Cuprous Oxide (Cu2O) is a well-known oxide semiconductor which has a great potential to be used in chemical sensing. As a sensor material, in order to improve charge transport characteristics and adsorption capacity of Cu2O thin films, modulating morphology at nano scale is important as it leads to reduced recombination of carriers. The high surface to volume ratio that can be achieved at nano scale also assists charge carrier generation through the associated sensing process. Thus to maximize the sensor performance, careful optimization of surface morphology in terms of both the size and the shape is important. In this study, an enhancement in sensitivity/sensor response to glucose and liquefied petroleum (LP) gas were achieved using nano-cubic n-type Cu2O semiconductor thin film structures that were grown using a surfactant free template assisted electrochemical deposition technique [1]. First, p-type thin nano-cubic Cu2O templates were deposited on Ti substrates in an acetate bath of pH 7.6. These templates upon annealing in air at 200 ºC converted the conductivity to n-type and were used to grow ~ 1 μm thick nano-cubic n-type Cu2O films in an acetate bath of pH 6.0. Cubes were of sizes in the range 150-300 nm. For comparison purposes, microcrystalline n-type Cu2O films of similar thickness were also grown in an acetate bath of pH 6.0.
The study shows that using nano-cubic n-type Cu2O semiconductor thin film structures, the sensitivity/sensor response for glucose and LP gas can be improved significantly which is of great importance from the biomedical and environmental perspectives respectively. The sensitivity for glucose obtained by amperometric measurements using nano-cubic and microcrystalline n-type Cu2O film structures were 2.94 μAμM-1cm-2 and 1.88 μAμM-1cm-2 respectively. These values can be rated as very high compared to most of the sensitivity values reported in literature on non-enzymatic glucoses sensing [2]. At 2 vol.% LP gas in dry air, the LP gas responses obtained by conductimetric measurements showed faster response and recovery times with a two-fold increase in response for n-type nano-cubic Cu2O film sensors (6.5%) compared to n-type microcrystalline film sensors (3.2%), a first such result available in literature according to authors’ knowledge [1].

[1] J. L. K. Jayasingha, K. M. D. C. Jayathilaka, M. S. Gunewardene, D. P Dissanayake and J. K. D. S. Jayanetti, Phys. Status Solidi B, DOI: 10.1002/pssb.201600333

[2] Liqiang Luo, Limei Zhu, Zhenxin Wang, Bioelectrochemistry 88 (2012) 156–163