Enhanced Surface-and-Interface Coupling in Pd-Nanoparticle-coated LaAlO3/SrTiO3 Heterostructures: Strong Gas- and Photo-Induced Conductance Modulation

Abstract

Pd nanoparticle (NP) coated LaAlO3/SrTiO3 (LAO/STO) heterointerface exhibits more notable conductance (G) change while varying the ambient gas (N2, H2/N2, and O2) and illuminating with UV light (wavelength: 365 nm) than a sample without the NPs. Simultaneous Kelvin probe force microscopy and transport measurements reveal close relationships between the surface work function (W) and G of the samples. Quantitative analyses suggest that a surface adsorption/desorption-mediated reaction and redox, resulting in a band-alignment modification and charge-transfer, could explain the gas- and photo-induced conductance modulation at the LAO/STO interface. Such surface-and-interface coupling enhanced by catalytic Pd NPs is a unique feature, quite distinct from conventional semiconductor hetero-junctions, which enables the significant conductance tunability at ultrathin oxide heterointerfaces by external stimuli.

Fractal Nature of Metallic and Insulating Domain Configurations in a VO2 Thin Film Revealed by Kelvin Probe Force Microscopy

“…Various SPM-based techniques have been developed to probe the electrical properties of samples. In particular, Kelvin probe force microscopy (KPFM) is a versatile tool for investigating the local surface potential under ambient conditions 31 33 .…”

Plasmon-Enhanced Surface Photovoltage of ZnO/Ag Nanogratings

“…Kelvin probe force microscopy (KPFM), a variant of atomic force microscopy (AFM), is a technique used to measure the local surface potential of a sample 19 20 21 22 23 . KPFM has the advantage of being a non-destructive ambient-operation tool; it has consequently been successfully used to measure the local doping concentration 20 , the band bending near structural defects 21 , and the domain configuration in a sample containing two distinct phases 22 .…”

“…KPFM also enables us to obtain spatial maps of surface photovoltage (SPV), i.e., changes in the surface potential under illumination. SPV originates from the photo-excitation of carriers and subsequent redistribution of net charges 23 24 . The aforementioned SP-charge coupling should play key roles in the creation and recombination of the charge carriers.…”

“…The polarization of the laser light was adjusted with a linear polarizer to either transverse electric (TE) or transverse magnetic (TM) mode. Prior to the work-function measurements, the samples were annealed at 100 °C for 30 min to remove adsorbed water 22 23 .…”

“…Similar electronic inhomogeneity has also been reported in other KPFM studies of ZnO thin films 19 20 . Doping concentrations and oxygen adsorbates can alter the W S of the ZnO thin films 19 20 23 . Jaramillo and Ramanathan reported that larger (smaller) W S appeared at the grain boundaries (over the grains) of optimally oxidized ZnO thin films 19 .…”