Abstract:
Cobalt-doped ZnO (CZO) thin films were deposited
on glass substrates at room temperature by radio frequency (RF)
magnetron sputtering of a single target prepared with ZnO and
Co3O4 powders. Changes in the crystallinity, morphology, optical
properties, and chemical composition of the CZO thin films were
investigated at various sputtering powers of 45, 60, and 75 W. All
samples presented a hexagonal wurtzite-type structure with a
preferential c-axis at the (002) plane, along with a distinct change
in the strain values through X-ray diffraction patterns. Scanning
electron and atomic force microscopy revealed uniform and dense
deposition of nanorod CZO samples with a high surface roughness
(RMS). The Hall mobility and carrier concentration increased with
the introduction of Co+ ions into the ZnO matrix, as seen from the
Hall effect study. The gradual increase of the power applied on the target source significantly affected the morphology of the CZO
thin film, which is reflected in the CO2-sensing performance. The best gas response to CO2 was recorded for CZO-60 W with a
response of 1.45 for 500 ppm CO2, and the response/recovery times were 72 and 35 s, respectively. The distinguishing feature of the
CZO sensor is its ability to effectively and rapidly detect the CO2 target gas at room temperature (∼27 °C, RT).
