Laser synthesis of volatile memristors based on niobium oxide thin films

Abstract

Amorphous NbOx (x ≤ 2.5) thin films with the presence of nanocrystallites, which are promising for use as an active region of volatile memristors were fabricated on c-Al2O3 substrates by the laser synthesis. The films were obtained from targets of niobium metallic during ablation of laser with λ = 248 nm or λ = 532 nm in oxygen pressure range from 5 to 50 mTorr. The effect of the oxygen partial pressure and the wavelength of ablating laser on the chemical, structural, electrical, and optical properties of the films was studied. The optimal conditions for the formation of Nb2O5 and NbO2 stable phases in the films were determined. It was found that the amorphous NbOx phase, which was a source of defects associated with oxygen deficiency, required for the creation of memristors, appeared only at low oxygen pressures in the chamber (∼ 5 ⋅ 10−3 − 10−1 Ohm ⋅ cm) during the film synthesis by the laser with both λ = 248 nm and λ = 532 nm. Volatile memristors of Nb/NbОх/Nb2O5/Pt/с-Аl2O3 (x ≤ 2.5) in cross-bar geometry were created demonstrating long-term stability of operation for 60 DC cycles with ΔRHRS/RHRS < 8% at an operating switching voltage of ∼ 0.5 V.