Joohye Jung

Low-cost label-free electrical detection of artificial DNA nanostructures using solution-processed oxide thin-film transistors.

A high-sensitivity, label-free method for detecting deoxyribonucleic acid (DNA) using solution-processed oxide thin-film transistors (TFTs) was developed. Double-crossover (DX) DNA nanostructures with different concentrations of divalent Cu ion (Cu(2+)) were immobilized on an In-Ga-Zn-O (IGZO) back-channel surface, which changed the electrical performance of the IGZO TFTs. The detection mechanism of the IGZO TFT-based DNA biosensor is attributed to electron trapping and electrostatic interactions caused by negatively charged phosphate groups on the DNA backbone. Furthermore, Cu(2+) in DX DNA nanostructures generates a current path when a gate bias is applied. The direct effect on the electrical response implies that solution-processed IGZO TFTs could be used to realize low-cost and high-sensitivity DNA biosensors.

Improvement in negative bias stress stability of solution-processed amorphous In-Ga-Zn-O thin-film transistors using hydrogen peroxide.

We have investigated the effect of hydrogen peroxide (H2O2) on negative bias stress (NBS) stability of solution-processed amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The instability of solution-processed a-IGZO TFTs under NBS is attributed to intrinsic oxygen vacancy defects (Vo) and organic chemical-induced defects, such as pores, pin holes, and organic residues. In this respect, we added H2O2 into an indium-gallium-zinc oxide solution to reduce the defects without any degradation of electrical performance. The field-effect mobility and sub-threshold slope of the a-IGZO TFTs were improved from 0.37 cm(2) V(-1) s(-1) and 0.86 V/dec to 0.97 cm(2) V(-1) s(-1) and 0.58 V/dec, respectively. Furthermore, the threshold voltage shift under NBS was dramatically decreased from -3.73 to -0.18 V. These results suggest that H2O2 effectively reduces Vo through strong oxidation and minimizes organic chemical-induced defects by eliminating the organic chemicals at lower temperatures compared to a conventional solution process.

Embolisation of indirect carotid-cavernous sinus dural arterio-venous fistulae using the direct superior ophthalmic vein approach

SummaryIndirect carotid-cavernous sinus dural arterio-venous fistulae (cDAVF) can be treated by transarterial and/or transvenous embolisation. This study evaluated patients with cDAVF who underwent transvenous embolisation using the direct superior ophthalmic vein (SOV) approach. Between January 2004 and October 2006, eight cDAVF in seven patients were embolised using direct surgical exposure of the SOV when access to the cDAVF via transarterial or transfemoral venous routes was not feasible. Medical records and imaging studies were retrospectively reviewed. The seven patients consisted of four females and three males from 43 to 65-year-old (mean age, 54.4 years). Six cDAVF lesions were located on the left side and two on the right. All fistulae were successfully embolised and showed clinical improvement. One patient presented after treatment with transient venous congestion on the brain stem, which was relieved by osmotic diuretics and steroids. Direct surgical exposure of the SOV for transvenous embolisation of cDAVF can be effective if the facial vein, inferior petrosal sinus, and internal jugular vein are thrombosed. This approach is easy, safe, and effective when performed by a multidisciplinary team.

Approaches to label-free flexible DNA biosensors using low-temperature solution-processed InZnO thin-film transistors.

Low-temperature solution-processed In-Zn-O (IZO) thin-film transistors (TFTs) exhibiting a favorable microenvironment for electron transfer by adsorbed artificial deoxyribonucleic acid (DNA) have extraordinary potential for emerging flexible biosensor applications. Superb sensing ability to differentiate even 0.5 μL of 50 nM DNA target solution was achieved through using IZO TFTs fabricated at 280 °C. Our IZO TFT had a turn-on voltage (V(on)) of -0.8 V, on/off ratio of 6.94 × 10(5), and on-current (I(on)) value of 2.32 × 10(-6)A in pristine condition. A dry-wet method was applied to immobilize two dimensional double crossover tile based DNA nanostructures on the IZO surface, after which we observed a negative shift of the transfer curve accompanied by a significant increase in the Ion and degradation of the Von and on/off ratio. As the concentration of DNA target solution increased, variances in these parameters became increasingly apparent. The sensing mechanism based on the current evolution was attributed to the oxidation of DNA, in which the guanine nucleobase plays a key role. The sensing behavior obtained from flexible biosensors on a polymeric substrate fabricated under the identical conditions was exactly analogous. These results compare favorably with the conventional field-effect transistor based DNA sensors by demonstrating remarkable sensitivity and feasibility of flexible devices that arose from a different sensing mechanism and a low-temperature process, respectively.

Artificial DNA nanostructure detection using solution-processed In-Ga-Zn-O thin-film transistors

A method for detecting artificial DNA using solution-processed In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) was developed. The IGZO TFT had a field-effect mobility (μFET) of 0.07 cm2/Vs and an on-current (Ion) value of about 2.68 μA. A dry-wet method was employed to immobilize double-crossover (DX) DNA onto the IGZO surface. After DX DNA immobilization, significant decreases in μFET (0.02 cm2/Vs) and Ion (0.247 μA) and a positive shift of threshold voltage were observed. These results were attributed to the negatively charged phosphate groups on the DNA backbone, which generated electrostatic interactions in the TFT device.A method for detecting artificial DNA using solution-processed In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) was developed. The IGZO TFT had a field-effect mobility (μFET) of 0.07 cm2/Vs and an on-current (Ion) value of about 2.68 μA. A dry-wet method was employed to immobilize double-crossover (DX) DNA onto the IGZO surface. After DX DNA immobilization, significant decreases in μFET (0.02 cm2/Vs) and Ion (0.247 μA) and a positive shift of threshold voltage were observed. These results were attributed to the negatively charged phosphate groups on the DNA backbone, which generated electrostatic interactions in the TFT device.

Electrical responses of artificial DNA nanostructures on solution-processed In-Ga-Zn-O thin-film transistors with multistacked active layers.

We propose solution-processed In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) with multistacked active layers for detecting artificial deoxyribonucleic acid (DNA). Enhanced sensing ability and stable electrical performance of TFTs were achieved through use of multistacked active layers. Our IGZO TFT had a turn-on voltage (V(on)) of -0.8 V and a subthreshold swing (SS) value of 0.48 V/decade. A dry-wet method was adopted to immobilize double-crossover DNA on the IGZO surface, after which an anomalous hump effect accompanying a significant decrease in V(on) (-13.6 V) and degradation of SS (1.29 V/decade) was observed. This sensing behavior was attributed to the middle interfaces of the multistacked active layers and the negatively charged phosphate groups on the DNA backbone, which generated a parasitic path in the TFT device. These results compared favorably with those reported for conventional field-effect transistor-based DNA sensors with remarkable sensitivity and stability.

Low-voltage driving solution-processed nickel oxide based unipolar resistive switching memory with Ni nanoparticles

Resistive random access memory (RRAM) combines the advantages of nonvolatile flash memory and volatile dynamic random access memory, avoiding their drawbacks. For the practical use of RRAM, achieving low-voltage driving is strongly desired. Here we report the effect of Ni nanoparticles on solution-processed NiO based RRAM which can realize a one diode one resistor operation by unipolar resistive switching mode and low-voltage driving for future demands. The Ni nanoparticles not only contributed to high oxygen mobility, but also affected effective insulator thickness reduction, and stoichiometric variation in NiO thin films. Furthermore, the Ni nanoparticle embedded device demonstrated good reliability. These findings can enhance the applicability of RRAM as a next generation memory device.

The effect of various solvents on the back channel of solution-processed In?Ga?Zn?O thin-film transistors intended for biosensor applications

This study investigated the effects of exposing solution-processed In–Ga–Zn–O (IGZO) thin-film transistors (TFTs), intended for biosensor applications, to various solvents. Various solvents, such as the nonpolar solvent chlorobenzene and the polar solvents ethanol and deionized (DI) water, were dropped and adsorbed on exposed IGZO channel surfaces. All IGZO TFT devices exhibited a negative threshold voltage shift and a sub-threshold swing degradation, without an accompanying degradation in field-effect mobility. These variations depended on the dielectric constant of the solvents; with the exception of the IGZO TFT device exposed to DI water, they all gradually returned to their initial states.

Hydroxyl radical-assisted decomposition and oxidation in solution-processed indium oxide thin-film transistors

Solution-processed indium oxide TFTs were fabricated by hydroxyl radical-assisted (HRA) decomposition and oxidation. The results show that decomposition and oxidation of carbon is more substantial than metal hydroxides, leading to the elimination of organic residues, correlated to a low interface trap density (S.S. = 0.45 V dec−1, NT = 1.11 × 1012 cm−2) in the device. The resultant HRA indium oxide TFTs exhibit improved electrical characteristics such as the mobility, the on/off current ratio, and the subthreshold swing as well as bias stabilities under PBS and NBS conditions.

Simultaneous engineering of the interface and bulk layer of Al/sol-NiOx/Si structured resistive random access memory devices

In our previous work, the pristine sol-NiOx/Si based device did not exhibit reproducible resistive switching due to the presence of native interlayer oxide. To solve this problem, we investigated high-pressure hydrogen gas annealing at a stack of Al/sol-NiOx/Si to engineer the interface and bulk layer simultaneously. Different from the pure nitrogen high-pressure gas annealing which only affects the bulk properties of the system, we found that the high-pressure hydrogen gas can alter both the interfaces and bulk layers. As a result, the native interlayer oxide thickness at the NiOx/Si interface was reduced and the overall density of oxygen vacancies was increased due to the reduction of atomic hydrogen. Consequently, a good condition for less randomized generation of conducting pathways was secured which led to improved stability of high- and low-resistance states, as well as a larger ratio of high and low resistances regardless of a high free energy of formation at the bottom electrode (Si).