Preparation of p-type conducting transparent CuCrO2 and CuAl0.5Cr0.5O2 thin films by sol–gel processing

CuCrO2 and CuAl0.5Cr0.5O2 thin films were prepared by sol–gel processing and subsequent two-step annealing in air and inert gas atmosphere. Phase pure films with delafossite structure were obtained by adjusting the respective temperatures. The related phase development strongly affects the optical and electrical performance, giving leeway for optimization. The resulting CuCrO2 (16 Ωcm, transmittance 21%) and CuAl0.5Cr0.5O2 (11 Ωcm, transmittance 49%) films showed p-type conductivity by their positive Seebeck coefficients. The microstructure of the systems was characterized by scanning and transmission electron microscopy and correlated to the growth of different crystalline phases during the annealing steps. Thereby, crystal thermodynamics also affects the respective film performance, alleviating delafossite formation from the amorphous phase.