Chemisorptive detection by electrical and nonlinear optical absorption properties of a nanostructured ruthenium-doped zinc oxide film

Ruthenium-doped zinc oxide thin solid films [ZnO:Ru] were deposited on glass substrates using the sol-gel technique by a non-alkoxide route. The gas sensing characteristics of the samples, complemented with structural, optical, and electrical properties were investigated. Raman study confirms the presence of only ZnO wurtzite phase. The observed morphology of the films shows a constant porosity under different deposition conditions, as well as a variation in the crystallite size, ranging from 25 to 35 nm. A modification in the electrical resistance to propane gas as a function of temperature is reported. As a matter of fact, a variation in resistivity up to two orders of magnitude was observed, that makes the films potentially adequate for gas sensors manufacturing. Regarding a remarkable nonlinear optical absorption identified as a dominant physical mechanism of third order optical nonlinearity in the studied samples, we were able to improve the sensitivity for gas sensing by the excitation of a free carrier absorption effect using a non-resonant optical beam.