Soon-jae Kwon

Soft-chemistry Route to P-I-N Heterostructured Quantum Dot Electroluminescence Device: All Solution-processed Polymer-Inorganic Hybrid QD-EL Device

p-i-n heterostructured quantum-dot electroluminescence (QD-EL) device was fabricated by soft-chemical process, which shows a low turn-on voltage comparable to OLEDs. To construct the multilayered device structure, p-type polymer semiconductor was deposited on the ITO glass by sequential process of coating and thermal curing, thereupon a few monolayers of QD was spin-coated. n -type metal-oxide film was deposited on top of the QD luminescence layer by sol-gel method, providing a facile and low-cost route for the ETL fabrication. Prior to solution-processed ETL construction, a post-treatment is performed using cross-linking agent, in order to chemically-immobilize the QDs. As a cathodic electrode, relatively air-stable aluminum was deposited. The constituent material as well as the electronic band structure of the integrated device guarantees operating stability in air and low turn-on voltage.

Structural study of the magnetocaloric material MnFePxAs1−x

We have investigated the structure of the magnetocaloric material MnFePxAs1−x. The broad x-ray diffraction peak at the magnetic phase change indicates that the phase transition is of first order. Local structure information obtained by extended x-ray absorption fine structure shows that the Fe and As atoms might be located in the same layer as the Mn and P atoms. The calculated formation energy per unit cell also gives evidence of the periodic positioning of the As and P atoms.

Electromagnetic PCB pattern modeling techniques for RF hardware simulation of mobile phones

Various different types of PCB pattern modeling methods for new RF co-simulation technique are presented and applied to wireless phone application. PCB electromagnetic (EM) modeling is essential part of new RF combinational simulation - RF components plus PCB 3D pattern concurrently modeled, however, it takes typically few-hours burdensome modeling time. In this paper, several intermediate forms of PCB modeling methods are evaluated in terms of S-parameters and RF specification such as WCDMA adjacent channel leakage ratio (ACLR) and PCB pattern was pick up from actual mobile phone design in 10-layered FR4 PCB stack-up. Compared to full 3D PCB pattern models, divided pattern model shows competitive accuracy within 0.6~2.0 dBm ACLR average difference and seems to be worthy to replace full PCB pattern models. Experimental data shows that divided pattern modeling technique requires only about 12% of practical full 3D PCB modeling time.