Jongwook Lee

Hydrogen passivation of visible p‐i‐n type thin‐film light‐emitting diodes

The effects of hydrogen passivation on the performance of visible p‐i‐n thin‐film light‐emitting diodes (TFLEDs) have been investigated. The TFLEDs were fabricated using a photochemical vapor deposition method. The hydrogenation process was performed using an inductively coupled plasma system at a rf power of 800 W and a process pressure of 20 mTorr for 30 min. It was found that hydrogenation dramatically improved the performance of these TFLEDs. The threshold voltage was decreased by about 1 V, the electroluminescence (EL) peak shifted from 704.5 to 689 nm, the EL intensity increased by a factor of 3, and the brightness increased from 1 to 24 cd/m2 by 24 times.

Dramatic improvement of performance of visible hydrogenated amorphous silicon carbide based p‐i‐n thin‐film light‐emitting diodes by two‐step hydrogenation

The effects of two‐step hydrogenation on the performance of visible p‐i‐n thin‐film light‐emitting diode (TFLED) have been investigated. The TFLEDs were fabricated by a photochemical vapor deposition (CVD) method. A hydrogenation process was performed in two steps: One was an in situ hydrogenation process using a photo‐CVD system and the other an ex situ hydrogenation process using a plasma apparatus after TFLED fabrication. It was found that the performance of visible a‐SiC:H‐based p‐i‐n TFLEDs was drastically improved by a two‐step hydrogenation process. The threshold voltage decreased by about 3 V, the electroluminescence peak shifted towards a shorter wavelength, from 680 to 590 nm, and the brightness increased from 1.3 to 128 cd/m2.

Ex situ hydrogen passivation effect of visible p-i-n type thin-film light-emitting diode characteristics

The effect of ex situ hydrogen passivation process on the performance of visible hydrogenated amorphous silicon carbide (a-SiC:H)-based p-i-n type thin-film light-emitting diodes has been investigated. An ex situ hydrogen passivation process dramatically improved the device performance; that is, the threshold voltage decreased by about 5 V, the electroluminescence (EL) intensity increased by a factor of about 3, and the EL peak shifted toward a short wavelength from 700 to 600 nm, resulting in an increase of the brightness from 1 cd/m2 to 35 cd/m2. This improvement of device performance is caused by the passivation of interface states in the p/i and i/n interfaces as well as midgap states in the luminescent active intrinsic a-SiC:H layer by hydrogen atoms. A process time dependence of the ex situ hydrogen passivation effect on the device performance also has been studied.

In situ hydrogenation of visible a-SiC:H-based p - i - n type thin-film light-emitting diodes using the photochemical vapour deposition method

The effects of in situ hydrogenation on the performance of visible a-SiC:H-based p - i - n type thin-film light-emitting diodes (TFLEDs) have been investigated. The TFLEDs were fabricated with a photochemical vapour deposition method. In the process of TFLED fabrication, with a stream of of 50 sccm and ultraviolet light irradiation at a substrate temperature of and a process pressure of 0.3 Torr for 30 min, in situ hydrogenation was performed at the base of a p layer with various thicknesses of i-a-SiC:H layers (0, 10, 20 and 30 nm). It was found that the performance of visible TFLEDs was dramatically improved by in situ hydrogenation. With in situ hydrogenation after deposition of the 30 nm thick luminescently active i-a-SiC:H layer, the threshold voltage was decreased by about 2 V, the electroluminescence peak shifted from 680 nm to 625 nm and the brightness increased from to .

Study on the synchronous e-learning platforms for dissemination of traditional dance

The aim of this research is to propose the synchronous e-learning platforms and courses for the dissemination of traditional dance as an intangible cultural heritage in danger. The research process consisted of (1) case study on e-learning platforms of intangible cultural heritage and synchronous e-learning platforms, (2) composing the education content, (3) experiment, (4) analysis of results, (5) discussion, and (6) conclusion.

Hydrogenation Time Dependence of a-SiC:H-Based P-I-N Thin Film Visible Light-Emitting Diode Characteristics

The hydrogenation time dependence of hydrogenation effects on the performance of a-SiC:H-based p-i-n thin film light-emitting diodes (TFLEDs) in the visible range has been investigated. It was found that hydrogenation markedly improved the device performance, and that increasing the hydrogenation time beyond a saturation point degraded the device performance; that is, as compared with the performance of a TFLED hydrogenated for a short time (~15 min), the threshold voltage increased slightly, the EL peak shifted towards a longer wavelength, and the brightness decreased. In particular, after hydrogenation for 45 min, the brightness decreased to 15 cd/m2.

Hydrogen passivation effects on performance of visible thin-film light-emitting diodes (TFLEDs)

The effects of hydrogen passivation on the performance of visible thin-film light-emitting diodes (TFLEDs) have been investigated. The TFLED with hydrogen passivation exhibits lower threshold voltage (by about 3 V), higher brightness (about 33 times), and much shorter electroluminescence (EL) peak wavelength (from 704.5 nm to 600 nm) and higher EL intensity than that without hydrogen passivation.

A study on the e-learning for Korean traditional dance

In this paper, we propose a digital learning environment for the education of components of Korea traditional dance. This study analyzes the existing apprenticeship contents and training methods. And we propose a digital teaching methods that can increase the learning effect. The educational content of Seungmu(monks dance) is consist of stepping, keeping time, motion, emotion and rhythmic pattern. Training method are direct instruction, direct demonstration and explaining metaphor. We propose learning methods to increase the learning effect and technology to reflect the intention of each elements. We made the prototype for education of stepping in Seungmu elements.

Experiment on the e-learning of traditional dances through the utilization of stereoscopic

The aim of this paper is to propose e-learning platform through utilization of stereoscopic video conferencing for the education of traditional dance. Two Experiments were conducted on educators and students. To the educator, the stereoscopic video conferencing diminishes the online social distance and brings a sense of reality. To the students, the stereoscopic video conferencing creates more educational motivation than regular video conferencing platforms.

An approach to the reduction of time delay in a networked performance

Reduction of time delay is a critical issue for better interaction in a networked performance. By transmitting an avatar created by skeleton data from Kinect, time delay can be reduced compared to video transmission due to small data. Even though this approach is weak in the realistic aspect, the avatar can be manipulated in simple and various ways, so that it has many advantages and better interactivity.