Research Topics

Ph. D. Jae-Yeol Hwang

1. Impurity effect in oxide materials

A) Photoluminescence characteristics in rare-earth-material (Pr) modified SrTiO3.
B) Magnetic properties in diluted systems (Co-TiO2, Li,Cr-ZnO, Cu-ZnO)
C) Mechanical and structural study of LiCsSO4.

Oxide materials have various physical properties. In addition to impurity in host oxide materials, the physical properties are drastically changed. I have been studying the additional impurity effect in oxide material to affect on physical properties, such as optical, magnetic, electrical and mechanical properties.

[References]

 

2. Ferroelectricity in perovskite-type materials

A) UV-exposure effect. (PZT)
B) Multi-layer thin film. (PLZT/PZT)
C) Annealing effect of Mn-modified BLT system.
D) Phase transition study of BLT crystals.
E) Fatigue mechanism in perovskites. (BLT)

Ferroelectricity in perovskites was originated from structural variation (distortion). I tried to change microstructure and structural component through artificial external post-process. And then, I studied What the origin of ferroelectric failure is. (understandings the origin of ferroelectricity in perovskites)

[References]

 

3. Studies of MOS & MOSFET-structured thin films and their applications

A) Epitaxial growth of GaN-based MOS structured thin film (BST/GaN, BLT/GaN, Ga2O3/GaN)
B) A study of transparent conduction oxide for GaN-based optoelectronic devices (ZnO:Al)
C) A study of new dielectric layer for MOS-devices

GaN has a lot of potential properties for opto-electronic device applications. To enhance the field effect and device characteristics in GaN-based MOS devices, some new dielectric layer with high-dielectric constant and stable structure required. In the former studies, I found that ferroelectric materials should be good candidate of dielectric layer for GaN-based MOS devices. I made epitaxial ferroelectric layers on GaN substrate and (Tri-layer) transparent epitaxial MOS-stacked capacitor with optical transparency of over 80% in visible spectral region.

[References]

 

4. Current research topics & interest

   - Artificial structured thin-film (nanodots, nanorods, superlattice, and restricted geometries) 
   - Tunable microwave device applications (BST-based)
   - Hybrid-type optoelectronic device applications
   - Epitaxial growth & fabrication of functional materials

 

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Created by Jae-Yeol Hwang  2006. 5. 27