• Bulletin of the Korean Chemical Society
• /
• v.35 no.2
• /
• pp.575-580
• /
• 2014

We uniformly coated Eu(III)- and Tb(III)-doped yttrium oxide onto the surface of $SiO_2$ spheres and then characterized them by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction crystallography and UV-Visible absorption. 2D and 3D photoluminescence image map profiles were reported for the core-shell type structure. Red emission peaks of Eu(III) were observed between 580 to 730 nm and assigned to $^5D_0{\rightarrow}^7F_J$ (J = 0 - 4) transitions. The green emission peaks of Tb(III) between 450 and 650 nm were attributed to the $^5D_4{\rightarrow}^7F_J$ (J = 6, 5, 4, 3) transitions. For annealed samples, Eu(III) ions were embedded at a $C_2$ symmetry site in $Y_2O_3$, which was accompanied by an increase in luminescence intensity and redness, while Tb(III) was changed to Tb(IV), which resulted in no green emission.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.172-172
• /
• 2008

By thermal evaporation method, well-aligned ZnO nanowires were synthesized on sapphire substrate at $1000^{\circ}C$ with different oxygen flow rate by using pure ZnO powder (99.999 %). The as-synthesized ZnO nanowires were characterized by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The well-aligned nanowires are single crystalline in nature and perpendicularly grown along the c-axis. Also the growth rate of nanowires, such as diameter and length, had a tendency to increase as oxygen flow rate increased. Based on the PL measurement of ZnO nanowires, we found that the near band edge of emission redshifted with the increasing intensity of the defect-related green emission in proportion to the increase of oxygen flow rate. "This research was supported by the Korea Research Foundation Grant funded by the Korean Government(MOEHRD)" (The Regional Research Universities Program/Chungbuk BIT Research-Oriented University Consortium).

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1444-1445
• /
• 2006

Carbon nanotubes (CNTs) are grown on TiN-Coated silicon substrates at $700^{\circ}C$ using an ICP-CVD method. Ni catalysts for CNT growth are formed using an RF magnetron sputtering system. Post-treatment using hydrogen ions has been performed in the ICP reactor by varying the treatment period. The characterization using various techniques, such as FESEM, HRTEM, and Raman spectroscopy, show that the physical dimension as well as the crystal quality of CNTs are changed by the post-treatment process. It is also seen that the hydrogen ion-bombardment may change the surface structure of CNTs, which may lead to produce better electron emission properties. The physical reason for all the measured data obtained are discussed to establish the relationship between the structural property and the electron emission characteristic of CNTs.

• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.1862-1864
• /
• 2005

Carbon nanotubes [CNTs] are grown on TiN-coated Si substrates at $700^{\circ}C$ by inductively coupled plasma-chemical vapor deposition (ICP-CVD). Pre-treatment of Ni catalysts has been performed using an RF magnetron sputtering system. Structural properties and field-emission characteristics of the CNTs grown are analyzed in terms of the RF power applied and the treatment time used in the pre-treatment process. The characterization using various techniques, such as FE-SEM, AFM, and Raman spectroscopy, show that the physical dimension as well as the crystal quality of CNTs are changed by pre-treatment of Ni catalysts. It is also seen that Ni catalysts with proper grain size and uniform surface roughness may produce much better electron emission. The physical reason for all the measured data obtained are discussed to establish the relationship between the structural property and the electron emission characteristic of CNTs.

• Korean Journal of Optics and Photonics
• /
• v.12 no.2
• /
• pp.115-120
• /
• 2001

In the present study, we described in detail a precise correction method of the copper emission spectra obtained from a highpressure and high-temperature pulsed plasma-jet. The pulsed plasma-jet is initiated from an electro-thermal capillary discharge through a small orifice, and expanded rapidly into an atmosphere. In order to characterize the plasma, fundamental measurements such as the plasma excitation temperature or electron number density are essential. However those spectral lines which are directly related to the excitation temperature or electron number density may be distorted by the spectral response of the optical instruments used. Therefore, in this paper, we discuss some efforts to derive precise correction methods of the copper emission spectra obtained from the pulsed plasma-jet. a-jet.

• Journal of the Semiconductor & Display Technology
• /
• v.21 no.1
• /
• pp.71-74
• /
• 2022

For the process simplification in the fabrication of organic light emitting diode(OLED), top emission OLED (TEOLED) was fabricated without lithium fluoride(LiF) used as an electron injection layer (EIL). After co-deposition of Mg and Ag with a different process conditions, a cathode material adjacent to EIL was optimized when Mg and Ag have a ratio of 1:9 considering sheet resistance and transmittance. From the energy band diagram of TEOLED, band gap difference between Trisaluminium (Alq3) and Mg:Ag cathode show the difference of 0.4 eV according to the usage of LiF The fabricated TEOLED without LiF showed the improvement of 5.2 % and 2.7 % in the luminance and the current density comparing that with LiF. The results show there is no significant difference in OLED characteristics regardless of LIF layer in the TEOLED structures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.37 no.3
• /
• pp.309-313
• /
• 2024

The key to determining the lifetime of OLED device is how much brightness can be maintained. It can be said that there are internal and external causes for the degradation of OLED devices. The most important cause of internal degradation is bonding and degradation in the excited state due to the electrochemical instability of organic materials. The structure of OLED modeled in this paper consists of a cathode layer, electron injection layer (EIL), electron transport layer (ETL), light emission layer, hole transport layer (HTL), hole injection layer (HIL), and anode layer on a glass substrate from top to bottom. It was confirmed that the temperature generated in OLED was distributed around the maximum of 343.15 K centered on the emission layer. It can be seen that the heat distribution generated in the presented OLED structure has an asymmetrically high temperature distribution toward the cathode, which is believed to be because the sizes of the cathode and positive electrode are asymmetric. Therefore, when designing OLED, it is believed that designing the structures of the cathode and anode electrodes as symmetrically as possible can ensure uniform heat distribution, maintain uniform luminance of OLED, and extend the lifetime. The thermal distribution of OLED was analyzed using the finite element method according to Comsol 5.2.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.2
• /
• pp.243-250
• /
• 2012

In this study, we attempted to reduce firing voltage of AC-PDP by alloying MgO protective Layer with CaO. Also, spray coating of single crystal MgO powder has been used to improving Exo-electron emission characteristics and reducing the statistical discharge delay in plasma displays. The properties of discharge depending upon the single crystal MgO powder are investigated. Plasma display having powder coated MgCaO Protective Layer shows lower driving voltage and higher efficacy than of uncoated, conventional panel.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.456-458
• /
• 2004

We proposed a novel triode-type carbon nanotube field emitter arrays in which extracted gate is surrounded by CNT emitters. We carried out 3-dimensional numerical calculations of electrostatic potential for the proposed CNT-FEAs using the finite element method and compared the results with those obtained from the structure of conventional CNT-FEAs. It was found that the proposed structure could reduce the turn-on voltage for electron emission and improve beam focusing.

• Textile Coloration and Finishing
• /
• v.24 no.3
• /
• pp.153-157
• /
• 2012

One of organic dye materials which have been long lasting investigated is rhodamine 6G dye series. This dye has been attracted with considerable interests due to the reason of its promising photochemical properties. In this study, a novel fluorescent dye compound based on rhodamine 6G derivative was synthesized through the reaction of rhodamine 6G hydrazide and indole-3-carboxaldehdyde. Absorption and fluorescent emission spectra of this dye were determined with the properties of solvatofluorochromism. Related electron energy states of the dye compound were also characterized by computational calculations.