structural and optical properties of SnO2 transparent semiconductor thin films alloyed with chromium: carrier type conversion

In this work, tin oxide thin films alloyed with chromium up to 50 at.% were prepared via spray pyrolysis method on preheated glass substrates of 480 A degrees C, and the effect of Cr on the structural, optical, electrical and thermo-electrical properties of SnO2:Cr thin films was studied. The results show that all the films grow in polycrystalline form with tetragonal rutile structure. The lattice volume of SnO2:Cr films was found to be minimum at the critical Cr concentration of 15% indicating to two different mechanisms for Cr addition: For low Cr concentration (< 15%) substitutional doping is the involving mechanism, while for more Cr addition, interstitial doping is the dominant one in the studied films. Cr addition in SnO2 films results in reduction of crystallite size, transparency and band-gap, and also varies resistivity and carrier concentration. The remarkable effect of Cr addition was revealed as achieving p-type conductivity in SnO2:Cr films with Cr content ranging 5-15%.