Soo Youn Kim

Homogeneous and stable p-type doping of graphene by MeV electron beam-stimulated hybridization with ZnO thin films

In this work, we demonstrate a unique and facile methodology for the homogenous and stable p-type doping of graphene by hybridization with ZnO thin films fabricated by MeV electron beam irradiation (MEBI) under ambient conditions. The formation of the ZnO/graphene hybrid nanostructure was attributed to MEBI-stimulated dissociation of zinc acetate dihydrate and a subsequent oxidation process. A ZnO thin film with an ultra-flat surface and uniform thickness was formed on graphene. We found that homogeneous and stable p-type doping was achieved by charge transfer from the graphene to the ZnO film.

A Simple 2/3 Modulation Code for Multi-Level Holographic Data Storage

We propose a simple 2/3 modulation code for multi-level holographic data storage (HDS). HDS is a promising method for the optical data storage system. However, two-dimensional (2D) inter-symbol interference (ISI) and inter-page interference (IPI) are weaknesses of HDS systems. Moreover, if multi-level symbols are stored, such systems are more vulnerable to errors. A modulation code can be used to alleviate these problems. Therefore, we introduce a simple 2/3 modulation code for multi-level HDS systems, which is simple and mitigates 2D ISI patterns.

Heat-driven size manipulation of Fe catalytic nanoparticles for precise control of single-walled carbon nanotube diameter

Size-tailored Fe catalytic nanoparticles (NPs) were formed by a heat-driven evaporation process, and precise control of single-walled carbon nanotube (SWCNT) diameter was achieved. The size and surface concentration of Fe NPs significantly decreased with increasing evaporation temperature, which was investigated by transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy. TEM and Raman spectroscopy revealed that the synthesis of SWCNTs with an extremely narrow diameter distribution was achieved and their diameter can be manipulated by evaporation temperature. This diameter-controlled growth of SWCNTs is a step towards SWCNT-based applications.

Optimum Thickness of Al2O3 Support Layer for Growth of Singlewalled Carbon Nanotubes

An optimum thickness of Al2O3 support layer (ASL) for growth of singlewalled carbon nanotubes (SWCNTs) was systematically established. Atomic force microscopy and scanning electron microscopy results clearly revealed that increasing ASL thickness (tASL) resulted in increased ASL grain diameter and root mean square roughness. This significantly affected the diameters of CNTs through the restricted formation of Fe nanoparticles. As a result, SWCNTs and multiwalled CNTs were simultaneously synthesized using ASLs with tASL = 5, 50, and 100 nm, which were confirmed using Raman spectroscopy and transmission electron microscopy. In contrast, ASLs with tASL = 10–30 nm, were suitable for predominant growth of SWCNTs, and ASL with tASL = 15 nm was especially effective for growing high-quality SWCNTs with a small diameter and narrow distribution, 1.1±0.15 nm.

Anchoring Au and Pt Nanoparticles on Multiwalled Carbon Nanotubes via Electron Beam Induced Amorphous Carbon Encapsulation

Au and Pt nanoparticles (NPs) were anchored on multiwalled carbon nanotubes (MWCNTs) via electron beam induced amorphous carbon encapsulation by energy-tunable MeV electron beam irradiation (MEBI) under ambient conditions. MEBI allowed the formation of size-homogeneous Au and Pt NPs on MWCNTs, as observed by transmission electron microscopy. Anchoring of metal NPs was achieved by MEBI-induced amorphous carbon encapsulation. The chemical doping effects of Au and Pt NPs were also verified by Raman spectroscopy. MEBI may provide a facile methodology for anchoring metal NPs to enhance electrical conductivity without destruction of MWCNTs.