Jin-Su Oh

Ames Laboratory · The Division of Materials Sciences and Engineering

Reversible conversion over multimillion times in bond types between metavalent and covalent bonds becomes one of the most promising bases for universal memory. As the conversions have been found in metastable states, an extended category of crystal structures from stable states via redistribution of vacancies, research on kinetic behavior of the va...

Niobium superconducting radiofrequency cavities enable applications in modern accelerators and quantum computers. However, the surface resistance significantly deteriorates the cavities’ performance. Nitrogen doping surface treatment can consistently increase cavity performance by reducing surface resistance, but the improvement mechanism is not fu...

Reversible conversion over multi-million-times in bond types between metavalent and covalent bonds becomes one of the most promising bases for universal memory. As the conversions have been found in metastable states, extended category of crystal structures from stable states via redistribution of vacancies, researches on kinetic behavior of the va...

Niobium superconducting radiofrequency cavities enable applications in modern accelerators and quantum computers. However, the surface resistance significantly deteriorates the cavities performance. Nitrogen doping surface treatment can consistently increase cavity performance by reducing surface resistance, but the improvement mechanism is not ful...

Niobium thin films on silicon substrate used in the fabrication of superconducting qubits have been characterized using scanning and transmission electron microscopy, electrical transport, magnetization, quasiparticle spectroscopy, and real-space real-time magneto-optical imaging. We study niobium films to provide an example of a comprehensive anal...

The fundamental challenge underlying superconducting quantum computing is to characterize heterogeneity and disorder in the underlying quantum circuits. These nonuniform distributions often lead to local electric field concentration, charge scattering, dissipation and ultimately decoherence. It is particularly challenging to probe deep sub-waveleng...

Interfacial phase-change memory (iPCM), comprising alternating layers of two chalcogenide-based phase-change materials—Sb2Te3 (ST) and GeTe (GT)—has demonstrated outstanding performance in resistive memories. However, its comprehensive understanding is controversial. Herein, the phase-change characteristic of iPCM is identified using atomic scale i...

The fundamental challenge underlying superconducting quantum computing is to characterize heterogeneity and disorder that lead to local electric field concentration, charge scattering, dissipation and ultimately decoherence. It is particularly challenging to probe deep sub-wavelength electric field distribution under electromagnetic wave coupling a...

Quantum information science harnesses the principles of quantum mechanics to realize computational algorithms with complexities vastly intractable by current computer platforms. Typical applications range from quantum chemistry to optimization problems and also include simulations for high energy physics. The recent maturing of quantum hardware has...

Niobium is commonly used for superconducting quantum systems as readout resonators, capacitors, and interconnects. The coherence time of the superconducting qubits is mainly limited by microwave dissipation attributed to two-level system defects at interfaces, such as the Nb/Si and Nb/air interface. One way to improve the Nb/air interface quality i...

The cross‐sectional transmission electron microscopy (TEM) imaging method is widely used to determine the nanoscale thickness of thin films. However, thin films to be analyzed within TEM samples often have a curved or distorted shape, or poor alignment with the electron beam direction, which can easily overestimate the thickness due to TEM projecti...

In this study, local structural changes induced by electrical SET/RESET operations in single crystalline Ge2Sb2Te5 (GST) nanowires fabricated via the vapor-liquid-solid method have been investigated using nano-scale Extended X-ray Absorption Fine Structure (EXAFS) experiments. Under the aforementioned situation, GST nanowires (NWs) were observed to...

An amorphous TaxMnyOz layer with 1.0 nm thickness was studied as an alternative Cu diffusion barrier for advanced interconnect. The thermal and electrical stabilities of the 1.0-nm-thick TaxMnyOz barrier were evaluated by transmission electron microscopy (TEM) and current density–electric field (J–E) and capacitance–voltage (C–V) measurements after...

Focused ion beam method, which has excellent capabilities such as local deposition and selective etching, is widely used for micro-electromechanical system (MEMS)-based in situ transmission electron microscopy (TEM) sample fabrication. Among the MEMS chips in which one can apply various external stimuli, the electrical MEMS chips require connection...

The quantity of the crystalline phases present in a nanomaterial is an important parameter that governs the correlation between its properties and microstructure. However, quantification of crystallinity in nanoscale‐level applications by conventional methods (Raman spectroscopy and X‐ray diffraction) is difficult because of the spatial limitations...

We report the reaction between thin Ni films and 6H-SiC substrates at relatively low temperatures (<550°C) and the diffusion behavior of carbon during silicide formation. The phase transformation and distribution of chemical constituents were investigated using transmission electron microscopy. About 60 nm of Ni was deposited on 6H-SiC using an e-b...

Memory of texture in hydrogenation–disproportionation–desorption–recombination (HDDR) processed NdFeB magnets was directly observed using electron backscatter diffraction (EBSD). By precise control of dynamic HDDR processing conditions, shape changes of samples were minimized by proper modifications of dimensions of samples subjected to HDDR treatm...

The phase change behavior of a carbon-doped Ge2Sb2Te5 (C-GST) material under direct current (DC) biasing (forward and reverse bias) was investigated via in situ electrical biasing transmission electron microscopy (TEM). Threshold switching was governed primarily by the electrical transition mechanism, as evidenced by the absence of nuclei (during c...

Shot peening of metal surfaces can improve the mechanical properties by inducing plastic deformation and grain refinement at the surface. We examined the samples using state-of-the-art scanning electron microscopy techniques: electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD). These backscattered electron techni...

Understanding the domain switching behavior is important for the design and fabrication of multi-layer ceramic capacitor (MLCC) devices. Although many studies on domain switching using bulk sized BaTiO3 (BTO) have been reported, studies of the actual device are scarce. In this study, the domain switching behavior in BTO was investigated in the actu...