Gas sensing properties of novel CuO nanowire devices

We report on novel gas sensing devices based on cupric oxide (CuO) nanowires which are synthesized on-chip by thermal oxidation of electroplated copper microstructures. This technique enables the direct integration of a multitude of CuO nanowires, which bridge the electrical contacts of a conductometric gas sensor. The CuO nanowire bridges exhibit a huge surface-to-volume ratio and are entirely surrounded by the gas atmosphere, which is a highly favorable gas sensor configuration. As a result, the CuO nanowire gas sensor devices are able to detect carbon monoxide (CO) down to a concentration of 10 ppm and exhibit extraordinary sensitivity to hydrogen sulfide (H2S) where concentrations down to 10 ppb have been detected, even in the presence of humidity. For characterization of the CuO nanowires, X-ray diffraction measurements, transmission electron microscopy and electron energy loss spectroscopy are employed. As no process temperatures higher than 400 °C are required for the fabrication of the CuO nanowire devices, our approach can be employed in a CMOS backend process enabling the realization of a fully silicon integrated CuO nanowire gas sensing device.