Dong Han Ha

• Ph. D.
• Korea Research Institute of Standards and Science

We have studied the effects of relative humidity on the conductance of the assembly of poly(dG)–poly(dC) and poly(dA)–poly(dT) DNA molecules. The exponential dependence of conductance on the relative humidity is observed and explained in terms of ionic conduction through the hydration layers around DNA. The poly(dG)–poly(dC) specimen has larger sen...

We have fabricated freestanding nanogears by selectively etching single crystalline Au nanoplates and assembled them tooth to tooth using an atomic force microscope (AFM). The nanogears, with one center hole surrounded by six teeth, are smaller than 500 nm in overall size and 60–70 nm in thickness. We demonstrate that blunt AFM tips on stiff cantil...

Functionalization of carbon nanotubes (CNTs) with polymers such as polyethyleneimine or nafion was found to not change the adsorption properties of gas molecules on CNTs, although functionalization can remarkably enhance the sensitivity of gas sensors. Charge transfer between adsorbed molecules and single-walled carbon nanotubes (SWCNTs) at defect...

We have grown Bi2Sr2Ca1Cu2O8+delta single crystals by the travelling solvent floating zone (TSFZ) method and measured the superconducting properties of various parts of grown crystal boules through Laue photographs, X-ray diffraction, resistivity and magnetization measurement. Generally, a part grown in an early stage shows metallic resistivity beh...

Defects have crucial effects on the electronic and optoelectronic properties of two‐dimensional materials. In this work, we measured the changes in the Raman spectra and electrical conductance of monolayer molybdenum disulfide (MoS2) with increasing defects via thermal annealing in a reducing atmosphere. Raman spectra of the basal plane MoS2 on SiO...

Correction for ‘Raman spectroscopy study of K-birnessite single crystals’ by Dong Han Ha et al. , J. Mater. Chem. A , 2025, 13 , 617–626, https://doi.org/10.1039/D4TA06118G.

Conductive hydrogel bioelectrodes that acquire human physiological information are vital in continuously monitoring various electrophysiological (EP) signals. However, poor adhesion under human physical/chemical activities limits their performance, adversely affecting the...

Raman studies of manganese dioxide (MnO 2 ), a crucial material for sustainable and innovative solutions in energy storage and environmental remediation, have predominantly been conducted on fine-grained aggregates, leaving the identification...

Electricity generation using the piezoelectric effect is an important energy harvesting method. In this study, a solar radiation pressure‐driven crater‐shaped light pressure electric generator (LPEG) device with a Pb(Zr0.52, Ti0.48)O3 (PZT) piezoelectric layer and grained Ag layer is fabricated on GaAs(100) wafer. The electrical output of the devic...

This article reports on the charge transport characteristics across the potential barrier generated by a local dual‐gate modulation at the surface of p‐doped graphene via surface contact on a fluorocarbon (CF) thin film. Owing to simple physical contact, the strong electron affinity of the fluorine atoms in CF stably increases the hole density of g...

Interfaces with surrounding materials, where charged impurities and surface roughness are present, have a significant impact on the electrical and optical properties of 2D materials. In the change of the phonon modes of MoS2 accompanied by thickness variation, the portion caused by intrinsic factors and the portion caused by the interface effect ar...

A light‐pressure electric generator (LPEG) device, which harvests piezoelectric energy using solar radiation enhanced by surface plasmons (SPs), is demonstrated. The design of the device was motivated by the need to drastically increase the power output of existing piezoelectric devices based on SP resonance. The solar radiation pressure can be use...

A piezoelectric energy generating device that produces electricity using plasmon‐enhanced solar radiation pressure (SRP) is developed. The SRP is greatly enhanced on the operational region of the device with a unique crater‐like structure, and direct current is generated successfully on the device. By optimizing the material and thickness of top el...

Implantable strain sensors that reliably detect various biomechanical signals in vivo are essential electronic devices for advanced biomedical and bioengineering technologies. However, it is a challenge to prepare soft implantable...

Van der Waals heterostructures with two-dimensional magnets offer a magnetic junction with an atomically sharp and clean interface. This attribute ensures that the magnetic layers maintain their intrinsic spin-polarized electronic states and spin-flipping scattering processes at a minimum level, a trait that can expand spintronic device functionali...

In this study, we designed an energy harvesting technique, which is beyond the traditional methods of solar energy utilisation (solar cells, etc), based on the radiation pressure used in optical tweezers or solar sails. To increase the intensity of the radiation pressure, we fabricated the GaAs wafer in the form of a volcanic crater structure, whic...

This study was aimed at enhancing surface plasmon resonance through a combination of Ag nanoparticles (NPs) and an asymmetric crater structure capable of concentrating light. The crater structure was fabricated via wet-chemical etching of a GaAs(100) wafer, after which an Ag film was deposited inside, and subjected to rapid thermal annealing to for...

The sensitive characteristics of surface-enhanced Raman scattering (SERS) can be applied to various fields, and this has been of interest to many researchers. Propagating surface plasmon resonance (PSPR) was initially utilized but, recently, it has been studied coupled with localized surface plasmon resonance that occurs in metal nanostructures. In...

We have designed a method of harvesting electrical energy using plasmon-enhanced light pressure. A device was fabricated as a cut cone structure that optimizes light collection so that the weak incident light pressure can be sufficiently enhanced inside the cut cone to generate electrical energy. An increase in the device’s current output is a stro...

Real‐time and continuous monitoring of ultraviolet (UV) radiation in daily activity is critical in diverse fields ranging from personal fitness, cosmetics, to medical aspects. Here, a wearable UV monitoring patch that can be easily fixed/removed at desired locations and provide real‐time and continuous UVA levels in daily life is developed. The wea...

The photoluminescence (PL) and Raman spectra of molybdenum disulfide (MoS2) can be tuned with liquid crystals. A nematic liquid crystal, 5CB, was aligned in a zigzag direction on an MoS2 monolayer flake. The PL and A1g Raman mode peaks of the MoS2 monolayer were shifted by 46 meV and 2 cm-1, respectively, owing to the interaction between MoS2 and t...

Hexagonal (2H) silicon (Si) semiconductors have excellent mechanical properties and optically diverse applications due to their structure and quasi-direct bandgap. The 2H-Si has a relatively lower direct band gap of approximately 1.69 eV at the Γ-point in comparison with that of diamond-silicon (i.e. 3.4 eV), but it is not actually a direct bandgap...

Various intriguing quantum transport measurements for carbon nanotubes (CNTs) based on their unique electronic band structures have been performed adopting a field-effect transistor (FET), where the contact resistance represents the interaction between the one-dimensional and three-dimensional systems. Recently, van der Waals (vdW) gap tunneling sp...

Various postsynthesis processes for transition metal dichalcogenides have been attempted to control the layer number and defect concentration, on which electrical and optical properties strongly depend. In this work, we monitored changes in the photoluminescence (PL) of molybdenum disulfide (MoS2) until laser irradiation generated defects on the sa...

This work reports changes in surface plasmons according to the shape and diameter of nanoholes in thin metal films of varying thickness. Cylindrical and reversed trapezoidal nanoholes were simulated using the finite-difference time-domain (FDTD) method. Nanoholes of 10, 50, and 100 nm diameters were modelled in 40-, 60-, and 80-nm-thick metal films...

We investigated the homogeneity and tolerance to heat of monolayer MoS2 using photoluminescence (PL) spectroscopy. For MoS2 on SiO2, the PL spectra of the basal plane differ from those of the edge, but MoS2 on hexagonal boron nitride (h-BN) was electron-depleted with a homogeneous PL spectra over the entire area. Annealing at 450 °C rendered MoS2 o...

Stretchable gas sensors are important components of wearable electronic devices used for human safety and healthcare applications. However, the current low stretchability and poor stability of the materials limit their use. Here, we report a highly stretchable, stable, and sensitive NO2 gas sensor composed of reduced graphene oxide (RGO) sheets and...

An inorganic-organic hybrid junction has been fabricated by spin coating the p-type poly(3- hexylthiophene-2,5-diyl)(P3HT) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) on an n-type GaN layer. The GaN layer was formed on Al2O3 by metal organic chemical vapor deposition(MOCVD) method. To investigate the effects of P3HT con...

Epidermal electronics are extensively explored as an important platform for future biomedical engineering. Epidermal devices are typically fabricated using high-cost methods employing complex vacuum microfabrication processes, limiting their widespread potential in wearable electronics. Here, a low-cost, solution-based approach using electroconduct...

We report an electric conductance change in a graphene-based device upon molecular adsorption for detecting botulinum neurotoxin (BoNT) using the antibody–antigen binding strategy. This device consists of a 400-µm-wide monolayer of graphene between the source and drain electrodes. As-fabricated devices exhibit p-type behaviors. After modifying grap...

Graphene bubbles often form when graphene and other layered two-dimensional materials are vertically stacked as van der Waals heterostructures. Here, we investigate how graphene bubbles and their related disorders impact the quantum transport behavior of graphene in the absence and presence of external magnetic fields. By combining experimental obs...

As a consequence of their unique electronic band structures, low-dimensional materials such as one-dimensional (1D) single-wall carbon nanotubes (SWCNTs), 2D graphene and various 2D transition-metal dichalcogenides have exhibited intriguing electrical transport properties when incorporated into field-effect transistors. Meanwhile, the van-der-Waals...

The chemical and mechanical stability of hexagonal boron nitride (h-BN) thin films and their compatibility with other free-standing two-dimensional (2D) crystals to form van der Waals heterostructures make the h-BN-2D tunnel junction an intriguing experimental platform not only for the engineering of specific device functionalities but also for the...

We report on crystallographic analyses of one-dimensional GaN nanoneedles grown on a n-GaN epilayer by using hydride vapor phase epitaxy. The nanoneedles were grown with a HCl:NH3 gas flow ratio of 1:38 at 600 °C. The growth time of the GaN nanoneedles affected their morphologies. As time progressed, GaN dots nucleated and then evolved as nanoneedl...

We have investigated temperature-dependent charge transport behavior in thick reduced graphene oxide (RGO) film. Our results show that charges transport through two parallel percolating conducting pathways. One contains large disordered regions as one of its constituents, so its conductance is determined dominantly by variable range hopping (VRH)....

Inelastic electron tunneling spectroscopy is a powerful technique for investigating lattice dynamics of nanoscale systems including graphene and small molecules, but establishing a stable tunnel junction is considered as a major hurdle in expanding the scope of tunneling experiments. Hexagonal boron nitride is a pivotal component in two-dimensional...

We fabricate graphene oxide (GO)-coated fiber bundles via electrostatic deposition of GO sheets on polyester/cotton fiber bundles and investigate the changes in their properties by chemical reduction in a hydroiodic acid solution. The structural properties of GO sheets change rapidly upon exposure to reduction agents but remain under a high defect...

Several studies have focused on synthesizing large-size graphene with an uniform crystal structure. However, graphene synthesized thus far is generally grainy. Grain properties such as size, shape, and crystal orientation are the basis for improving quality. In this study, a nematic liquid crystal is used to observe the several structural propertie...

We demonstrated a nonlithographic method for integrating GaAs nanowire (NW) array-based light-emitting diodes (LEDs) on silicon (Si) substrates. A sub-100 nm hole array on a deposited SiO2 layer was patterned on an entire 2 in. Si wafer based on a sacrificed self-assembled InAs NW array. Then, a core–shell n–p junction GaAs NW array was grown on ex...

We fabricated hybrid structures using combined properties of organic and inorganic materials for application in light emitting diode. The hybrid structures were demonstrated using poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as organic materials a...

We report the hybrid p--n junction based on GaN quantum dots (QDs) as an electron transport layer and poly(3-hexylthiophene-2,5-diyl) (P3HT) as a hole transport layer, which has not been tried for the solar cell until now. The growth of GaN QDs was achieved by the hydride vapor phase epitaxy (HVPE) technique and P3HT film sequentially was coated on...

We studied an inorganic/organic hybrid heterostructure for optoelectronic device and applications. The structure was fabricated using inorganic material consisting of GaN nanoneedles and the hole-conducting polymer PEDOT:PSS. A PEDOT:PSS layer with a thickness of ∼50 nm was deposited using spin coating on GaN nanoneedles grown using an HVPE system....

The electronic properties of graphene depend critically on its lattice orientation and edge type. However, it is very difficult to identify them, and they are accessible only using sophisticated tools. In this paper, we show an easy and reliable way to reveal the lattice orientation and edge type of graphene and graphite flakes, i.e. multi-layered...

We investigated the critical conditions to realize reliable and nano-engineered templates for surface-plasmon enhanced Raman scattering (SERS). Ultra-sensitive SERSs of thymine oligonucleotides were successfully realized on the template of Au nanoparticle arrays which were prepared by the combination of electron-beam lithography and post-chemical m...

Gallium nitride (GaN) nanoflowers were synthesized on a silicon (Si) substrate at growth temperatures of 650 and 600°C and under HCl:NH3 flow ratios of 1:20, 1:30, and 1:40 by hydride vapor phase epitaxy. Numerous nanorod and nanoneedle burs were formed within each nanoflower. The nanoflower size increased with increasing NH3 gas flow rate. The nan...

We have measured the electrical transport along individual λ-DNA molecules stretched across a set of parallel nanoelectrodes using the four-probe method. Up to a relative humidity (RH) of 78%, we find no evidence for electrical transport along λ-DNAs. However, for RHs above 79%, we measure considerable current. The electrical conductance of λ-DNA i...

We report a molecular sensing method based on changes in the electrical conductance of lithographically defined gold nanoparticle (NP) arrays immersed in an analyte solution. As the closely spaced NPs are enlarged due to the analyte-mediated deposition of gold ions onto their surfaces, the conductance increases steeply near the critical time (tc) a...

We grew different morphologies of GaN nanostructures on AlN/Si(111) substrates by using hydride vapor phase epitaxy (HVPE). Among them, we focused on nanoneedles, nanoneedle flowers and nanoneedle chestnuts to determine their different growth mechanisms. The nanoneedle flowers were mainly caused by the roughness of the substrate. However, nanoneedl...

The objective of this study is to evaluate the feasibility of porous silicon (PS) layer as a vapor sensor. We prepared three types of PS layer samples – a single layer, distributed Bragg reflector (DBR) layer, and microcavity layer – and examined their reflectance spectra before, during, and after exposure to different concentrations of various org...

The effect of oxygen partial pressure on stability of high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system has been investigated using x-ray diffraction, resistivity and a.c. susceptibility measurements. It was found that part of the high-Tc phase in Bi-Pb-Sr-Ca-Cu-O system was transformed into the low-Tc phase (80 K) and insulating phases by heating in the te...

To acquire the uniform resist patterns in thermal nanoimprint lithography (TH-NIL), the major considerations include control of the resist, stamp and substrate resist under the imprint condition. Examples of these factors are management of the imprinting pressure, imprinting temperature and releasing temperature. Non-uniform patterns of thermal imp...

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We report the electrical properties of single-walled carbon nanotube bundles aligned between two electrodes with a gap of 8 µm by the alternating current dielectrophoresis method. The resistance increased exponentially as the number of structural defects increased from the oxygen plasma treatment. However, no noticeable change was observed in the c...

We performed surface-plasmon enhanced Raman scattering (SERS) studies of a DNA monolayer on chemically modified Au nanoparticle arrays. Drastic enhancement of Raman signal from DNA molecules was observed on the optimized templates that were prepared by using electron-beam lithography followed by chemical modification. We observed that Raman signal...

GaN nanochestnuts with numerous nanorods and nanoneedles were synthesized on AlN/Si(111) substrate using hydride vapour phase epitaxy (HVPE) method under constant N2 carrier gas flow rate. The formation process of nanochestnuts was systematically investigated and discussed on the basis of the experimental results. The nanochestnuts were analyzed by...

We developed a novel technique for obtaining a residual-strain-free GaN layer by the hydride vapor phase epitaxy (HVPE) method using one-dimensional nanostructures. The GaN layer was grown on a Si(1 1 1) substrate with a conventional AlN film and one-dimensional GaN nanostructures. The nanostructures were grown for 2 h with a HCl:NH3 gas flow ratio...

We grew one-dimensional GaN nanoneedles on AlN/Si(111) substrates at HCl/NH3 gas-flow ratios of 1/20, 1/30, and 1/50 using the hydride vapor-phase epitaxy (HVPE) method. Field emission-scanning electron microscopy (FE-SEM) images of GaN nanoneedles show that the vertical growth rate of GaN nanoneedles increases with increasing gas-flow ratio, but t...

We fabricated one-dimensional GaN nanorods on AlN/Si (1 1 1) substrates at various temperatures, and carrier gas flow amount, using the hydride vapor phase epitaxy (HVPE) method. An AlN buffer layer of 50 nm thickness was deposited by RF sputtering for 25 min. Stalagmite-like GaN nanorods formed at a growth temperature of 650 °C. The diameters and...

We have produced Ni nanocrystals with face centered cubic structure by thermally annealing Ni films deposited on SiO2-covered Si(001) substrates in a flow of mixed hydrogen and argon gas. Ni films thicker than 5 nm self-assemble into highly (111)-oriented Ni nanocrystals on a flat and continuous SiO2 interlayer during the thermal annealing, while N...

We studied the formation of GaN nanorods on AlN-covered Si(111) by the hydride vapor phase epitaxy method. The most well-formed GaN nanorods were obtained at an HCl:NH3 gas flow ratio of 1:40 and a growth temperature of 650°C. A high density of straight nanorods with diameters of about 350nm formed uniformly over the entire substrate. The synthesis...

Periodic Au nanoparticle arrays, fabricated using electron beam lithography, have been modified by chemical reaction in solutions having various concentrations of a reducing agent. As the nanoparticles enlarge due to the formation of additional Au nanolumps on the surface, both the position and intensity of plasmon absorbance of Au nanoparticle arr...

Periodic arrays of pseudotetrahedal-shaped gold nanoparticles were fabricated using nanosphere lithography (NSL) and examined for localized surface plasmon resonance (LSPR). The dependence of the LSPR on particle size of the periodic gold nanostructures was explored for potential application as a new biosensor. With increasing size and height of th...

We have investigated the optimal growth conditions of carbon nanotubes (CNTs) using the chemical vapor deposition and the Ni nanoparticle arrays. The diameter of the CNT is shown to be controlled down to below 20 nm by changing the size of Ni particle. The position and size of Ni particles are controlled continuously by using wafer-scale compatible...

Interdigitated nanogap devices (INDs) were fabricated by the combination of conventional photo/e-beam lithographic techniques and surface-catalyzed chemical deposition (SCD) process. Lithographically-defined gap distances of initial devices were reduced to designed values by simply dipping the devices into the aqueous solution of gold ions and a mi...

The statistical distribution of the Cu site conformations in the CuO2 plane of Bi2Sr2CaCu2O8+y (Bi 2212) has been measured by a fast and local probe Cu K-edge extended x-ray absorption fine structure (EXAFS) as a function of temperature. The Cu site conformations are frozen at T < T* = 120 K ~ 1.4 Tc in two well-defined conformations characterized...

Photoluminescence (PL) properties of a single nanorod containing multiple GaN quantum disks separated by AlGaN potential barriers are investigated using micro-PL spectroscopy. Previous studies reported ensemble spectra from many nanorods. The PL spectra show different features depending on the region of the nanorod excited by the laser, including a...

The hyperpolarizabilities of Au nanoparticles and Au/Ag coreshells were estimated to be ~2times10-41- ~2times10-40 m5/V2 with large electronic polarization processes.

DNA hybridization was electrically detected by monitoring the electric conductance change of a nanodevice comprised of two electrodes separated by a narrow gap whose width was comparable to the size of a nanoparticle. Specific hybridization of a target DNA to the capture DNA on the electrode and the probe DNA on the gold nanoparticle resulted in th...

Integrated nanogap electrodes with separations of several nanometers were fabricated by a simple and highly reproducible method of surface-catalyzed chemical deposition. By this method, multifingered nanogap electrodes of a few nanometers in separation were fabricated with a good yield (over 90%). The fabrication was achieved by immersing the initi...

We have measured the electrical conductance of DNA-linked Au nanoparticle aggregates using the four probe method. FE-SEM images show that the Au nanoparticles are remained intact but not fused together. As the temperature increases under a constant relative humidity, the electrical conductance of Au nanoparticle aggregates linked by 12 base DNA mol...

Movable nanometer-scale structures are fabricated by selective etching of single crystalline Au nanoplates. The nanostructures have arbitrary shapes like gear and alphabet 'A' with in-plane size less than 500 m and thickness of . They could be moved successfully on the substrate using a nanornanipulator installed in a focused ion beam system. Our a...

The cubic nonlinearity of Ag nanoparticles (NPs) with average sizes of ˜ 112 nm and ˜4 nm were investigated using polarization-resolved degenerate four-wave mixing (DFWM) at the regions of non surface plasmon resonance (SPR). The absorption spectra and TEM pictures of Ag NPs with an average size of ˜112 nm indicated wide morphology of size and shap...

We suggest an approach to the fabrication of versatile nanocomponents designed deliberately by selective Ga+ focused-ion-beam etching or Ar+ ion milling of single-crystalline Au nanoplates synthesized by the chemical reaction. The nanocomponents have various shapes like gear, wheel, dumbbell, square and letter “A” with in-plane size of about 400 nm...

Monodispersive size-controlled gold nanoplates were synthesized with high purity from the reduction of hydrogen tetrachloroaurate by reduced amount of sodium citrate, which kinetically controls the reaction pathway, in the presence of poly(vinyl pyrrolidone) (PVP). With the insufficient addition of the reductant, the molar ratio of sodium citrate a...

We have investigated the Ca-doping effects on the structural, electrical and magnetic properties of (Pb0.5Cu0.5)Sr2(Pr1-xCaxCu2Oz(x=0-0.5) bulk ceramic samples. The electrical resistivity, thermoelectric power and magnetic susceptibility measurements reveal that the Ca doping introduces holes into the system and thereby superconductivity with onset...

Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, KoreaReceived January 12, 2004Key Words : Carbon nanotubes (CNTs), Functionalization, EsterificationCarbon nanotubes (CNTs) have been one of the inten-sively-studied topics in the fields of nanoscience andnanotechnology due to their unique electron...

Carbon nanotubes (CNTs) were grown from Co nanoparticles by thermal chemical vapor deposition using C2H2, H2, and Ar gases. The diameters of CNTs were limited by the sizes of the catalytic Co nanoparticles. From 5 nm Co nanoparticles, very long and straight CNTs with diameters below 5 nm were grown. C2H2 was so effective as the carbon feedstock tha...

The magnetic hysteresis loops and the relaxation in Bi2Sr2CaCu2O8 single crystals of various doses of columnar defects (CDs) are studied mainly focusing on physical nature of anomalous second magnetization peak (SMP). With increasing CD density up to a matching field of 100 G, it is observed that the magnetization around the second peak systematica...

We report direct measurements of electrical transport through poly(dA)-poly(dT) and poly(dG)-poly(dC) DNA molecules containing identical base pairs. The observed experimental results suggest that electrical transport through DNA molecules occurs by polaron hopping. We have also investigated the effect of gate voltage on the current-voltage curve. I...

We have observed the effects of cation substitution on the oxygen loss behavior of YBa2-xSrxCu3Oy and Y1-zCazBa2Cu3Oy superconductors. Thermogravimetric analysis shows that, due to the local structural distortion, the Sr substitution establishes a new oxygen state with a larger activation energy on the Cu-O chain. Ca substitution at the Y site loca...

We synthesized the electron-doped infinite-layer superconductor Sr0.9La0.1CuO2 in the high-pressure condition of about 4 GPa. Structural and low-field magnetization studies demonstrated that the superconducting properties of our samples were far superior to any reported results.

We report the high-pressure synthesis of the electron-doped infinite-layer superconductor Sr0.9La0.1CuO2. A Rietveld analysis using X-ray powder diffraction data showed that, within the resolution of the measurement, the sample was purely an infinite-layer structure without any discernible impurities. The superconducting volume fraction and the tra...

We have observed the effects of cation substitution on the charge distribution and superconductivity of Y1−xCaxBa2Cu3Oy and YBa2−zLazCu3Oy. As Ca concentration increases, hole concentration on the CuO2 plane increases beyond the optimum region due to the hole transfer from the Cu–O chain to the CuO2 plane. However, it decreases as the holes move fr...

The magnetization of iodine intercalated Bi2Sr2CaCu2O8(I + Bi-2212) single crystal has been measured as a function of magnetic field H and temperature T. The extracted fluctuation part of the magnetization exhibits a critical behavior consistent with the three dimensional XY model. The static critical exponent ν is 0.99 ± 0.1, which is increased fr...

We have studied the Ar annealing effect on Tc of Y0.85Ca0.15Ba2−xCu3Oy (x = 0.0, 0.5 and 1.0) samples, Ar annealing was carried out at 480°C for 15 min ∼ 10 h. As the annealing time increases, Tc of the x = 0.0 and 0.5 samples first gradually increases to a maximum value, then it decreases slowly suggesting the assintered samples are in the over-do...

We have measured the electrical properties of YB2Cu3Oy/SrTiO3/YB2Cu3Oy (YBCO/STO/YBCO) multilayers prepared by the pulsed laser deposition method under the various deposition conditions of insulating STO layer. Superconducting properties of both YBCO layers are sensitively affected by the deposition temperature, Ts, of insulating STO layer. Tc of l...

For the flux pinning enhancement of (Sm0.5Y0.5)Ba2Cu3O7−δ superconductors we have developed a fabrication method of zone-melting-growth with CeO2 addition to the calcined (Sm0.5Y0.5)Ba2Cu3O7−δ powder. To analyze the effect of CeO2 addition, a zone-melted sample without CeO2 addition was fabricated using the same process. Microstructure analysis of...

We have measured the weight change of YBa2−xSrxCu3Oy () ≤ x ≤ 1.0) samples with heating each up to 950°C at a rate of 2°C/min. in Ar. For pure Yba2−xSrxCu3Oy, there is a maximum around 480°C in the curve of temperature derivative of weight, whereas, another maximum was observed around 630°C for Sr-substituted ones. Assintered samples show sharp sup...

We compared c-axis tunneling characteristics of small stacked intrinsic Josephson junctions prepared on the surface of pristine, I-, and HgI2-intercalated Bi2Sr2CaCu2Oy (Bi2212) single crystals. Relation between the interlayer coupling and the in-plane gap, estimated from I–V characteristics, seems to contradict to the interlayer pair tunneling mec...

We have corrected the impurity effect on the characterization of Y1−xCaxBa2Cu3Oy superconductors prepared by the solid state reaction method. Although the samples have sharp superconducting transition, tiny peaks of BaCuO2 phase are included in the X-ray diffraction (XRD) patterns suggesting a part of Ca ions entered onto the Ba-site. Rietveld anal...

We have measured the weight change of YBa2-xSrxCu3Oy (0 ≤ × ≤ 1.0) samples with heating each up to 950°C at a rate of 2°C/min. in Ar. For pure YBa2Cu3Oy, there is a maximum around 480°C in the curve of temperature derivative of weight, whereas, another maximum was observed around 630°C for Sr-substituted ones. As-sintered samples show sharp superco...

We have studied the Ar annealing effect on Tc of Y0.85Ca0.15Ba2-xSrxCu 3Oy (x = 0.0, 0.5 and 1.0) samples. Ar annealing was carried out at 480°C for 15 min ∼ 10 h. As the annealing time increases, Tc of the x = 0.0 and 0.5 samples first gradually increases to a maximum value, then it decreases slowly suggesting the assintered samples are in the ove...

The magnetization and resistivity of Bi₂Sr₂CaCu₂O₈ (Bi-2212) single crystals have been measured as a function of magnetic field H and temperature T. The extracted fluctuation part of the magnetization and conductivity exhibit critical behavior consistent with the three dimensional XY model. The dynamic cr...