Structural, optical and dielectric investigations of electrodeposited p-type Cu₂O

Electrodeposition technique is employed to prepare cuprous oxide (Cu₂O) thin film on fluorine-doped tin oxide (FTO) conducting glass substrate through the reduction of copper lactate in alkaline solution at pH = 12.25. Structural, optical and dielectric properties of the prepared film is investigated by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV–Visible absorbance, photoluminescence (PL) and broadband dielectric spectroscopy (BDS). The structural means (XRD, SEM and EDS) revealed the formation of self-assembled cubic microstructure of Cu₂O with average grain size of around 1.5 μm. The UV–Vis absorbance spectrum gives optical band gap of 2.05 eV. The PL spectrums confirmed the presence of defect centers ascribed to various forms of oxygen (VO1+,VO2+) and copper (VCu1+) vacancies which are responsible for the conduction in the Cu₂O film. The conduction mechanism in the Cu₂O film is successfully described by the correlated barrier hopping (CBH) model in which bipolaron hopping become prominent. The density of defect states N, the effective barrier height W and the hopping distance R_ω are also calculated based on the CBH model. Two dielectric relaxation processes (β₁ and β₂) with Arrhenius temperature dependence and activation energies of 0.31 and 0.48 eV are observed. The fast β₂-relaxation process with activation energy of 0.48 eV is attributed to the Maxwell–Wagner-Sillars (MWS) polarization while the slow β₁-relaxation process with activation energy of 0.31 eV is due to the hopping of the oxygen and copper vacancies.