The effect of annealing treatment on the structural and optical properties of nanostructured CuxO films obtained by 3D printing

This work studies the effect of post-growth annealing on the structural and optical properties of copper oxide films. Thin films were obtained by 3D printing on glass substrates using ink based on a suspension of CuO nanoparticles. To optimize their structural characteristics and optical quality, the samples were subjected to thermal annealing for 30 min in an argon environment at different temperatures from 250 degrees C to 500 degrees C. The obtained samples were studied by scanning electron microscopy, X-ray diffraction, energy dispersive X-Ray, Raman, optical and photoelectric spectroscopy. Based on the obtained results, the main structural and sub-structural characteristics of the films were established, such as lattice parameters, unit cell volume, texture, sizes of coherent scattering regions, and the level of microdeformation, as well as their dependence on the annealing temperature. In addition, the nature of optical absorption, band gap energies for various types of electronic transitions, and the optical quality of the studied nanostructured copper oxide films were determined. It was shown that CuO films annealed at 350 degrees C have the best crystalline and optical quality. It was established that at an annealing temperature above 400 degrees C, a phase transition from the tenorite phase to the cuprite phase is observed. At the same time, a change in the films' substructural characteristics is already observed at Ta = 400 degrees C. Optimal thermal annealing conditions of CuxO films for effective control of their phase composition have been established.