33 results on '"Chii-Bin Wu"'
Search Results
2. Temperature-dependent charge-carrier transport between Si-δ-doped layers and AlGaAs/InGaAs/AlGaAs quantum well with various space layer thicknesses measured by Hall-effect analysis
- Author
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Victor Chien-Pin Lu, Jyh-Shyang Wang, Kuan-Cheng Chiu, Ji-Lin Shen, Chii-Bin Wu, and Wilson Yeung-Sy Su
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010302 applied physics ,Electron mobility ,Multidisciplinary ,Materials science ,Condensed matter physics ,Dopant ,Electronics, photonics and device physics ,Doping ,lcsh:R ,lcsh:Medicine ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,01 natural sciences ,Article ,Hysteresis ,Nanoscale devices ,Hall effect ,0103 physical sciences ,Charge carrier ,lcsh:Q ,Condensed-matter physics ,0210 nano-technology ,lcsh:Science ,Quantum well - Abstract
Temperature (T = 40 ~ 300 K) dependence of Hall-effect analysis on the dual Si-δ-doped AlGaAs/InGaAs/AlGaAs quantum-well (QW) structures with various space layer thicknesses (tS = 5, 10 and 15 nm) was performed. An interesting hysteresis behavior of electron sheet concentration [n2D(T)] was observed for tS = 10 and 15 nm but not for tS = 5 nm. A model involving two different activation barriers encountered respectively by electrons in the active QW and by electrons in the δ-doped layers is proposed to account for the hysteresis behavior. However, for small enough tS (= 5 nm ≤ 2.5 s, where s = 2.0 nm is the standard deviation of the Gaussian fit to the Si-δ-doped profile), the distribution of Si dopants near active QW acted as a specific form of “modulation doping” and can not be regarded as an ideal δ-doping. These Si dopants nearby the active QW effectively increase the magnitude of n2D, and hence no hysteresis curve was observed. Finally, effects from tS on the T-dependence of electron mobility in active QW channel are also discussed.
- Published
- 2020
3. Enhanced photoluminescence of InGaAs/AlGaAs quantum well with tungsten disulfide quantum dots
- Author
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Svette Reina Merden Santiago, Cheng-Ying Chen, Kuan-Cheng Chiu, Wilson Yeung-Sy Su, Chih-Yang Huang, Ji-Lin Shen, Chii-Bin Wu, Jyh-Shyang Wang, and Chia-Cheng Chiang Hsieh
- Subjects
Photoluminescence ,Materials science ,Tungsten disulfide ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Band diagram ,General Materials Science ,Electrical and Electronic Engineering ,Quantum well ,Kelvin probe force microscope ,business.industry ,Mechanical Engineering ,Heterojunction ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,Quantum dot ,Diethylenetriamine ,Optoelectronics ,0210 nano-technology ,business - Abstract
The pristine and diethylenetriamine (DETA)-doped tungsten disulfide quantum dots (WS2 QDs) with an average lateral size of about 5 nm have been synthesized using pulsed laser ablation (PLA). Introduction of the synthesized WS2 QDs on the InGaAs/AlGaAs quantum wells (QWs) can improve the photoluminescence (PL) of the InGaAs/AlGaAs QW as high as 6 fold. On the basis of the time-resolved PL and Kelvin probe measurements, the PL enhancement is attributed to the carrier transfer from the pristine or DETA-doped WS2 QDs to the InGaAs/AlGaAs QW. A heterostructure band diagram is proposed for explaining the carrier transfer, which increases the hole densities in the QW and enhances its PL intensity. This study is expected to be beneficial for the development of the InGaAs-based optoelectronic devices.
- Published
- 2020
4. Magneto optical Kerr effect measurement with pulsed magnetic field
- Author
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Chii-Bin Wu, Yi-Kai Liao, and Sih-Ying Lin
- Subjects
Physics ,Electromagnet ,business.industry ,Oersted ,General Physics and Astronomy ,Pulse duration ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Magnetic field ,Capacitor ,Optics ,Magnetic core ,Magneto-optic Kerr effect ,law ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,business - Abstract
With a controllable discharge of capacitors to coils, a series of positive and negative magnetic field pulses has been generated and was used to perform the magneto optical Kerr effect (MOKE) measurement on a Fe film. The realized maximum magnetic field strength is around one thousand oersteds and the pulse duration is around 1 ms. The total MOKE response is taken within 4 ms. This technique can be applied when a moderate magnetic field is needed but a strong electromagnet with iron core is not available or not suitable.
- Published
- 2017
5. Time dependence of negative and positive photoconductivity for Si δ-doped AlGaAs/InGaAs/AlGaAs quantum well under various temperatures and various incident photon energies and intensities
- Author
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Ching Wang, Chun-Yi Li, Wilson Yeung-Sy Su, Chii-Bin Wu, Ji-Lin Shen, Jyh-Shyang Wang, Bu-Wei Huang, Kuan-Cheng Chiu, and Chih-Ting Chen
- Subjects
Photon ,Materials science ,Mechanical Engineering ,Photoconductivity ,Doping ,Bioengineering ,02 engineering and technology ,General Chemistry ,Trapping ,Electron ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Spectral line ,0104 chemical sciences ,Photoexcitation ,Mechanics of Materials ,General Materials Science ,Electrical and Electronic Engineering ,Atomic physics ,0210 nano-technology ,Quantum well - Abstract
Si δ-doped AlGaAs/InGaAs/AlGaAs quantum well (QW) structure is commonly adopted as one of the core elements in modern electric and optoelectronic devices. Here, the time dependent photoconductivity spectra along the active InGaAs QW channel in a dual and symmetric Si δ-doped AlGaAs/InGaAs/AlGaAs QW structure are systematically studied under various temperatures (T = 80–300 K) and various incident photon energies (E in = 1.10–1.88 eV) and intensities. In addition to positive photoconductivity, negative photoconductivity (NPC) was observed and attributed to two origins. For T = 180–240 K with E in = 1.51–1.61 eV, the trapping of the photo-excited electrons by the interface states located inside the conduction band of InGaAs QW layer is one of the origins for NPC curves. For T = 80–120 K with E in = 1.10–1.63 eV, the photoexcitation of the excess ‘supersaturated’ electrons within the active InGaAs QW caused by the short cooling process is another origin.
- Published
- 2021
6. Tuning the Electronic Properties of Rotated Graphene on Ni(111) by Nickel Carbide Intercalation
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Chii-Bin Wu, Matthias Bernien, Wolfgang Kuch, and Jiaming Song
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Superlattice ,Intercalation (chemistry) ,chemistry.chemical_element ,02 engineering and technology ,01 natural sciences ,law.invention ,Optics ,law ,0103 physical sciences ,Physical and Theoretical Chemistry ,010306 general physics ,Spectroscopy ,Local density of states ,Condensed matter physics ,Chemistry ,business.industry ,Graphene ,Biasing ,021001 nanoscience & nanotechnology ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,Scanning tunneling microscope ,0210 nano-technology ,business ,Carbon - Abstract
High-temperature-deposited rotated graphene (Gr) on Ni(111) has been investigated by in situ scanning tunneling microscopy and spectroscopy at room temperature. The rotated Gr exhibits weak bonding to the Ni(111) surface, which facilitates formation of Ni2C or a second Gr layer underneath via bulk carbon segregation. Areas of rotated Gr present a bias voltage dependence of the apparent amplitude of Gr superlattice corrugations. We find that Ni2C underneath rotated Gr introduces additional electronic features that vary with the gap resistance, which could be related to an orientation-dependent interaction between Ni2C and Gr. Furthermore, the exposure to oxygen has a significant influence on the local density of states of Gr/Ni2C, other than on Ni(111) covered with nonrotated Gr.
- Published
- 2016
7. The reduction of antiphase boundary defects by the surfactant antimony and its application to the III–V multi-junction solar cells
- Author
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Jung-Ting Chang, Chih-Hung Wu, Shih-Chang Tong, Chii-Bin Wu, Pai-Chun Wei, and Jyh-Shyang Wang
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010302 applied physics ,Materials science ,Photoluminescence ,Renewable Energy, Sustainability and the Environment ,Open-circuit voltage ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Pulmonary surfactant ,Antimony ,chemistry ,0103 physical sciences ,symbols ,0210 nano-technology ,Raman spectroscopy ,Short circuit ,Diode - Abstract
The CuPtB ordering and the antiphase boundaries (APBs) in GaInP2 epifilms were found to be diminished by the addition of the surfactant antimony (Sb) during the epitaxy. This is evidenced by the disappearance of the APBs related deep level peak in the Raman and photoluminescence (PL) spectra, as well as the significantly increased lifetime of the minority carriers. The GaInP2/metamorphic (MM)-GaInAs/Ge multi-junction solar cells made by this method possess enhanced short circuit current density and show a narrower distribution of the open circuit voltage. We believe the use of surfactant Sb to control APBs during the growth of InGaP2 would be very useful for designing GaInP2-based devices, such as solar cells, laser diodes and light-emitting diodes.
- Published
- 2016
8. Surface morphology, magnetism and chemical state of Fe coverage on MoS2 substrate
- Author
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Venkata Ramana Mudinepalli, Po Chun Chang, Kai Lin Hsu, Wen Chin Lin, Hung Chang Hsu, Chii Bin Wu, and Tsu Yi Fu
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Materials science ,Condensed matter physics ,Photoemission spectroscopy ,Analytical chemistry ,General Physics and Astronomy ,Nanoparticle ,Substrate (chemistry) ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Surfaces, Coatings and Films ,law.invention ,Chemical state ,chemistry.chemical_compound ,chemistry ,X-ray photoelectron spectroscopy ,law ,Particle size ,Scanning tunneling microscope ,Molybdenum disulfide - Abstract
The surface morphology, magnetism and chemical state of Fe coverage on the surface of molybdenum disulfide (MoS2) were investigated using scanning tunneling microscopy, magneto-optical Kerr effect, and depth-profiling X-ray photoemission spectroscopy (XPS). Fe deposition on the MoS2 substrate resulted in a nanoparticle array with the particle size ranged few nanometers (∼3±1 nm). For low-coverage Fe deposition
- Published
- 2015
9. Density-Dependent Carrier Recombination in MoS2 Quantum Dots and Its Implications for Luminescence Sensing of Ammonium Hydroxide.
- Author
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Santiago, Svette Reina Merden S., Hong-Jyun Wang, Yu-Ting Chen, I-Jen Hsu, Chii-Bin Wu, Kai-Mao Hsu, Min-Chiang Cheng, Tzu-Neng Lin, Feria, Denice N., Wu-Ching Chou, and Ji-Lin Shen
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- 2020
- Full Text
- View/download PDF
10. Tailoring interlayer coupling and coercivity in Co/Mn/Co trilayers by controlling the interface roughness.
- Author
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Bin Zhang, Chii-Bin Wu, and Kuch, Wolfgang
- Subjects
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COERCIVE fields (Electronics) , *INTERFACIAL roughness , *KERR magneto-optical effect , *ANTIFERROMAGNETIC materials , *MONOMOLECULAR films - Abstract
Epitaxial Co/Mn/Co trilayers with a wedged Mn layer were grown on Cu(001) and studied by magneto-optical Kerr effect measurements. The bottom Co film as well as the Mn film exhibits a layer-by-layer growth mode, which allows to modify both interface roughnesses on the atomic scale by tuning the thicknesses of the films to achieve a certain filling of their topmost atomic layers. The onset of antiferromagnetic order in the Mn layer at room temperature was found at thicknesses of 4.1 (4.8) and 3.4 (4.0) atomic monolayers (ML) for a filled (half-filled) topmost atomic layer of the bottom Co film in Mn/Co bilayers and Co/Mn/Co trilayers, respectively. Magnetization loops with only one step were found for a trilayer with half-filled topmost atomic layer of the bottom Co film, while loops with two separate steps have been observed in trilayers with an integer number of atomic layers in the bottom Co film. The coercivity of the top Co film shows an oscillation with 1 ML period as a function of the Mn thickness above 10 ML, which is interpreted as the influence of the atomic-scale control of the interface roughness on the interface exchange coupling between the antiferromagnetic Mn and the top ferromagnetic (FM) Co layer. The strength of the magnetic interlayer coupling between the top and bottom Co layers through the Mn layer for an integer number of atomic layers in the bottom Co layer, deduced from minor-loop measurements, exhibits an oscillation with a period of 2 ML Mn thickness, indicative of direct exchange coupling through the antiferromagnetic Mn layer. In addition, a long-period interlayer coupling of the two FM layers with antiparallel coupling maxima at Mn thicknesses of 2.5, 8.2, and 13.7 ML is observed and attributed to indirect exchange coupling of the Rudermann-Kittel- Kasuya-Yosida type. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
11. Controllable sealing of leaky alumina films on NiAl(100) surface by catalytic oxidation.
- Author
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Kuan-Te Liu, Jian-Wei Chen, Yu-Wen Liao, Wen-Chin Lin, Chii-Bin Wu, Chien-Cheng Kuo, Minn-Tsong Lin, and Ker-Jar Song
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OXIDE coating ,CATALYTIC oxidation ,COBALT ,NANOPARTICLES ,OXIDATION - Abstract
We show the oxide films grown by saturated dosing of oxygen on NiAl(100) is leaky, i.e., it has no apparent effect blocking deposited Co from diffusion into the bulk. We then show the easy paths for diffusion (presumably the boundaries between the oxide stripes) can be sealed by an oxidation process catalyzed by Co nanoparticles. Once sealed, the temperature range in which Co nanoparticles persist on the surface is extended by 400K (up to 1100K). Such "leak tight" oxide films could serve as better corrosion barrier and insulting layers. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
12. Layer-dependent properties and noncollinear spin structure of epitaxial antiferromagnetic Mn films onCo/Cu(001)
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Chii-Bin Wu, Bin Zhang, Wolfgang Kuch, Jianli Xu, and Jiaming Song
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Materials science ,Condensed matter physics ,Scanning tunneling spectroscopy ,Substrate (electronics) ,Spin structure ,Condensed Matter Physics ,Atomic units ,Electronic, Optical and Magnetic Materials ,law.invention ,Condensed Matter::Materials Science ,Tetragonal crystal system ,Ferromagnetism ,law ,Antiferromagnetism ,Scanning tunneling microscope - Abstract
The surface of expanded face-centered tetragonal antiferromagnetic Mn films of a few atomic monolayers thickness grown epitaxially on $\mathrm{Co}/\mathrm{Cu}(001)$ was investigated at room temperature by scanning tunneling microscopy and scanning tunneling spectroscopy using a ferromagnetic ring-shaped bulk iron probe. We show that the main contribution to the contrast modulation observed as a function of Mn thickness in differential conductance maps is not due to spin-polarized tunneling from a layerwise antiferromagnetic spin alignment. Instead, it is mainly of electronic origin resulting from layer-dependent electronic properties of the Mn film, probably related to different levels of intermixing with Co atoms. On the atomic scale, the Mn surface demonstrates a geometrical reconstruction with a $(12\ifmmode\times\else\texttimes\fi{}2)$ periodicity in two orthogonal domains on the fourfold symmetric substrate with an apparent surface corrugation of up to 0.3 \AA{}. Simultaneously recorded differential conductance maps show different textures in the two orthogonal domains, providing evidence for noncollinearity in the Mn surface spin structure.
- Published
- 2015
13. Influence of NixMn1−x thickness and composition on the Curie temperature of Ni in NixMn1−x/Ni bilayers on Cu3Au(001)
- Author
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Chii-Bin Wu, D. Schiestl, Mustafa Erkovan, Wolfgang Kuch, and Yasser A. Shokr
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Materials science ,Kerr effect ,Condensed matter physics ,Curie temperature ,Composition (visual arts) ,Condensed Matter Physics ,Epitaxy ,Chemical composition ,Layer (electronics) ,Layer thickness ,Electronic, Optical and Magnetic Materials ,Overlayer - Abstract
We present a magneto-optical Kerr effect study of epitaxial bilayers consisting of Ni and NixMn1−x on Cu3Au(001). The bottom Ni layer, the NixMn1−x layer thickness and its chemical composition were changed and the Curie temperature of the system was determined. We focused on two different regimes of NixMn1−x composition, namely a Mn-rich with x between 0.25 and 0.5, and a Ni-rich with x around 0.7. In these two composition ranges, a NixMn1−x overlayer exhibits a different effect on the Curie temperature of the Ni layer. While Mn-rich NixMn1−x layers reduce the Curie temperature of the Ni underlayer, Ni-rich NixMn1−x layers enhance the Curie temperature with respect to the pure Ni film. This is attributed to changes in the effective thickness of the Ni layer by exchange interactions with the NixMn1−x overlayer.
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- 2015
14. Pinned magnetic moments in exchange bias
- Author
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Wolfgang Kuch, Chii-Bin Wu, and Yaqoob M. Khan
- Subjects
Physics ,Magnetization ,Magnetic anisotropy ,Exchange bias ,Ferromagnetism ,Condensed matter physics ,Magnetic moment ,Antiferromagnetism ,Spin structure ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Spin-½ - Abstract
Magneto-optical Kerr effect measurements of epitaxial AFM/FM bilayers and FM/AFM/FM trilayers on ${\mathrm{Cu}}_{3}$Au(001), where ``AFM'' stands for a Ni${}_{25}$Mn${}_{75}$ antiferromagnetic layer, and ``FM'' for ferromagnetic layers that are either Ni or Ni/Co with out-of-plane or in-plane easy axis of magnetization, show that trilayers with collinear magnetization directions of both FM layers exhibit always a much lower exchange bias field ${H}_{\mathrm{eb}}$ at a fixed temperature compared to bilayers of the same Ni${}_{25}$Mn${}_{75}$ thickness. At the same time, the blocking temperature for exchange bias ${T}_{b}$ is strongly reduced. In trilayers with orthogonal easy axes of the two FM layers (in-plane and out-of-plane), in contrast, both ${H}_{\mathrm{eb}}$ and ${T}_{b}$ are nearly identical to that of the corresponding bilayers. Such a behavior can be explained by pinned magnetic moments inside the bulk of the AFM layer that coexist independently for orthogonal spin directions, but have to be equally shared between both interfaces in the case of collinear spin directions. This result thus also confirms a 3Q-like noncollinear spin structure of Ni${}_{25}$Mn${}_{75}$.
- Published
- 2014
15. Probing antiferromagnetism in NiMn/Ni/(Co)/Cu3Au(001) single-crystalline epitaxial thin films
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M. Yaqoob Khan, Wolfgang Kuch, Chii-Bin Wu, and Mustafa Erkovan
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Condensed Matter::Materials Science ,Materials science ,Kerr effect ,Magnetic structure ,Ferromagnetism ,Condensed matter physics ,Proximity effect (audio) ,Monolayer ,General Physics and Astronomy ,Antiferromagnetism ,Thin film ,Coercivity - Abstract
Antiferromagnetism of equi-atomic single-crystalline NiMn thin film alloys grown on Ni/Cu3Au (001) is probed by means of magneto-optical Kerr effect (MOKE). Thickness-dependent coercivity (HC) enhancement of polar MOKE measurements in NiMn/Ni/Cu3Au(001) shows that ~7 atomic monolayers (MLs) NiMn order antiferromagnetically at room temperature. It is found that NiMn can couple to out-of-plane (OoP) as well as in-plane (IP) magnetized Ni films, the latter stabilized by Co under-layer deposition. The antiferromagnetic (AFM) ordering temperature (TAFM) of NiMn coupled to OoP Ni is found to be much higher (up to 110K difference) than in the IP case, for similar interfacial conditions. This is attributed to a magnetic proximity effect in which the ferromagnetic (FM) layer substantially influences TAFM of the adjacent AFM layer, and can be explained by either (i) a higher interfacial coupling strength and/or (ii) a thermally more stable NiMn spin structure when coupled to Ni magnetized in OoP direction than in IP. An exchange-bias effect could only be observed for the thickest NiMn film studied (35.7 ML); the exchange- bias field is higher in the OoP exchange-coupled system than in the IP one, possibly due to the same reason/s.
- Published
- 2013
16. Layered antiferromagnetic spin structures of expanded face-centered-tetragonal Mn(001) as an origin of exchange bias coupling to the magnetic Co layer
- Author
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Chii Bin Wu, Pin-Jui Hsu, Lun Jia Chen, Minn-Tsong Lin, Sheng Syun Wong, Yu Hsun Chu, Bo-Yao Wang, and Chun-I Lu
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Materials science ,Condensed matter physics ,Spins ,media_common.quotation_subject ,Frustration ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Tetragonal crystal system ,Magnetic anisotropy ,Exchange bias ,Domain wall (magnetism) ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,Spin (physics) ,media_common - Abstract
Spin structures of an exchange-coupled-bilayer system of expanded-face-centered-tetragonal (e-fct) Mn(001) ultrathin films grown on Co/Cu(001) were resolved by means of spin-polarized scanning-tunneling microscopy. With an in-plane spin-sensitive probe, a layered antiferromagnetic-spin ordering of Mn overlayers was evidenced directly. In addition, the spin frustration across the same Mn layer creating a narrow domain wall down to nanometer scale was also observed along the buried step of Co underlayers. According to the micromagnetic simulation, the step-induced domain-wall width is in agreement with the experimental results. Such in-plane layered antiferromagnetic-spin structures of e-fct Mn(001) provide uncompensated spins at the interface with Co underlayers and elucidate the mechanism of the corresponding exchange-bias field observed in the previous studies.
- Published
- 2012
17. Nanopatterning of magnetic domains: Fe coverage of self-assembled alumina nanostructure
- Author
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Minn-Tsong Lin, Zheng Gai, Bo-Yao Wang, Wen Chin Lin, and Chii Bin Wu
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Nial ,Nanostructure ,Materials science ,Magnetic domain ,Scanning electron microscope ,General Engineering ,General Physics and Astronomy ,Nanoparticle ,Nanotechnology ,Micrometre ,Paramagnetism ,Ferromagnetism ,computer ,computer.programming_language - Abstract
Nanosized ultrathin magnetic films were prepared by controlling the deposition of Fe onto an oxidized NiAl(001) surface with an alumina nanostructure on it. Because the ultrathin ferromagnetic Fe films on the bare NiAl(001) surface are separated by paramagnetic Fe nanoparticles on the alumina stripes, as determined by scanning electron microscopy with spin analysis, they form rectangular domains with sizes ranging from tens of nanometer to larger than a micrometer. Magnetic domain patterning can thus be achieved by controlling the Fe coverage and nanostructured template.
- Published
- 2015
18. Temperature-induced sign change of the magnetic interlayer coupling in Ni/Ni25Mn75/Ni trilayers on Cu3Au(001)
- Author
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Chii-Bin Wu, Oliver Sandig, Mustafa Erkovan, Bin Zhang, Wolfgang Kuch, and Yasser A. Shokr
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Materials science ,Kerr effect ,RKKY interaction ,Condensed matter physics ,General Physics and Astronomy ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter::Materials Science ,Magnetization ,Exchange bias ,Ferromagnetism ,Condensed Matter::Superconductivity ,Monolayer ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,Néel temperature - Abstract
We investigated the magnetic interlayer coupling between two ferromagnetic (FM) Ni layers through an antiferromagnetic (AFM) Ni 25Mn75 layer and the influence of this coupling on the exchange bias phenomenon. The interlayer coupling energy of an epitaxial trilayer of 14 atomic monolayers (ML) Ni/45 ML Ni 25Mn75/16 ML Ni on Cu3Au(001) was extracted from minor-loop magnetization measurements using in-situ magneto-optical Kerr effect. The interlayer coupling changes from ferromagnetic to antiferromagnetic when the temperature is increased above 300 K. This sign change is interpreted as the result of the competition between an antiparallel Ruderman-Kittel-Kasuya-Yosida (RKKY)-type interlayer coupling, which dominates at high temperature, and a stronger direct exchange coupling across the AFM layer, which is present only below the Néel temperature of the AFM layer.
- Published
- 2015
19. Controllable sealing of leaky alumina films on NiAl(100) surface by catalytic oxidation
- Author
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Wen Chin Lin, Ker Jar Song, Jian Wei Chen, Minn-Tsong Lin, C. C. Kuo, Kuan Te Liu, Yu Wen Liao, and Chii Bin Wu
- Subjects
Surface diffusion ,Nial ,Materials science ,Diffusion ,Metallurgy ,Oxide ,General Physics and Astronomy ,Nanoparticle ,Corrosion ,chemistry.chemical_compound ,Catalytic oxidation ,chemistry ,Chemical engineering ,Thin film ,computer ,computer.programming_language - Abstract
We show the oxide films grown by saturated dosing of oxygen on NiAl(100) is leaky, i.e., it has no apparent effect blocking deposited Co from diffusion into the bulk. We then show the easy paths for diffusion (presumably the boundaries between the oxide stripes) can be sealed by an oxidation process catalyzed by Co nanoparticles. Once sealed, the temperature range in which Co nanoparticles persist on the surface is extended by 400 K (up to 1100 K). Such “leak tight” oxide films could serve as better corrosion barrier and insulting layers.
- Published
- 2014
20. Soft perpendicular magnetization and spin reorientation transition of Fe films on NiAl(001)
- Author
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Chii Bin Wu, Wei Shu Li, Zheng Yuan Huang, Wen Chin Lin, Minn-Tsong Lin, Yin Chih Lin, and Ying Chin Chen
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Nial ,Materials science ,Condensed matter physics ,Plane (geometry) ,General Engineering ,General Physics and Astronomy ,Coercivity ,Condensed Matter::Materials Science ,Magnetic anisotropy ,Monolayer ,Phenomenological model ,Perpendicular ,Anisotropy ,computer ,computer.programming_language - Abstract
Ultrathin Fe films were deposited on NiAl(001) for studies of their magnetic properties and crystalline structures. Thickness-driven perpendicular to in-plane spin reorientation transition was observed at a thickness of ~4 monolayers (MLs) at room temperature without structural variation. At less than the critical thickness, the Fe film's easy axis is perpendicular to the surface plane with a small coercive field (Hc ≈ 1 Oe), which was much smaller than that of other systems with perpendicular anisotropy. The Fe/NiAl(001) system revealed an extremely soft perpendicular magnetization. At more than the critical thickness, the easy axis lays in the surface plane. The magnetic anisotropy terms were calculated and discussed through a phenomenological model. The weaker surface anisotropy might be attributed to the reconstructed NiAl(001) surface.
- Published
- 2014
21. Concentration- and thickness-dependent magnetic properties of NixMn100−xin epitaxially grown NixMn100−x/Ni/(Co/)Cu3Au(001)
- Author
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Chii-Bin Wu, Stefanie K. Kreft, Wolfgang Kuch, and M. Yaqoob Khan
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Magnetic anisotropy ,Magnetization ,Materials science ,Domain wall (magnetism) ,Kerr effect ,Exchange bias ,Condensed matter physics ,Antiferromagnetism ,General Materials Science ,Spin structure ,Condensed Matter Physics ,Epitaxy - Abstract
Magnetic proximity effects in single-crystalline NixMn100?x/Ni(/Co) bilayers on Cu3Au(001) are investigated for in-plane (IP) and out-of-plane (OoP) magnetization by means of the longitudinal and polar magneto-optical Kerr effect. Attention is paid to the influence on concentration- and thickness-dependent antiferromagnetic ordering (TAFM) and blocking (Tb) temperatures as well as the exchange bias field (Heb). For all the NixMn100?x films under study in contact with IP Ni, increasing TAFM is observed with decreasing Ni concentration from ?50 to ?20%, whereas only a slight change in TAFM is observed for the OoP case. Between ?28% and ?35% Ni concentration, a crossover temperature exists below which TAFM for the IP samples is higher than for the OoP samples and vice versa. Tb is higher for the IP case than for OoP, except for an equi-atomic NiMn film, while Heb increases significantly for both magnetization directions with decreasing x. These results are attributed to: (i)?a rotation of the non-collinear 3Q-like spin structure of NixMn100?x from the more-OoP to the more-IP direction for decreasing Ni concentration x, along with an associated increased magnetic anisotropy, and (ii)?a smaller domain wall width within the NixMn100?x films at smaller x, leading to a smaller thickness required to establish exchange bias at a fixed temperature.
- Published
- 2013
22. Spin-polarized scanning tunneling microscopy study of Mn/Co/Cu(001) using a bulk Fe ring probe
- Author
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Chii-Bin Wu, Jiaming Song, and Wolfgang Kuch
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Materials science ,Physics and Astronomy (miscellaneous) ,Magnetic structure ,Analytical chemistry ,chemistry.chemical_element ,Spin polarized scanning tunneling microscopy ,Manganese ,Copper ,law.invention ,Crystallography ,chemistry ,law ,Monolayer ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,Scanning tunneling microscope ,Spin (physics) - Abstract
A bulk ring probe made of pure iron wire with diameter of 0.125mm was prepared for spin-polarized scanning tunneling microscopy at room temperature in ultrahigh vacuum. The layerwise antiferromagnetic spin contrast of 2.8 atomic monolayers (ML) Mn/4.5 ML Co/Cu (001) observed with such a probe revealed a spin asymmetry of 14% and a signal-to-noise ratio of 1.8. Areas of reversed spin contrast on the same atomic layer of Mn were observed and attributed to the influence from underlying Co steps and islands. This demonstrates the simplicity of preparation and capability of such bulk Fe ring probes.
- Published
- 2012
23. Coverage dependence of magnetic domain structure and magnetic anisotropy in supported Fe nanoparticles on Al2O3/NiAl(100)
- Author
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Minn-Tsong Lin, Zheng Gai, Hong Yu Yen, Wen Chin Lin, Lan Gao, Pin-Jui Hsu, J. Shen, and Chii Bin Wu
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Materials science ,Condensed matter physics ,Magnetic structure ,Magnetic domain ,Magnetism ,General Physics and Astronomy ,Magnetic hysteresis ,law.invention ,Crystallography ,Magnetic anisotropy ,law ,Magnetic nanoparticles ,Scanning tunneling microscope ,Anisotropy - Abstract
Studies of magnetic domain and magnetic anisotropy in collected nanoparticles are crucial for both understanding interparticle interaction and engineering in applications. In order to characterize the microscopic surface morphology and the nanoscale magnetic domain structure of Fe nanoparticles, a scanning tunneling microscope and a scanning electron microscope with polarization analysis (SEMPA) were used in our experiment. For the coverage of 9–13 monolayers (MLs) Fe deposited on Al2O3/NiAl(100), circular and well-separated nanoparticles were grown. As the coverage increased up to 23–33 ML, these Fe nanoparticles started to coalesce and form elongated islands. Therefore a transition from isotropic to anisotropic in-plane magnetism was observed. Our proposed uniaxial magnetic anisotropy models effectively explain the azimuthal angle dependent two-step hysteresis loops. Moreover, the in situ measured SEMPA images clearly show the coverage dependent evolution of magnetic domain structure. Variations in inte...
- Published
- 2010
24. Layer-dependent properties and noncollinear spin structure of epitaxial antiferromagnetic Mn films on Co/Cu(001).
- Author
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Jiaming Song, Chii-Bin Wu, Bin Zhang, Jianli Xu, and Kuch, Wolfgang
- Subjects
- *
ANTIFERROMAGNETIC materials , *THIN films , *EPITAXY , *SCANNING tunneling microscopy , *FERROMAGNETIC materials - Abstract
The surface of expanded face-centered tetragonal antiferromagnetic Mn films of a few atomic monolayers thickness grown epitaxially on Co/Cu(001) was investigated at room temperature by scanning tunneling microscopy and scanning tunneling spectroscopy using a ferromagnetic ring-shaped bulk iron probe. We show that the main contribution to the contrast modulation observed as a function of Mn thickness in differential conductance maps is not due to spin-polarized tunneling from a layerwise antiferromagnetic spin alignment. Instead, it is mainly of electronic origin resulting from layer-dependent electronic properties of the Mn film, probably related to different levels of intermixing with Co atoms. On the atomic scale, the Mn surface demonstrates a geometrical reconstruction with a (12 × 2) periodicity in two orthogonal domains on the fourfold symmetric substrate with an apparent surface corrugation of up to 0.3 Å. Simultaneously recorded differential conductance maps show different textures in the two orthogonal domains, providing evidence for noncollinearity in the Mn surface spin structure. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
25. Electronically patterning through one-dimensional nanostripes with high density of states on single-crystalline Al2O3 domain
- Author
-
Sheng Syun Wong, Hong Yu Yen, Minn-Tsong Lin, Wen Chin Lin, Pin-Jui Hsu, and Chii Bin Wu
- Subjects
Materials science ,Nanostructure ,Physics and Astronomy (miscellaneous) ,Band gap ,business.industry ,Oxide ,Nucleation ,Nanoparticle ,Nanotechnology ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Density of states ,Optoelectronics ,Scanning tunneling microscope ,business ,Spectroscopy - Abstract
Self-assembled one-dimensional nanostripes on the single-crystalline Al2O3 domains are found to be the nucleation sites of nanoparticles through an enhanced density of states observed by the scanning tunneling microscopy and spectroscopy. Bias-dependent topographic images and the conductivity spectra indicate that these nanostripes have both enhanced occupied and unoccupied states within the oxide bandgap. These more metallic nanostripes have stronger electronically trapping ability than the oxide domain, which can be used as a one-dimensional electronically self-patterned template for the guided growth of nanostructures.
- Published
- 2008
26. Using ring-shaped and magnetically coated tungsten wire as the probe of spin-polarized scanning tunneling microscopy
- Author
-
Pin-Jui Hsu, Minn-Tsong Lin, Hong-Yu Yen, and Chii-Bin Wu
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Scanning tunneling spectroscopy ,Spin polarized scanning tunneling microscopy ,Scanning capacitance microscopy ,Electrochemical scanning tunneling microscope ,law.invention ,Optics ,Magneto-optic Kerr effect ,law ,Optoelectronics ,Scanning tunneling microscope ,business ,Non-contact atomic force microscopy ,Vibrational analysis with scanning probe microscopy - Abstract
We report a method of magnetic probe fabrication using ring-shaped and iron-coated tungsten wire for spin-polarized scanning tunneling microscopy. Magneto-optic Kerr effect measurement on the probe front end shows that by controlling the saturating field direction, we can fix the probe magnetization in the specific in-plane direction. The ring is applied to the scanning tunneling microscopy and spectroscopy experiment on 6.8 ML Mn∕Fe(001), and spin contrast in the in-plane direction is demonstrated.
- Published
- 2007
27. Controlled growth of Co nanoparticle assembly on nanostructured template Al2O3∕NiAl(100)
- Author
-
Bin Rui Xu, Wen Chin Lin, Minn-Tsong Lin, Hong Yu Yen, Shen Shing Wong, Chii Bin Wu, Cheng-Tien Chiang, and Po Chun Huang
- Subjects
Aluminium oxides ,Nial ,Nanostructure ,Materials science ,Physics and Astronomy (miscellaneous) ,Annealing (metallurgy) ,Metallurgy ,Nanoparticle ,Crystal growth ,Chemical engineering ,Particle size ,Particle density ,computer ,computer.programming_language - Abstract
Based on the systematic studies of the growth temperature, deposition rate, and annealing effects, the control of Co nanoparticle density, size, and alignment is demonstrated to be feasible on a nanostructured template Al2O3∕NiAl(100). At 140–170K, a slow deposition rate (0.027ML∕min) promises both the linear alignment and the high particle density. 1.5 ML Co nanoparticle assembly sustains the density of ∼260∕104nm2 even after 800–1090K annealing. This study also indicates the possibilities of the controlled growth for nanoparticles of different materials.
- Published
- 2006
28. Pinned magnetic moments in exchange bias: Role of the antiferromagnetic bulk spin structure.
- Author
-
Yaqoob Khan, M., Chii-Bin Wu, and Kuch, Wolfgang
- Subjects
- *
MAGNETIC moments , *ANTIFERROMAGNETIC materials , *MAGNETIC properties , *MAGNETIC resonance , *KERR magneto-optical effect , *MAGNETIC materials - Abstract
Magneto-optical Kerr effect measurements of epitaxial AFM/FM bilayers and FM/AFM/FM trilayers on Cu3Au(001), where "AFM" stands for a Ni25Mn75 antiferromagnetic layer, and "FM" for ferromagnetic layers that are either Ni or Ni/Co with out-of-plane or in-plane easy axis of magnetization, show that trilayers with collinear magnetization directions of both FM layers exhibit always a much lower exchange bias field Heb at a fixed temperature compared to bilayers of the same Ni25Mn75 thickness. At the same time, the blocking temperature for exchange bias Tb is strongly reduced. In trilayers with orthogonal easy axes of the two FM layers (in-plane and out-of-plane), in contrast, both Heb and Tb are nearly identical to that of the corresponding bilayers. Such a behavior can be explained by pinned magnetic moments inside the bulk of the AFM layer that coexist independently for orthogonal spin directions, but have to be equally shared between both interfaces in the case of collinear spin directions. This result thus also confirms a 3Q-like noncollinear spin structure of Ni25Mn75. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
29. Concentration- and thickness-dependent magnetic properties of NixMn100-x in epitaxially grown NixMn100-x/Ni/(Co/)Cu3Au(001).
- Author
-
Khan, M. Yaqoob, Chii-Bin Wu, Kreft, Stefanie K., and Kuch, Wolfgang
- Published
- 2013
- Full Text
- View/download PDF
30. Enhanced photoluminescence of InGaAs/AlGaAs quantum well with tungsten disulfide quantum dots.
- Author
-
Wilson Yeung-Sy Su, Svette Reina Merden S Santiago, Chia-Cheng Chiang Hsieh, Chii-Bin Wu, Jyh-Shyang Wang, Kuan-Cheng Chiu, Ji-Lin Shen, Chih-Yang Huang, and Cheng-Ying Chen
- Subjects
PHOTOLUMINESCENCE ,TUNGSTEN ,OPTOELECTRONIC devices ,PULSED lasers ,LASER ablation ,QUANTUM dots ,QUANTUM wells - Abstract
The pristine and diethylenetriamine (DETA)-doped tungsten disulfide quantum dots (WS
2 QDs) with an average lateral size of about 5 nm have been synthesized using pulsed laser ablation (PLA). Introduction of the synthesized WS2 QDs on the InGaAs/AlGaAs quantum wells (QWs) can improve the photoluminescence (PL) of the InGaAs/AlGaAs QW as high as 6 fold. On the basis of the time-resolved PL and Kelvin probe measurements, the PL enhancement is attributed to the carrier transfer from the pristine or DETA-doped WS2 QDs to the InGaAs/AlGaAs QW. A heterostructure band diagram is proposed for explaining the carrier transfer, which increases the hole densities in the QW and enhances its PL intensity. This study is expected to be beneficial for the development of the InGaAs-based optoelectronic devices. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
31. Controlled growth of Co nanoparticle assembly on nanostructured template Al2O3/NiAl(100).
- Author
-
Wen-Chin Lin, Shen-Shing Wong, Po-Chun Huang, Chii-Bin Wu, Bin-Rui Xu, Cheng-Tien Chiang, Hong-Yu Yen, and Minn-Tsong Lin
- Subjects
NANOPARTICLES ,SCANNING tunneling microscopy ,NANOTUBES ,NANOWIRES ,ANNEALING of metals ,PARTICLE size determination ,PARTICLE size distribution - Abstract
Based on the systematic studies of the growth temperature, deposition rate, and annealing effects, the control of Co nanoparticle density, size, and alignment is demonstrated to be feasible on a nanostructured template Al
2 O3 /NiAl(100). At 140–170 K, a slow deposition rate (0.027 ML/min) promises both the linear alignment and the high particle density. 1.5 ML Co nanoparticle assembly sustains the density of ∼260/104 nm2 even after 800–1090 K annealing. This study also indicates the possibilities of the controlled growth for nanoparticles of different materials. [ABSTRACT FROM AUTHOR]- Published
- 2006
- Full Text
- View/download PDF
32. Nanopatterning of magnetic domains: Fe coverage of self-assembled alumina nanostructure.
- Author
-
Chii-Bin Wu, Bo-Yao Wang, Wen-Chin Lin, Zheng Gai, and Minn-Tsong Lin
- Abstract
Nanosized ultrathin magnetic films were prepared by controlling the deposition of Fe onto an oxidized NiAl(001) surface with an alumina nanostructure on it. Because the ultrathin ferromagnetic Fe films on the bare NiAl(001) surface are separated by paramagnetic Fe nanoparticles on the alumina stripes, as determined by scanning electron microscopy with spin analysis, they form rectangular domains with sizes ranging from tens of nanometer to larger than a micrometer. Magnetic domain patterning can thus be achieved by controlling the Fe coverage and nanostructured template. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
33. Layered antiferromagnetic spin structures of expanded face-centered-tetragonal Mn(001) as an origin of exchange bias coupling to the magnetic Co layer.
- Author
-
Pin-Jui Hsu, Chun-I Lu, Yu-Hsun Chu, Bo-Yao Wang, Chii-Bin Wu, Lun-Jia Chen, Sheng-Syun Wong, and Minn-Tsong Lin
- Subjects
- *
ANTIFERROMAGNETISM , *COPPER alloys , *MAGNETIC properties of metals , *MAGNETIC coupling , *SCANNING tunneling microscopy , *MICROMAGNETICS , *INTERFACES (Physical sciences) - Abstract
Spin structures of an exchange-coupled-bilayer system of expanded-face-centered-tetragonal (e-fct) Mn(001) ultrathin films grown on Co/Cu(001) were resolved by means of spin-polarized scanning-tunneling microscopy. With an in-plane spin-sensitive probe, a layered antiferromagnetic-spin ordering of Mn overlayers was evidenced directly. In addition, the spin frustration across the same Mn layer creating a narrow domain wall down to nanometer scale was also observed along the buried step of Co underlayers. According to the micromagnetic simulation, the step-induced domain-wall width is in agreement with the experimental results. Such in-plane layered antiferromagnetic-spin structures of e-fct Mn(001) provide uncompensated spins at the interface with Co underlayers and elucidate the mechanism of the corresponding exchange-bias field observed in the previous studies. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
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