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Microtube Light-Emitting Diode Arrays with Metal Cores
Tchoe, Youngbin,Lee, Chul-Ho,Park, Jun Beom,Baek, Hyeonjun,Chung, Kunook,Jo, Janghyun,Kim, Miyoung,Yi, Gyu-Chul American Chemical Society 2016 ACS NANO Vol.10 No.3
<P>We report the fabrication and characteristics of vertical microtube light-emitting diode (LED) arrays with a metal core inside the devices. To make the LEDs, gallium nitride (GaN)/indium gallium nitride (InxGa1-xN)/zinc oxide (ZnO) coaxial microtube LED arrays were grown on an n-GaN/c-aluminum oxide (Al2O3) substrate. The micro tube LED arrays were then lifted-off the substrate by wet chemical etching of the sacrificial ZnO microtubes and the silicon dioxide (SiO2) layer. The chemically lifted-off LED layer was then transferred upside-down on other supporting substrates. To create the metal cores, titanium/gold and indium tin oxide were deposited on the inner shells of the microtubes, forming n-type electrodes inside the metal-cored LEDs. The characteristics of the resulting devices were determined by measuring electroluminescence and current voltage characteristic curves. To gain insights into the current spreading characteristics of the devices and understand how to make them more efficient, we modeled them computationally.</P>
Agrawal, Arpana,Tchoe, Youngbin,Kim, Heehun,Park, Joon Young Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.462 No.-
<P><B>Abstract</B></P> <P>The mechanism of surfaces/interfaces and precise control of growth morphology is a key parameter for any specific device application. Herein, we report on a qualitative growth study of molecular beam epitaxy-grown polycrystalline InAs thin films on a lattice-mismatched Si(1 0 0) substrate using atomic force microscopy. The height-height correlation function (HHCF) and power spectral density function (PSDF) were employed to analyze the surface structures. Clear oscillatory behavior in the HHCF for sufficiently larger lateral distances suggests a mound-like morphology, which was confirmed by the existence of a characteristic frequency peak in the PSDF. The growth mechanism is described qualitatively by the Schwoebel barrier (roughening) effect coupled with the Mullins diffusion model (smoothing effect).</P> <P><B>Highlights</B></P> <P> <UL> <LI> HHCF and PSDF were employed to analyze the surface structures. </LI> <LI> Oscillatory behavior in HHCF for larger lateral distances suggests mound-like morphology. </LI> <LI> Existence of characteristic frequency peak in the PSDF further supports mound-like structure. </LI> <LI> Growth mechanism is well explained by the Schwoebel barrier effect coupled with the Mullins diffusion model. </LI> </UL> </P>
Lee, Keundong,Park, Jong-woo,Tchoe, Youngbin,Yoon, Jiyoung,Chung, Kunook,Yoon, Hosang,Lee, Sangik,Yoon, Chansoo,Ho Park, Bae,Yi, Gyu-Chul IOP 2017 Nanotechnology Vol.28 No.20
<P>We report flexible resistive random access memory (ReRAM) arrays fabricated by using NiO<SUB> <I>x</I> </SUB>/GaN microdisk arrays on graphene films. The ReRAM device was created from discrete GaN microdisk arrays grown on graphene films produced by chemical vapor deposition, followed by deposition of NiO<SUB> <I>x</I> </SUB> thin layers and Au metal contacts. The microdisk ReRAM arrays were transferred to flexible plastic substrates by a simple lift-off technique. The electrical and memory characteristics of the ReRAM devices were investigated under bending conditions. Resistive switching characteristics, including cumulative probability, endurance, and retention, were measured. After 1000 bending repetitions, no significant change in the device characteristics was observed. The flexible ReRAM devices, constructed by using only inorganic materials, operated reliably at temperatures as high as 180 °C.</P>