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

Abstract 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 ZnCo 2 O 4 /reduced graphene oxide (rGO) binary composites in commercial sponges. ZnCo 2 O 4 nanosheets were grown on the surface of GO/sponge through a hydrothermal reaction. The resulting flexible, free‐standing ZnCo 2 O 4 /rGO/sponge electrodes were used as the electrodes in a symmetric supercapacitor. ZnCo

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.

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

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

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

Conventional lithography using photons and electrons continues to evolve to scale down three-dimensional nanoscale patterns, but the complexity of technology and equipment is increasing due to diffraction and scattering problems. Physical contact lithography methods, such as nanoimprint and soft lithography, have been developed as an alternative technique. These techniques imprint predefined structures on a stamp to the polymer resist and use the polymer resist as a mask to dry etch the nanostru

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