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RISS 인기검색어
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- 저자 : Yuehua Dai (검색결과 2 건)
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Effect of Graphene/TiO2 (001) Interface on Threshold Voltage and Nonlinearity
Yuehua Dai,Shanshan Gong,Zhisheng Zhong,Fengyu Gao,Feifei Wang,Cheng Ding,Jin Yang,Fei Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.6
In this work, the threshold voltage (Vth) and nonlinearity (NL) of Graphene (Gra)/TiO2/Gra heterojunction were studied. First, the density functional tight binding (DFTB+) and much more dynamics were used to investigate the IV curves and the resistive switching properties of TiO2 slab and Gra/TiO2/Gra heterojunction. The NL of Gra/TiO2/Gra heterojunction is stronger than that of the TiO2 slab. The Vth of the resistive transition of the heterojunction is larger than that of the TiO2 slab. The tunneling probabilities and the Mulliken atomic population at the Gra/TiO2 interface under different electric fields were calculated by the Cambridge sequential total energy package (CASTEP). Results showed that both the parameters evidently increased under a certain numerical electric field. Finally, the movement of atom in the electric field and the change in the chemical bond were simulated by DFTB+ module. The effect of the Gra/TiO2 interface on Vth and NL was further illustrated. Postponed Vth and improved NL were found at the heterojunction relative to the TiO2 slab due to the presence of the interface barrier. This work provides guidance and reference for design and optimization of TiO2-based selectors.
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Study of the Non-Linearity on TiO2(0 0 1) Surface with Oxygen Defects: A First-Principles Study
Yuehua Dai,Xu Zhang,Chengzhi Ma,Zhiyong Pan,Feifei Wang,Wenjuan Lu,Jin Yang,Fei Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.8
First-principles plane-wave pseudopotential calculations were performed to study the energetics and electronic structures of oxygen defects on rutile TiO2(0 0 1). The influence of the material thickness on non-linearity (NL) was studied. With the increase in the thickness, the NL became stronger. Calculating the site-projected density of states by applying an external electric field showed that the NL of the bulk is due to the exchange of electrons between O 2p orbitals and Ti 3d orbitals. Finally, the influence of oxygen defects—oxygen vacancies (Vo), oxygen interstitials (Oi), and oxygen vacancies/oxygen interstitial (Vo + Oi) pairs (Frenkel pair defects)—on the NL of TiO2 was studied. These results demonstrate that the band gap (Eg) of TiO2 became gradually narrower as the electric field increased. The Stark effect and defects can lead to the splitting of degenerate energy levels. Stronger electric fields increase the band splitting and reduce Eg. With the increase in the Vo concentration, the decrease in the splitting amplitude and width of the energy level lead to weakening of the transfer of electrons between O and Ti atoms and optimizing the NL of TiO2. Therefore, the incorporation of Vo plays a significant role in improving the NL of TiO2.
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