Optoelectronic properties of BiCuOSe p-type oxychalcogenides

Abstract

BiCuOSe systems are proposed as candidates to develop transparent p-type semiconductors in the visible region. This work reports the characterization results obtained for the BiCuOSe powders, synthesized by the solid-state reaction (SSR) method through mechanical milling, and nanostructured thin films deposited from the same processed powders using the pulsed laser deposition (PLD) technique. Structural characterization through X-ray diffraction (XRD) showed that the material presents a tetragonal structure with an average crystallite size of 21 nm and a preferential orientation in the (1 0 2) plane. The morphological and particle size evolution of BiCuOSe powders is presented as a function of the milling time. Transmission and scanning electron microscopies confirmed the spherical geometry of the particles in the powders and nanosheets like structure for the films. Particle sizes were also estimated, ranging from 10 to 100 nm for powders and 60 to 70 nm for films. The bandgap values, EG, for BiCuOSe powders were estimated from diffuse reflectance spectra using the Kubelka–Munk method, yielding values close to 0.7 eV. For thin films, EG values were estimated using the Tauc method, obtaining values in the range of 0.8–3.5 eV, depending on the annealing treatment. Additionally, electrical properties were measured in all deposited thin films, confirming the p-type conductivity, a minimal resistivity of 0.0735 Ω cm, hole mobility on the order of 88 cm2/Vs, and carrier concentration of 9.7 × 1018 cm−3.