Browsing by Author "Su, Shu-Hsuan"

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Anti-site defect effect on the electronic structure of a Bi2Te3 topological insulator
(2018-01-01)
Chuang, Pei-Yu
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Su, Shu-Hsuan
;
Chong, Cheong-Wei
;
Chen, Yi-Fan
;
Chou, Yu-Heng
Tuning the Fermi level (EF) in Bi2Te3 topological-insulator (TI) films is demonstrated on controlling the temperature of growth with molecular-beam epitaxy (MBE). Angle-resolved photoemission spectra (ARPES) reveal that EF of Bi2Te3 thin films shifts systematically with the growth temperature (Tg). The key role that a Bi-on-Te(1) (BiTe1) antisite defect plays in the electronic structure is identified through extended X-ray-absorption fine-structure (EXAFS) spectra at the Bi L-3-edge. Calculations of electronic structure support the results of fitting the EXAFS, indicating that the variation of EF is due to the formation and suppression of BiTe1 that is tunable with the growth temperature. Our findings provide not only insight into the correlation between the defect structure and electronic properties but also a simple route to control the intrinsic topological surface states, which could be useful for applications in TIbased advanced electronic and spintronic 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.