Browsing by Author "Huang, Jung-Chun"

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Helicity-Dependent Terahertz Radiation from Topological Insulator Sb2Te3 Thin Film by Femtosecond Optical Excitation
(2016)
Tu, Chien-Ming
;
Chen, Yi-Cheng
;
Huang, Ping
;
Chuang, Pei-Yu
;
Lin, Ming-Yu
We report on terahertz radiation from topological insulator (TI)Sb2Te3 thin film under ultrafast optical excitation with different helicity. Polarity-reversals of the emitted THz radiation were observed as the helicity of optical pulses reversed. The observed phenomena are coincident with the characteristics of the helicity-dependent photocurrent on TIs. Our work demonstrates the potential applications of surface photocurrents on TIs for opto-spintronics devices.
Substrate-induced structures of bismuth adsorption on graphene: a first principles study
(2016-07-28)
Lin, Shih-Yang
;
Chang, Shen-Lin
;
Chen, Hsin-Hsien
;
Su, Shu-Hsuan
;
Huang, Jung-Chun
The geometric and electronic properties of Bi-adsorbed monolayer graphene, enriched by the strong effect of a substrate, are investigated by first-principles calculations. The six-layered substrate, corrugated buffer layer, and slightly deformed monolayer graphene are all simulated. Adatom arrangements are thoroughly studied by analyzing the ground-state energies, bismuth adsorption energies, and Bi-Bi interaction energies of different adatom heights, inter-adatom distance, adsorption sites, and hexagonal positions. A hexagonal array of Bi atoms is dominated by the interactions between the buffer layer and the monolayer graphene. An increase in temperature can overcome a similar to 50 meV energy barrier and induce triangular and rectangular nanoclusters. The most stable and metastable structures agree with the scanning tunneling microscopy measurements. The density of states exhibits a finite value at the Fermi level, a dip at similar to -0.2 eV, and a peak at similar to-0.6 eV, as observed in the experimental measurements of the tunneling conductance.