Browsing by Author "Lin, Chiung-Yuan"

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A study on NiGe-contacted Ge n(+)/p Ge shallow junction prepared by dopant segregation technique
(2015-05-01)
Tsui, Bing-Yue
;
Shih, Jhe-Ju
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Lin, Han-Chi
;
Lin, Chiung-Yuan
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電子工程學系及電子研究所
In this work, the effect of dopant segregation on the NiGe/n-Ge contact is studied by experiments and first-principles calculations. Both Al-contacted and NiGe-contacted n(+)/p junctions were fabricated. Phosphorus and arsenic ions were Implanted Before Germanide (IBG) formation or Implanted After Germanide (IAG) formation. The NiGe-contacted junction always exhibit higher forward current than the Al-contacted junction due to dopant segregation. First principles calculations predict that phosphorus atoms tend to segregate on both NiGe side and Ge side while arsenic atoms tend to segregate at Ge side. Since phosphorus has higher activation level and lower diffusion coefficient than arsenic, we propose a phosphorus IBG + arsenic IAG process. Shallow n(+)/p junction with junction depth 90 nm below the NiGe/Ge interface is achieved. The lowest and average contact resistivity is 2 x 10(-6) Omega cm(2) and 6.7 x 10(-6) Omega cm(2), respectively. Methods which can further reduce the junction depth and contact resistivity are suggested. (C) 2015 Elsevier Ltd. All rights reserved.
First Experimental Demonstration and Mechanism of Abnormal Palladium Diffusion Induced by Excess Interstitial Ge
(2018-11-01)
Chou, Chen-Han
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Shih, An-Shih
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Yu, Shao-Cheng
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Lin, Yu-Hsi
;
Tsai, Yi-He
This letter represents the first direct experimental demonstrations and mechanism proposal regarding abnormal palladium diffusion into germanium (Ge). Our experiments indicated that excess Ge atoms among palladium germanide alloy formation indirectly induce the abnormal out-diffusion of mass palladium atoms into Ge. Consequently, palladium germanide alloy on both n-type and p-type Ge form ohmic-like Schottky junctions. To identify this phenomenon, first-principle calculations and technology computer-aided design simulation were used to evaluate the electrical influence of palladium atoms in Ge. We discovered that the activated palladium atoms in Ge induce large midgap bulk-trap states, which contribute to a severe increment of trap-assisted tunneling current at the palladium germanide/Ge junction.
First-principles calculations of engineered surface spin structures
(2011-01-18)
Lin, Chiung-Yuan
;
Jones, B. A.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The engineered spin structures recently built and measured in scanning tunneling microscope experiments are calculated using density functional theory. By determining the precise local structure around the surface impurities, we find that the Mn atoms can form molecular structures with the binding surface, behaving like surface molecular magnets. The spin structures are confirmed to be antiferromagnetic, and the exchange couplings are calculated within 8% of the experimental values simply by collinear-spin generalized gradient approximation +U calculations. We can also explain why the exchange couplings significantly change with different impurity binding sites from the determined local structure. The bond polarity is studied by calculating the atomic charges with and without the Mn adatoms. In addition, we study a second adatom, Co. We study the surface Kondo effect of Co by calculating the surrounding local density of states and the on-site Coulomb U and compare and contrast the behavior of Co and Mn. Finally, our calculations confirm that the Mn and Co spins of these structures are 5/2 and 3/2, respectively, as also measured indirectly by scanning tunneling microscope.
First-principles Calculations on the Schottky Barrier Height of the NiGe/n-type Ge Contact with Dopant Segregation
(2014-01-01)
Lin, Han-Chi
;
Lin, Chiung-Yuan
;
Shih, Che-Ju
;
Tsui, Bing-Yue
;
電子工程學系及電子研究所
Effects of dopant segregation at the NiGe/Ge interface are analyzed theoretically and experimentally. First-principles calculations indicate that the physical Schottky barrier height would be reduced by the segregation of As by 0.081 eV. This small value is due to the Fermi-level pinning effect. Further improvement of the contact resistance may be achieved by reducing the interface states.
Hydrothermal crystallization and modification of surface hydroxyl groups of anodized TiO2 nanotube-arrays for more efficient photoenergy conversion
(2012-09-01)
Kuo, Yu-Yen
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Li, Tze-Huei
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Yao, Jing-Neng
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Lin, Chiung-Yuan
;
Chien, Chao-Hsin
This paper describes a crystallization method for anodized TiO2 nanotube-array using a hydrothermal process. Pre-sintered TiO2 nanotube-array could further crystallize without experiencing a collapse of the nanotubes under the hydrothermal environment. Applying the hydrothermal crystallization method, the transition of surface bonds of nanotube from Ti-O to Ti-OH/Ti-OH2 can be controlled by acidic hydrothermal pH levels. Dissolution and structural transformation of nanotubes was easily induced if the hydrothermal environment became basic. These effects depicted great influence on the anchoring of carboxylate groups on the surface of TiO2 nanotubes and affected the performance of the dye-sensitized solar cell utilizing the hydrothermally crystallized TiO2 nanotubes as the photoelectrode. The photoenergy conversion efficiency increased from 6.40% for thermally annealed nanotubes to 7.13% for hydrothermally crystallized ones under illumination of 100 rnW cm(-2). (C) 2012 Elsevier Ltd. All rights reserved.
Magnetic Interaction between Surface-Engineered Rare-Earth Atomic Spins
(2012-06-22)
Lin, Chiung-Yuan
;
Li, Jheng-Lian
;
Hsieh, Yao-Hsien
;
Ou, Keng-Liang
;
Jones, B. A.
We report the ab-initio study of rare-earth adatoms (Gd) on an insulating surface. This surface is of interest because of previous studies by scanning tunneling microscopy showing spin excitations of transition-metal adatoms. The present work is the first study of rare-earth spin-coupled adatoms, as well as the geometry effect of spin coupling and the underlying mechanism of ferromagnetic coupling. The exchange coupling between Gd atoms on the surface is calculated to be antiferromagnetic in a linear geometry and ferromagnetic in a diagonal geometry. We also find that the Gd dimers in these two geometries are similar to the nearest-neighbor and the next-nearest-neighbor Gd atoms in GdN bulk. We analyze how much direct exchange, superexchange, and Ruderman-Kittel-Kasuya-Yosida interactions contribute to the exchange coupling for both geometries by additional first-principles calculations of related model systems.
Tailoring thermopower of single-molecular junctions by temperature-induced surface reconstruction
(2012-12-10)
Hsu, Bailey C.
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Lin, Chiung-Yuan
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Hsieh, Yau-Shian
;
Chen, Yu-Chang
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電子物理學系
Recent experiments revealed that surface reconstruction occurs at around 300-400 K in the interface of C-60 adsorbed on Cu(111) substrate by scanning tunneling microscope techniques. To understand effects of such reconstruction on thermopower, we investigate the Seebeck coefficients of C-60 single-molecular junctions without and with surface reconstruction as a function of temperature at different tip-to-molecule heights from first-principles. Our calculations show that surface reconstruction can enhance or suppress Seebeck coefficients according to junctions at different tip heights. We further observe that the Seebeck coefficient of the junction at d = 3.4 angstrom may change from p- to n-type under surface reconstruction. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769814]