Investigating the Influence of Cerium Doping on the Structural, Optical, and Electrical Properties of ZnCexCo2−xO4 Zinc Cobaltite Thin Films

Abstract

Cerium-doped zinc cobaltite spinel thin films, ZnCexCo2−xO4 (0.00≤x≤0.05), were synthesized via spray pyrolysis, and their structural, morphological, optical, and electrical properties were analyzed. X-ray diffraction (XRD) confirmed a cubic spinel structure with a predominant (311) orientation across all compositions. Raman spectroscopy further verified this phase, revealing four active vibrational modes at 180 cm−1, 470 cm−1, 515 cm−1, and 682 cm−1. Scanning electron microscopy (SEM) indicated a uniform grain distribution, while energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of Ce, Zn, Co, and O. Optical measurements revealed two distinct bandgaps, decreasing from 2.32 eV to 2.20 eV for the lower-energy transition and from 3.38 eV to 3.18 eV for the higher-energy transition. Hall effect measurements confirmed p-type conductivity in all films. Electrical analysis showed a reduction in resistivity, from 280.3 Ω·cm to 15.4 Ω·cm, along with an increase in carrier concentration from 1.15 × 1016 cm−3 to 8.15 × 1017 cm−3 with higher Ce content. These results demonstrate that spray pyrolysis is a cost-effective and scalable method for producing Ce-doped ZnCo2O4 thin films with tunable properties, making them suitable for electronic and optoelectronic applications.