Sungjun Lim

The mechanism of field emission from a metal surface was well explained based on the quantum mechanics in early 20th century. Since then, various materials have been studied for field emitters. However, so far, we have been using only limited materials as a field emitter and an application in some area requires further scientific understandings and technological advancements. In this paper, we review the current status of researches in field emission and emission phenomena of carbon nanotubes (C

A simple approach by direct synthesis of few-layer graphene sheets and transferring them onto flexible substrate is demonstrated. The hydrogen effect on the D band intensity of Raman spectra for few-layer graphene sheets synthesized by chemical vapor deposition (CVD) on Ni-evaporated silicon substrate is investigated by optimizing the mixing ratio of C2H4/H2. While the Ni etchant is used to melt away the squeezed Ni layers between graphene sheet and silicon substrate, the graphene sheet is trans

We have investigated a modification of electronic structures of a carbon nanotube by hydrogen functionalization. Carbon nanotubes were exposed to atomic hydrogen which was generated by a hot tungsten filament in the vacuum chamber. Current-voltage characteristics clearly showed a band gap widening after hydrogenation. This was explained by an enhancement of sp$^3$ hybridization with hydrogen chemisorption on the tube wall. Our density functional calculations also predicted a strong chemisorption

We measured the reflectivities of various single-walled carbon nanotubes (SWCNTs) by using integrated spheres in the spectral range between 0.5 eV and 6.0 eV. The SWCNTs were made using an arc-discharge method with yttrium as a catalyst and were purified using a standard procedure. The SWCNTs were doped either by atomic hydrogen or fluorine gas for unctionalization. We directly fitted the reflectivity spectra to the Drude-Lorentz equation without using Kramers-Kronig transformation. Combining th

Realization of carbon nanotube (CNT)-based transistors requires preexisting semiconducting CNTs, which are not selectively grown by the conventional synthesis approaches. While CNT heterojunction and cross-junction formed with different chiralities have demonstrated the required performance for CNT transistors, these relied on an junction formation accidentally obtained during sample preparation. We propose that hydrogen functionalization of CNTs can transform the electronic structure systematic

Multilayer MoS2 is exfoliated by Li treatment. A thin film of Li-treated MoS2 contains a large portion of 1T phases. This is attributed to the atomic structural change caused by Li insertion, which is investigated using X-ray photoelectron spectroscopy (XPS). In a phase recovery via thermal annealing at 523 K in air, we observe another phase, referred to as the relaxed 1T phase, with a slightly larger binding energy than the 1T phase. After annealing at 523 K in air, the peak intensity of the re

Carbon nanotube (CNT) field emitter was fabricated, and then its emission stability was evaluated with three different anode structures; indium tin oxide (ITO)/glass, ZnS:Cu,Al(green phosphor)/ITO/glass, and Al/ZnS:Cu,Al/ITO/glass. It was found that the electron emission from CNTs to the phosphor layer degrades much faster than the emission to ITO layer does. The current decay time from 100 μA/㎠ to 50 μA/㎠ for ITO/glass and ZnS:Cu,Al/ITO/glass were 250 h and 20 h, respectively. Such rapid decay

In the textile industry, which has low energy efficiency, dyeing and finishing shop accounted for 42 percents of the total energy consumption. In addition, the dyeing and finishing shop has a low standardization level for process and setup, and is based on know-how of operator in the field according to incorrect instruction from the laboratory. To improve the energy efficiency of the dyeing and finishing shop, the process was standardized based on manufacturing data from the dyeing process. This

In order to cope with the rapidly changing market, smal and medium-sized manufacturing companies are planing for introducing colaborative robotsuitable for automated asembly. Thistudy analyzes and evaluates the work of existing proceses and designs and implements aplications that provide quantiative expected efects after introduction of colaborative robots. The aplication is designed on the basis of digital twins, using motion capture sensors to synchronize the actions of workers in the physical

Dyeing and finishing industry is consisted of small- and medium-sized enterprises (SMEs) and has large percentage in energy-related expenditures. The three main research directions for increasing energy efficiency are 1) development of new energy source, 2) improvement of fossil fuel and equipment, and 3) enhancement of process and systematical efficiency. Due to the insufficient capital and resource of SMEs, the last research direction is the most appropriate to apply, which can also lead to ad

Recently, many production lines are becoming more automated and smarter by Industry 4.0 by Germany. However, human workers still make up a large portion of production lines that do not have automated facilities and/or require high skills for complex assembly operations. To analyze workers’ jobs faster and more efficiently, the recent researches have been using a digital human model that digitized worker’s postures and movements using motion capture technology during productions. Digital twin mod

Semiconducting single-walled carbon nanotubes (s-SWCNTs) with lower absorption energy of NO2 gas exhibited higher sensitivity than metallic SWCNTs. The result originated from quantum capacitance of s- SWCNTs, which was readily affected by charge transfer, whereas that of m-SWCNTs showed no change with even more transferred charges. However, m-SWCNT that were aligned polarize adsorbed gases on the surface by a local field that contributed the capacitance changes of m-SWCNT networks. This is a new

We modulated the shape of ZnO nanostructures as nanowires, nanospears, nanowalls, and nanorods by varying the distance between the reactant and the substrate during thermal chemicalvapor deposition. Photoluminescence (PL) data show that the optical quality measured by using the PL intensity ratio of band-edge emission to yellow emission is relatively higher under the synthesis condition of nanowalls. The formation characteristics of the ZnO nanostructures are explained by using an analytical mod