Substrate Effect on Liquid Petroleum Gas Sensors of Cuprous Oxide Thin Films Electrodeposited in Acetate Bath

Abstract

Cuprous oxide thin films were electrodeposited in an acetate bath (∼60°C) using FTO, ITO, Ti, and Cu substrates to understand their influence on the surface morphology of the films and their wetting nature against liquid petroleum gas (LPG). According to spectral response and capacitance-voltage analysis, n-Cu2O films resulted in the electrodeposition bath at pH range of 5.7-6.5. In addition, SEM data revealed the substrate effect on crystal morphologies of Cu2O thin films with unique porous and tetrahedron structures of Cu2O having different grain sizes. XRD analysis gives evidence in support of these grain size variations which emphasize that Ti and ITO have the lowest grain sizes of 24 and 30.9 nm, respectively. Following the contact angle measurements and their wetting natures, characterized films were subjected to LP gas sensing evaluations in which, proved that deposited n-Cu2O films on FTO, ITO, and Ti can improve gas sensor performances with their moderate wetting behaviors. Under stable sensing conditions, ITO exhibits the most enhanced LPG response, recovery, and stability over time. In comparison, all the experimental results unveiled that substrates do have a major effect, in optimizing interface properties of Cu2O films to achieve better response in many fields of applications.

Performances of Nano-Structured Cu2O Thin Films Electrochemically Deposited on ITO Substrates in Lactate Bath as Liquid Petroleum Gas Sensors

“…A smaller grain size results in high sensitivity, but a significant reduction in grain size decreases the structural stability of the film due to the small crystallites' deleterious nature on the temporal stability of the sensing platform. 35 The size dependence of gas sensitivity is explained by V. E. Bochenkov and G. B. Sergeev. 3 Recent studies on the gas sensitivity of nanostructured metal oxides [2][3][4] suggest a visible increase when the grain size D < 2 L, where L is the thickness of the surface charge layer.…”

“…After deposition, films were thoroughly cleaned with distilled water and allowed to dry in air at room temperature. 35 Cu 2 O thin film characterization.-The phase of cuprous oxide and the average crystal size were monitored using the X-ray Diffraction (XRD) (Regaku Ultima-IV) operating at 40 kV and 30 mA tube voltage and current with Cu-Kα (λ = 1.5418 Å) as the source of X-rays in the 20°−80°2Ɵ range. The significant effect of the film grain size on the sensitivity and conductance of Cu 2 O films and the inter-planer spacing (d) between the particles can be analyzed by considering the diffraction peaks observed with the XRD analysis by Debye-Scherrer formula and Braggs law given in Eqs.…”

“…A digital microscope (2MP 1000x 8 LED USB Digital Microscope Endoscope) focused on the film contacting surface obtained an average contact angle of three separate distilled water droplets after allowing them to settle on the film surface for ∼10 min. 35 LP gas response measurements.-Gold-plated contact probes placed 1 cm apart on the film surface with optimal contact pressure measure the electrical resistance variation of the Cu 2 O film with and without LPG. Film temperature was maintained constant by mounting the films on a heating platform inside a stainless steel gas perfusion chamber.…”

“…The output electrical resistance of the film was processed using a computer interfaced Dual measurement multimeter (GW INSTEK GDM-9060/9061) at 2 s time intervals. 35 At the beginning of each measurement, the sample chamber was flushed with Nitrogen air, and the substrate was allowed to stabilize at the optimal temperature of 70 °C. At this point, thin film resistance (Ra) was stabilized in its ambient state.…”