Junwoo Son

Electrical resistivity and magnetotransport are explored for thin (3–30 nm), epitaxial LaNiO3 films. Films were grown on three different substrates to obtain LaNiO3 films that are coherently strained, with different signs and magnitude of film strain. It is shown that d-band transport is inhibited as the layers progress from compression to tension. The Hall coefficient is “holelike.” Increasing tensile strain causes the film resistivity to increase, causing strong localization to appear below a

The location and nature of fixed charge states in high-k/GaN metal-oxide-semiconductor capacitor structures are characterized by analyzing flatband voltage shifts in high-frequency capacitance-voltage measurements. It is shown that a significant fixed, positive sheet charge forms at Al2O3/GaN interfaces, but not at HfO2/GaN interfaces. Furthermore, an interface dipole is created at HfO2/Al2O3 interfaces, which causes an abrupt shift in the flat band voltage as HfO2 is introduced to form HfO2/Al2

The resistance of superlattices composed of bilayers of ultrathin (∼4 unit cells) of LaNiO3 and ∼3 unit cells of insulating SrTiO3 is explored as a function of temperature and the number of bilayers. All superlattices with more than one bilayer are metallic, whereas a single bilayer is insulating. Two possible interpretations of the electrical characteristics of the superlattices are discussed. The first model involves conduction in parallel-connected layers, whereas the second model assumes cou

Designing energy-efficient artificial synapses with adaptive and programmable electronic signals is essential to effectively mimic synaptic functions for brain-inspired computing systems. Here, we report all-solid-state three-terminal artificial synapses that exploit proton-doped metal–insulator transition in a correlated oxide NdNiO3 (NNO) channel by proton (H+) injection/extraction in response to gate voltage. Gate voltage reversibly controls the H+ concentration in the NNO channel with facile

Abstract The use of gate bias to control electronic phases in VO 2 , an archetypical correlated oxide, offers a powerful method to probe their underlying physics, as well as for the potential to develop novel electronic devices. Up to date, purely electrostatic gating in 3‐terminal devices with correlated channel shows the limited electrostatic gating efficiency due to insufficiently induced carrier density and short electrostatic screening length. Here massive and reversible conductance modulat

In situ exsolution of metal nanoparticles (NPs) is emerging as an alternative technique to deliver thermally stable and evenly dispersed metal NPs, which exhibit excellent adhesion with conducting perovskite oxide supports. Here we provide the first demonstration that Ni metal NPs with high areal density (similar to 175 mu m(-2)) and fine size (similar to 38.65 nm) are exsolved from an Asite-deficient perovskite stannate support (La0.2Ba0.7Sn0.9Ni0.1O3-delta(LBSNO)). The NPs are strongly anchore

Ferroelectric photovoltaics (FPVs) have drawn much attention owing to their high stability, environmental safety, and anomalously high photovoltages, coupled with reversibly switchable photovoltaic responses. However, FPVs suffer from extremely low photocurrents, which is primarily due to their wide band gaps. Here, we present a new class of FPVs by demonstrating switchable ferroelectric photovoltaic effects and narrow band-gap properties using hexagonal ferrite (h-RFeO3) thin films, where R den

Electronic phase modulation based on hydrogen insertion/extraction is kinetically limited by the bulk hydrogen diffusion or surface exchange reaction, so slow hydrogen kinetics has been a fundamental challenge to be solved for realizing faster solid-state electrochemical switching devices. Here we accelerate electronic phase modulation that occurs by hydrogen insertion in VO₂ through vertically aligned 2D defects induced by symmetry mismatch between epitaxial films and substrates. By

A great deal of research has recently been focused on Ruddlesden-Popper (RP) two-dimensional planar faults consisting of intervened [AO] monolayers in an ABO₃ perovskite framework due to the structurally peculiar shear configuration. In this work, we scrutinize the effect of elastic strain on the generation behavior of RP faults, which are electrocatalytically very active sites for the oxygen evolution reaction (OER), in (001) epitaxial LaNiO₃ thin films through by using tw

Programmable optoelectronic devices call for the reversible control of the photocarrier recombination process by in-gap states in oxide semiconductors. However, previous approaches to produce oxygen vacancies as a source of in-gap states in oxide semiconductors have hampered the reversible formation of oxygen vacancies and their related phenomena. Here, a new strategy to manipulate the 2D photoconductivity from perovskite stannates is demonstrated by exploiting spatially selective photochemical

Abstract Reversible phase transformation of correlated oxides by field‐driven ionic process present opportunity to efficiently transduce between ionic transfer and electrical currents in insertion‐based reconfigurable transistors. However, the switching rate of insertion transistors is fundamentally limited by the slow rate of ionic insertion into the lattices of correlated oxides. Here, it is demonstrated that preformed oxygen vacancies in VO 2− δ lattices strongly accelerate proton insertion b

Here, we demonstrate the scalable and continuous production of large coatings with thermochromic VO₂ nanoparticles for “smart” windows.

We report on the voltage-induced insulator-to-metal transition (IMT) of the NbO2 thin films that are deposited under forming gas in the growth chamber. It is shown that the hydrogen in the forming gas gives rise to the abrupt voltage-induced IMT characteristics in NbO2 thin films that are sandwiched between top and bottom Pt electrodes. By a catalytic reaction at the triple boundary between NbO2 and Pt, hydrogen appears to be easily incorporated into the NbO2 lattice and doping significantly low

The control of field-driven ionic redistribution guided by crystal anisotropy increases the retention of H⁺s in VO₂ lattices by locating H⁺ into the deep regions from the interfaces, and thus strengthens long-term memory in artificial synaptic devices.