Jin-Koo Chung

Polyaniline and poly(N-vinylcarbazole) blends as anode for blue light-emitting diodes

Polyaniline and poly(N-vinylcarbazole) (PANI:PVK) blends are introduced as an anode, and the advantages are demonstrated for organic light-emitting diodes (LEDs). Compared to the usual PANI network electrodes, use of the blend allows for simpler fabrication and provides a better planarized surface, especially for the device with vapor-deposited emitting layer. PANI is not usually used for blue LEDs because of its strong light absorption in the deep-blue spectral region. This problem is practically solved by the use of the blend.

Step bunching-induced vertical lattice mismatch and crystallographic tilt in vicinal BiFeO3(001) films

Epitaxial (001) BiFeO3 thin films grown on vicinal SrTiO3 substrates are under large anisotropic stress from the substrates. The variations of the crystallographic tilt angle and the c lattice constant, caused by the lattice mismatch, along the film thickness were analyzed quantitatively using the x-ray diffraction technique. By generalizing the Nagai model, we estimated how step bunching resulted in the vertical lattice mismatch between adjacent BiFeO3 layers, which induced the strain relaxation and crystallographic tilt. The step bunching was confirmed by the increased terrace width on the BiFeO3 surface.