Annealing-induced changes in optoelectronic properties of sputtered copper oxide films

Copper (I) oxide thin films are deposited on quartz substrates by DC magnetron reactive sputtering. This study examines the effect of post-annealing on their optoelectronic properties in detail. The films are grown by sputtering from copper in an atmosphere of argon and oxygen. The substrate temperature is held at 200 degrees C, while annealing in ambient atmosphere has been carried out between 100 and 600 degrees C. X-ray diffraction analysis, Raman and UV-Vis spectroscopy, and four-probe measurements were used to characterise the films. XRD indicates that deposited Cu2O has a preferred orientation of (110). Post-annealing did not show any measurable conversion to copper (II) oxide until about 500 degrees C, and the process was incomplete even at 600 degrees C. The highest conductivity is observed in the sample post-annealed at 100 degrees C. These results are of substantial technological importance for using Cu2O for a variety of applications, including transparent solar cell fabrication.