Memristive effect in niobium oxide thin films obtained by the pulsed laser deposition

Abstract

NbOx thin films demonstrating the analog resistive switching characteristics in planar geometry were fabricated by the droplet-free pulsed laser deposition from Nb metal targets. The memristive properties of the films were controlled by tuning the oxygen pressure from 0.7 to 8 Pa and the wavelength of the ablative laser (λ = 248 nm or λ = 532 nm). The stoichiometry of the NbOx films was controlled by the X-ray photoelectron spectroscopy, optical and electrical investigations. Variation of the film thickness from 20 to 50 nm affects the resistive switching characteristics. The 20 nm NbO2 films obtained at the oxygen pressure of 1.3 Pa show a volatile memristive switching with a memory window of ON/OFF resistances ∼ 101 after 500 direct current cycles at an operating voltage of 4.5 V. The 30 nm Nb2O5 films fabricated at the oxygen pressure of 4 Pa, showed a gradual increase in device conductivity with successive positive voltage sweeps with an amplitude of +5 V, which is characteristic of non-volatile memristive switching. Thus, the use of NbOx memristive films of different compositions and crystallinity degree will allow creating neuromorphic systems based on the same material by controlling the memristive behavior by the laser synthesis conditions.