Enhanced ethanol vapour sensing performances of copper oxide nanocrystals with mixed phases

• Formation of the nanoscale CuO/Cu2O heterostructure with mixed phases in CuxOy nano-crystals was done by RTA in 60 s.
• Ethanol vapour sensing studies evidenced that nanoscale CuO/Cu2O nano-crystals are efficient p-type material candidates for sensing.
• Effects of rapid thermal annealing process on sensing gas response of CuxOy nano-crystals have been investigated.
• Faster response and recovery times for ethanol vapour sensors based on 0.9 wt% Zn-doped CuO/Cu2O are reported.
• Mechanisms of ethanol vapour sensing have been proposed in details for CuO/Cu2O heterojunction.

Copper oxide nanostructures are fascinating nanomaterials due to their remarkable electrical, optical, thermal, and sensing properties given that their tunability and the stabilization of specific phases are uniquely possible at the nanoscale dimensions.The present study reports on nano-crystalline copper oxide thin films via a simple synthesis from chemical solutions (SCS) followed by two types of thermal annealing, namely rapid thermal annealing (RTA) and conventional thermal annealing (TA). We report on the enhanced ethanol sensing performances of the device structures based on synthesized copper oxide nanocrystals with one and two distinctly different phases, namely Cu2O, CuO, as well as mixed phases CuO/Cu2O.A gradient in phase change of nano-crystals was observed for annealed samples starting from CuO on the top to Cu2O in their central region. RTA effects on the gas response of the CuxOy nano-crystals have been identified as unprecedented selectivity and sensitivity to ethanol vapours at different temperatures. An increase in resistance value of about one order in magnitude was detected for samples treated by conventional-TA at 400 °C for 30 min at optimal operating temperature of 300 °C and RTA at 525 °C for 60 s at lower optimal operating temperature of 275 °C. It has been observed that the response and recovery times for pure copper oxide-based sensors can be significantly improved by Zn-doping, e.g. from ∼4.1 s and ∼10.5 s to about 3.3 s and 7.2 s, respectively.The obtained results were discussed in details and it provide an exciting alternative for fast, sensitive, and selective detection of trace gases, which could be of several benefits in the technologies dealing with public securities and environmental monitoring applications.

The fabrication of nanoscale CuO/Cu2O heterostructure with mixed phases in CuxOy nano-crystals grown by chemical deposition was done by rapid thermal annealing RTA. Ethanol vapour sensing studies evidenced that nanoscale CuO/Cu2O nano-crystals became an efficient material candidates for sensing after RTA in 60 s. Faster response and recovery times for ethanol vapour sensors based on 0.95 wt% Zn-doped CuO/Cu2O are reported. Mechanisms of ethanol vapour sensing have been proposed in details for CuO/Cu2O heterojunction.Figure optionsDownload as PowerPoint slide