Browsing by Author "Chen, Yun-Wen"

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Energy Band Gap Modulation in Nd-Doped BiFeO3/SrRuO3 Heteroepitaxy for Visible Light Photoelectrochemical Activity
(2019-01-09)
Tan, Kok Hong
;
Chen, Yun-Wen
;
Chien Nguyen Van
;
Wang, Hongliang
;
Chen, Jhih-Wei
The ability of band offsets at multiferroic/metal and multiferroic/electrolyte interfaces in controlling charge transfer and thus altering the photoactivity performance has sparked significant attention in solar energy conversion applications. Here, we demonstrate that the band offsets of the two interfaces play the key role in determining charge transport direction in a downward self-polarized BFO film. Electrons tend to move to BFO/electrolyte interface for water reduction. Our experimental and first-principle calculations reveal that the presence of neodymium (Nd) dopants in BFO enhances the photoelectrochemical performance by reduction of the local electron hole pair recombination sites and modulation of the band gap to improve the visible light absorption. This opens a promising route to the heterostructure design by modulating the band gap to promote efficient charge transfer.
Microscopic evidence for the dissociation of water molecules on cleaved GaN(1(1)over bar00)
(2018-01-14)
Wu, Shih-Yu
;
Lang, Liang-Wei
;
Cai, Pei-Yang
;
Chen, Yun-Wen
;
Lai, Yu-Ling
The dissociation of water molecules absorbed on a cleaved non-polar GaN(1(1)over bar00) surface was studied primarily with synchrotron-based photoemission spectra and density-functional-theory calculations. The adsorbed water molecules are spontaneously dissociated into hydrogen atoms and hydroxyl groups at either 300 or 130 K, which implies a negligible activation energy (<11 meV) for the dissociation. The produced H and OH were bound to the surface nitrogen and gallium on GaN(1(1)over bar00) respectively. These results highlight the promising applications of the non-polar GaN(1(1)over bar00) surface in water dissociation and hydrogen generation.