A mechanism of effect of optical excitation on resistive switching in ZrO₂(Y) films with Au nanoparticles

Abstract

A mechanism of effect of optical excitation on resistive switching of dielectric films with embedded metal nanoparticles (MNPs) has been proposed. The mechanism is related to a charging of the MNPs due to internal photoemission of electrons from the MNPs, which results in an increasing of the electric field strength at the MNP surfaces that, in turn, promotes the rupture and restoring of the conductive filaments in the dielectric film. The increasing of the electric filed strength due to the MNP charging as a function of the MNP sizes and positions inside the dielectric films was evaluated using a simple model taking into account the mirror charges on the conductive electrodes of a memristor stack. The single electron charging was found to be essential at small MNP radii (∼1 nm). The proposed mechanism was confirmed experimentally by studying the photoexcitation-induced charging of Au MNPs (with average radius 1.6-1.8 nm) embedded into a 10 nm thick ZrO 2 (Y) film by Kelvin probe force microscopy.

Scanning Kelvin Probe Microscopy investigation of optically induced charge in Au nanoparticles embedded into ZrO-=SUB=-2-=/SUB=-(Y) films

“…2, a−c) were observed, they persisted for a relatively long time (up to a day, and in some cases even longer) after the laser was turned off. It was found earlier in [4] that the appearance of charge spots is associated with the Au NPs charging due to internal photoemission of electrons from Au NPs into ZrO 2 (Y) (Fig. 3).…”

“…2, d). In this case, the charge spots can be associated with the photoionization of deep levels in the ZrO 2 (Y) film and/or in the glass substrate [4]. In the latter case, local accumulation of long-lived photoinduced positive charge is possible only in a thin (thickness about the diffusion length of electrons in glass) subsurface layer of the substrate near its interface with the ITO layer.…”

“…The radiation was focused onto the surface of ZrO 2 (Y):LF-Au film into a spot 1 µm in diameter. The optical properties of the samples studied in this paper were previously studied by optical transmission spectroscopy at 300 K using a Varian Cary 6000i spectrophotometer [4]. It was found that the radiation with λ = 633 nm corresponds to the PR peak in Au NPs, while the short-wavelength radiation with λ = 473 nm is outside the PR band.…”

“…Scanning Kelvin probe microscopy (SKPM) is a powerful method for studying the processes of electric charge local accumulation in such nanocomposite systems [2,3]. In [4] a local charging of a ZrO 2 (Y) film with Au NPs embedded in its thickness was detected upon photoexcitation at a plasmon resonance (PR) wavelength in Au NPs. The observed phenomenon was related to the internal photoemission of electrons from Au NPs in ZrO 2 (Y).…”

Resonant Activation of Resistance Switching in Memristors Based on YSZ Films with Au Nanoparticles

“…Accordingly, the dielectric field strength at the Au NP surface F c increases and decreases synchronously with the HF sinusoidal signal due to the tunnel injection of electrons from the Pt electrode into the Au NP and their extraction back to the Pt electrode. As it has been shown in [21], charging of such a small NP in the same system by even a single electron results in an essential variation of F c (in ~ 10 6 V/cm), which is sufficient to affect the RS. However, at f > f t the electron tunneling cannot follow the external electric field anymore.…”