ALD modified cross-linked ZnO nanowire sensors for pollutant gases

We focused on the development of multiple nanowires sensors which possess the advantages of single nanowire sensors, but are suitable for industrial application due to their cost-efficiency and scalability of the implemented technology. The proposed approach consists in realizing cross-linked nanowires bridging two electrodes by growing horizontal ZnO NW via hydrothermal growth. The nanowires’ surface was functionalized by deposition of ultrathin layer of inorganic materials using: Atomic Layer Deposition (ALD) cycles for Al
2
O
3
and TiO
2
were used to achieve a high selectivity to target analytes in multi-species environment. The comparison of the sensing properties with the one of bare ZnO device confirmed a strong impact of the ALD surface functionalization.In both cases the net effect is an improvement of the relative response towards both reducing and oxidizing gases tested: one order of magnitude improvement is observed in case of Al based modification for NO
2
, while H
2
S detection has been improved with Ti based ALD modifications. An extensive characterization of the devices was carried out by SEM, TEM, Raman and PL spectroscopy; the correlation with the sensing properties is discussed.