Luminescent Properties of Nanocomposites Based on Porous Silicon, Nickel, and Nickel Oxide in the Photon Energy Range of 1.4 - 2.9 eV

This paper presents the results of studying the effect of time (5, 6, 7, and 8 minutes) of nickel electrodeposition (Ni ED) at room temperature and annealing at 450°C in an argon atmosphere on the structure, composition, and photoluminescent (PL) properties of mesoporous silicon (meso-PS) and its nanocomposite with Ni (meso-PS/Ni). The SEM and EDX spectroscopy data showed the predominant concentration of Ni on the surface and an insignificant concentration in the near-surface region of the meso-PS. According to Raman and PL spectroscopy data, it was established that after Ni ED in a NiCl2 solution, nickel sub oxide (NiOx) with a band gap of up to 2.8 e V is formed in the meso-PS surface layer, which, after short-term annealing (5 and 6 min), is transformed into nickel monoxide nanocrystals (NiO), which leads to a strong (0.2 - 0.9 eV) “blue” shift of the PL maximum (2.4-2.6 eV) of the nanocomposite with meso-PS/Ni with a multiple increase in the PL amplitude. With an increase in the time of Ni ED and storage in air, NiOx, is not formed, and the detected significant (2–18 times) increase in the PL amplitude with a small “red” shift of 0.05-0.1 eV is presumably associated with the formation of radiative recombination centers in the form of ions Ni in the meso-PS matrix. Annealing in argon in this case leads to a decrease in the PL intensity without shifting the PL maxima.