Structural, optical and dielectric investigations of electrodeposited p -type Cu 2 O

Electrodeposition technique is employed to prepare cuprous oxide (Cu 2 O) 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 Cu 2 O with average grain size of around 1.5 μ m. 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 (V_O^1 + , V_O^2 + ) and copper ( V_Cu^ 1 + ) vacancies which are responsible for the conduction in the Cu 2 O film. The conduction mechanism in the Cu 2 O 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 ( β 1 and β 2 ) with Arrhenius temperature dependence and activation energies of 0.31 and 0.48 eV are observed. The fast β 2 -relaxation process with activation energy of 0.48 eV is attributed to the Maxwell–Wagner-Sillars (MWS) polarization while the slow β 1 -relaxation process with activation energy of 0.31 eV is due to the hopping of the oxygen and copper vacancies.