Investigation of the Local Photoconductivity of ZrO2(Y) Films with Embedded Au Nanoparticles by Conductive Atomic Force Microscopy

Abstract

The local transverse photoconductivity of ultrathin (~4 nm) ZrO₂(Y) films with embedded single-layer arrays of Au nanoparticles (~2 nm in diameter) is studied by conductive atomic force microscopy. The ZrO₂(Y) films with Au nanoparticles are formed on glass substrates with transparent conductive indium-tin-oxide sublayers using layer-by-layer magnetron deposition followed by annealing. The peaks observed in the optical absorption spectra of the samples at the wavelength λ ≈ 660 nm are attributed to collective plasmon resonance in dense arrays of Au nanoparticles. The photocurrent between the microscope probe and the indium-tin-oxide sublayer is measured during photoexcitation of the contact between the probe and the sample surface through the transparent substrate by the radiation of a semiconductor laser diode at the plasmon-resonance wavelength. The increase in current through the probe of the atomic force microscope under photoexcitation is attributed to the photon-assisted emission of electrons from the Au nanoparticle into the conduction band of ZrO₂(Y) in a strong electric field applied between the probe and the indium-tin-oxide sublayer under plasmon resonance conditions.