Unconventional interplay between heterovalent dopant elements: Switch-and-modulator band-gap engineering in (Y, Co)-Codoped CeO2 nanocrystals.
We report the experimental observation and theoretical explanation of an unconventional interplay between divalent Co and trivalent Y dopants, both of which incur oxygen vacancies in the CeO2 host that has predominantly tetravalent Ce cations. The Co dopant atoms were experimentally found to act as a switch that turns on the dormant effect of Y-modulated band-gap reduction. As revealed by density functional theory (DFT) calculations with structures verified by synchrotron-radiation x-ray measurements, a Co 3d band that hybridizes with Ce 4f band was lowered due to reduced O 2p repulsion arising from oxygen vacancies incurred by Y doping and therefore gave rise to the observed band-gap narrowing effect. Such switch-and-modulator scheme for band-gap engineering in nanocrystal materials can lead to important applications in environmental protection and solar energy harvesting technologies.
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
T S
TS
Wu
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
H D
HD
Li
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
Y W
YW
Chen
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
S F
SF
Chen
Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan.
Y S
YS
Su
National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
C H
CH
Chu
National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
C W
CW
Pao
National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
J F
JF
Lee
Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan.
C H
CH
Lai
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.|Institute of Physics, Academia Sinica, Taipei, Taiwan.
H T
HT
Jeng
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.|National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
S L
SL
Chang
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.|National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
Y L
YL
Soo