Jungwoo Oh

The simple synthesis of ultralow‐density (≈2.32 mg cm −3 ) 3D reduced graphene oxide (rGO) aerogels that exhibit high electrical conductivity and excellent compressibility are described herein. Aerogels are synthesized using a combined hydrothermal and thermal annealing method in which hexamethylenetetramine is employed as a reducer, nitrogen source, and graphene dispersion stabilizer. The N‐binding configurations of rGO aerogels increase dramatically, as evidenced by the change in pyridinic‐N/q

To achieve high energy storage on three-dimensional (3D) structures at low cost, materials with high power and long cycle life characteristics have to be developed. We synthesized ZnCo₂ O₄ /reduced graphene oxide (rGO) binary composites in commercial sponges. ZnCo₂ O₄ nanosheets were grown on the surface of GO/sponge through a hydrothermal reaction. The resulting flexible, free-standing ZnCo₂ O₄ /rGO/sponge electrodes were used as

We report a metal-Ge-metal photodetector fabricated on a Ge epitaxial layer grown on Si (100) substrate. Amorphous Ge was used to increase the Schottky barrier height, which resulted in a reduction of the dark current by more than two orders of magnitude. The dark current measured on a photodetector having 1 μm finger width and 2 μm spacing with 25×50 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> active area was 7.5 μA at 3 V. At the wa

N-doped NCO electrodes exhibited excellent electrochemical performance for supercapacitors and hydrogen evolution reaction electrocatalysis in KOH electrolyte.

The authors report on the novel MOSFETs that were fabricated on thin relaxed Ge epitaxial layers grown on Si substrates. With controlled epi-Ge thickness, selectively activated shallow source/drain (S/D) junctions are formed using low dopant activation energy of Ge. The Ge epitaxial layers determine the effective S/D junction depth by selectively activating S/D implantations only in the Ge layers, while suppressing activation in the Si substrates. Low junction leakage current and capacitance are

Mo 2 C is a promising non‐precious hydrogen evolution reaction (HER) electrocatalyst. However, regulating the strong hydrogen adsorption characteristics of Mo 2 C and finding suitable support electrodes are essential processes before Mo 2 C can replace Pt to realize a sustainable hydrogen economy. Herein, the facile synthesis of heterostructured Mo 2 N–Mo 2 C nanoparticles on N‐doped carbonized wood (Mo 2 N–Mo 2 C/N‐CW) as a self‐supported electrode through carbonization and NH 3 plasma treatmen

We report an interdigitated p-i-n photodetector fabricated on a 1-/spl mu/m-thick Ge epitaxial layer grown on a Si substrate using a 10-/spl mu/m-thick graded SiGe buffer layer. A growth rate of 45 /spl Aring//s/spl sim/60 /spl Aring//s was achieved using low-energy plasma enhanced chemical vapor deposition. The Ge epitaxial layer had a threading dislocation density of 10/sup 5/ cm/sup -2/ and a rms surface roughness of 3.28 nm. The 3-dB bandwidth and the external quantum efficiency were measure

We report a high-speed PIN photodetector fabricated on Ge with planar interdigitated p/sup +/ - and n/sup +/ -fingers that were formed by ion implantation into a Ge substrate. The 3-dB bandwidth and the external quantum efficiency were measured on a photodetector having 1-μm finger width and 2-μm spacing with 50 × 50 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> active area. At a wavelength of 1.3 μm, the bandwidth was 1.8, 2.6, and 3 G

Abstract Although increasing attention has been paid to wearable electronic devices in recent years, flexible supercapacitors with high performance remain not readily available because of the limitations of flexible electrode types. A highly conductive 3D macroporous sponge is fabricated by coating poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/silver nanowires (AgNWs) on a commercial sponge using a simple and low‐cost “immersion method.” The fabricated flexible 3D sponge co

We introduce a method for the direct imprinting of GaAs substrates using wet-chemical stamping. The predefined patterns on the stamps etch the GaAs substrates via metal-assisted chemical etching. This is a resist-free method in which the stamp and the GaAs substrate are directly pressed together. Imprinting and etching occur concurrently until the stamp is released from the substrate. The stamp imprinting results in a three-dimensional anisotropic etching profile and does not impair the semicond

To improve overall electrochemical performance, we report and propose zinc cobaltite (ZnCo2O4) nanowire arrays with a simple and precisely controllable NH3 plasma treatment. The NH3 plasma treatment effectively changes the electronic and chemical properties of the pristine ZnCo2O4 by the nitrogen doping and surface functionalization simultaneously. By way of the nanoscale surface/electrical modification of ZnCo2O4, the nitrogen (N)-doped ZnCo2O4 electrodes not only significantly enhanced the ele