p-Type copper aluminum oxide thin films for gas-sensing applications

In this study we deposited new, ternary thin films of copper aluminum oxide with p-type and n-type behavior using RF magnetron sputtering for use as chemical gas sensors. p-Type materials are known to be good catalysts and can be combined with the well-known n-type materials for chemiresistive sensors application. Copper aluminum oxide in the delafossite phase CuAlO2 is a ternary oxide that has generated interest as a transparent p-type conducting material, while in the spinel phase CuAl2O4 is known to be n-type. We demonstrated that thin films of copper aluminum oxide with the proper resistance can be successfully applied as p- and n-type resistive gas sensors for ozone detection. We have studied the sputtering deposition conditions from a CuAlO2 sintered target by changing the substrate temperature in inert Ar atmosphere. In addition, post-deposition annealing in O2 atmospheres was also tested. XRD, SEM and Raman investigations were used to characterize the thin films. Selected films with mixed phases of CuAlO2, CuAl2O4 and CuO were tested for gas sensing as resistive chemical sensors, showing promising results with ozone, acetone and ethanol.