Browsing by Author "Wu, W. W."

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A solid-state cation exchange reaction to form multiple metal oxide heterostructure nanowires
(2016)
Chen, Y. H.
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Huang, C. W.
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Yeh, P. H.
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Chen, J. Y.
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Lin, T. Y.
Metal oxide nanostructures have been investigated extensively due to their wide range of physical properties; zinc oxide is one of the most promising materials. It exhibits fascinating functional properties and various types of morphologies. In particular, ZnO heterostructures have attracted great attention because their performance can be modified and further improved by the addition of other materials. In this study, we successfully transformed ZnO nanowires (NWs) into multiple ZnO/Al2O3 heterostructure NWs via a solid-state cation exchange reaction. The experiment was carried out in situ via an ultrahigh vacuum transmission electron microscope (UHV-TEM), which was equipped with a video recorder. Moreover, we analyzed the structure and composition of the heterostructure NWs by Cs-corrected STEM equipped with EDS. Based on these experimental results, we inferred a cation exchange reaction ion path model. Additionally, we investigated the defects that appeared after the cation reaction, which resulted from the remaining zinc ions. These multiple heterostructure ZnO/Al2O3 NWs exhibited excellent UV sensing sensitivity and efficiency.
Controlled large strain of Ni silicide/Si/Ni silicide nanowire heterostructures and their electron transport properties
(2010-11-15)
Wu, W. W.
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Lu, K. C.
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Chen, K. N.
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Yeh, P. H.
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Wang, C. W.
Unusually large and compressively strained Si in nanoheterostructures of Ni silicide/Si/Ni silicide, in which the strain of the Si region can be achieved up to 10%, has been produced with point contact reactions between Si and Ni nanowires in an ultrahigh vacuum transmission electron microscope. The growth rate and relationships between the strain and the spacing of the Si region have been measured. Based on the rate and relationships, we can control the Si dimension and, in turn, the strain of remaining Si can be tuned with appropriate spacing. Since one-dimensional nanoheterostructures may have potential applications in nanoelectronic devices, the existent strain will further affect carrier mobility and piezoresistance coefficients in the Si region. Electrical measurements on the nanodevices from such nanoheterostructures show that the current output closely correlates with the Si channel length and compressive strain. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3515421]
Enhanced growth of low-resistivity titanium silicides on epitaxial Si(0.7)Ge(0.3) on (001)Si with a sacrificial amorphous Si interlayer
(2010-10-01)
Wu, W. W.
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Wang, C. W.
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Chen, K. N.
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Cheng, S. L.
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Lee, S. W.
Enhanced growth of low-resistivity self-aligned titanium silicides on epitaxial Si(0.7)Ge(0.3) with a sacrificial amorphous Si (a-Si) interlayer has been achieved. The a-Si layer with appropriate thickness was found to prevent Ge segregation, decrease the growth temperature, as well as maintain the interface flatness and morphological stability in forming low-resistivity C54-TiSi(2) on Si(0.7)Ge(0.3) grown by molecular beam epitaxy. The process promises to be applicable to the fabrication of high-speed Si-Ge devices. (C) 2010 Published by Elsevier B.V.
Enhanced growth of low-resistivity titanium silicides on epitaxial Si0.7Ge0.3 on (001)Si with a sacrificial amorphous Si interlayer
(2010-10-01)
Wu, W. W.
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Wang, C. W.
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Chen, K. N.
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Cheng, S. L.
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Lee, S. W.
Enhanced growth of low-resistivity self-aligned titanium silicides on epitaxial Si0.7Ge0.3 with a sacrificial amorphous Si (a-Si) interlayer has been achieved. The a-Si layer with appropriate thickness was found to prevent Ge segregation, decrease the growth temperature, as well as maintain the interface flatness and morphological stability in forming low-resistivity C54-TiSi2 on Si0.7Ge0.3 grown by molecular beam epitaxy. The process promises to be applicable to the fabrication of high-speed Si-Ge devices. (C) 2010 Published by Elsevier B.V.
Fabrication of Nano-Scale Cu Bond Pads with Seal Design in 3D Integration Applications
(2011-04-01)
Chen, K. N.
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Tsang, C. K.
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Wu, W. W.
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Lee, S. H.
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Lu, J. Q.
A method to fabricate nano-scale Cu bond pads for improving bonding quality in 3D integration applications is reported. The effect of Cu bonding quality on inter-level via structural reliability for 3D integration applications is investigated. We developed a Cu nano-scale-height bond pad structure and fabrication process for improved bonding quality by recessing oxides using a combination of SiO(2) CMP process and dilute HF wet etching. In addition, in order to achieve improved wafer-level bonding, we introduced a seal design concept that prevents corrosion and provides extra mechanical support. Demonstrations of these concepts and processes provide the feasibility of reliable nano-scale 3D integration applications.
Formation of In(2)O(3) nanorings on Si substrates
(2010-11-01)
Hsin, C. L.
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Yu, S. Y.
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Huang, C. W.
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Wu, W. W.
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材料科學與工程學系
A new approach to form the In(2)O(3) nanorings (NRs) has been proven by tailoring the difference between property of metal and metal oxide. The formation process of the In(2)O(3) NRs is proposed to be resulted form a subtle competition between the oxidation and evaporation of indium at the rim and center, respectively. Patterned In(2)O(3) NRs have been grown on (001) Si substrates in combination with nanosphere lithography. The size and morphology of the NRs can be controlled by the size of polystyrene nanospheres and the thickness of indium layer. The optical property measurements showed that the In(2)O(3) NRs are sensitive in absorption and emission of light between 600 and 622 nm in wavelength. The patterned In(2)O(3) NRs on silicon are advantageous for fabricating optical-response photonic devices at the desired locations and direct integration to the silicon-based photonic devices with current processing technology. (c) 2010 American Institute of Physics. [doi:10.1063/1.3511539]
Formation of In2O3 nanorings on Si substrates
(2010-11-01)
Hsin, C. L.
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Yu, S. Y.
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Huang, C. W.
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Wu, W. W.
;
材料科學與工程學系
A new approach to form the In2O3 nanorings (NRs) has been proven by tailoring the difference between property of metal and metal oxide. The formation process of the In2O3 NRs is proposed to be resulted form a subtle competition between the oxidation and evaporation of indium at the rim and center, respectively. Patterned In2O3 NRs have been grown on (001) Si substrates in combination with nanosphere lithography. The size and morphology of the NRs can be controlled by the size of polystyrene nanospheres and the thickness of indium layer. The optical property measurements showed that the In2O3 NRs are sensitive in absorption and emission of light between 600 and 622 nm in wavelength. The patterned In2O3 NRs on silicon are advantageous for fabricating optical-response photonic devices at the desired locations and direct integration to the silicon-based photonic devices with current processing technology. (c) 2010 American Institute of Physics. [doi:10.1063/1.3511539]
Growth of Multiple Metal/Semiconductor Nanoheterostructures through Point and Line Contact Reactions
(2010-10-01)
Wu, W. W.
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Lu, K. C.
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Wang, C. W.
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Hsieh, H. Y.
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Chen, S. Y.
Forming functional circuit components in future nanotechnology requires systematic studies of solid-state chemical reactions in the nanoscale Here, we report efficient and unique methods, point and line contact reactions on Si nanowtres, fabricating high quality and quantity of multiple nanoheterostructures of NiSi/Si and investigation of NiSi formation in nanoscale By using the point contact reaction between several Ni nanodots and a Si nanowire carried out in situ in an ultrahigh vacuum transmission electron microscopy, multiple sections of single-crystal NISI and Si with very sharp interfaces were produced in a Si nanowire Owing to the supply limited point contact reaction, we propose that the nucleation and growth of the sugar cane-type NISI grains start at the middle of the point contacts between two Ni nanodots and a Si nanowire The reaction happens by the dissolution of Ni into the Si nanowire at the point contacts and by interstitial diffusion of Ni acorns within a Si nanowire. The growth of NISI stops as the amount of Ni in the Ni nanodots is consumed Additionally, without lithography, utilizing the line contact reaction between PS nanosphere-mediated Ni nanopatterns and a nanowire of Si. we have fabricated periodic multi-NiSi/Si/NiSi heterostructure nanonowires that may enhance the development of circuit elements in nanoscale electronic devices Unlike the point contact reaction, suicide growth starts at the contact area in the line contact reaction, the different silicide formation modes resulting from point and line contact reactions are compared and analyzed A mechanism on the basis of flux divergence is proposed for controlling the growth of the nanomultiheterostructures
Growth of Multiple Metal/Semiconductor Nanoheterostructures through Point and Line Contact Reactions
(2010-10-01)
Wu, W. W.
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Lu, K. C.
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Wang, C. W.
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Hsieh, H. Y.
;
Chen, S. Y.
Forming functional circuit components in future nanotechnology requires systematic studies of solid-state chemical reactions in the nanoscale Here, we report efficient and unique methods, point and line contact reactions on Si nanowtres, fabricating high quality and quantity of multiple nanoheterostructures of NiSi/Si and investigation of NiSi formation in nanoscale By using the point contact reaction between several Ni nanodots and a Si nanowire carried out in situ in an ultrahigh vacuum transmission electron microscopy, multiple sections of single-crystal NISI and Si with very sharp interfaces were produced in a Si nanowire Owing to the supply limited point contact reaction, we propose that the nucleation and growth of the sugar cane-type NISI grains start at the middle of the point contacts between two Ni nanodots and a Si nanowire The reaction happens by the dissolution of Ni into the Si nanowire at the point contacts and by interstitial diffusion of Ni acorns within a Si nanowire. The growth of NISI stops as the amount of Ni in the Ni nanodots is consumed Additionally, without lithography, utilizing the line contact reaction between PS nanosphere-mediated Ni nanopatterns and a nanowire of Si. we have fabricated periodic multi-NiSi/Si/NiSi heterostructure nanonowires that may enhance the development of circuit elements in nanoscale electronic devices Unlike the point contact reaction, suicide growth starts at the contact area in the line contact reaction, the different silicide formation modes resulting from point and line contact reactions are compared and analyzed A mechanism on the basis of flux divergence is proposed for controlling the growth of the nanomultiheterostructures
In situ TEM investigation of dynamical changes of nanostructures
(2010-11-22)
Chen, L. J.
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Wu, W. W.
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材料科學與工程學系
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Department of Materials Science and Engineering
In situ investigation of the temperature induced phase transformation, structural and chemical evolution of nanocrystals is important for understanding the structure and stability of nanomaterials. Transmission electron microscopy (TEM), one of the most powerful tools for characterizing nanostructured materials, is essential for the development of nanotechnology. In situ TEM is a technique that allows a direct observation of dynamic properties in nanoscale. Recent development of ultra-high vacuum TEM (UHV-TEM) further enables the investigation on atomic-scale materials systems in a clean environment. The appropriate utilization of the UHV-TEM will be beneficial in studying the fundamental mechanisms of dynamic reactions, formation of transient phase, solid-state amorphization, epitaxial growth, growth kinetics and evolution of defects. In this paper, we present the most recent progress in observing dynamic processes in nanoscale by in situ UHV-TEM. (C) 2010 Elsevier B.V. All rights reserved.
In situ TEM investigation of dynamical changes of nanostructures
(2010-11-22)
Chen, L. J.
;
Wu, W. W.
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In situ investigation of the temperature induced phase transformation, structural and chemical evolution of nanocrystals is important for understanding the structure and stability of nanomaterials. Transmission electron microscopy (TEM), one of the most powerful tools for characterizing nanostructured materials, is essential for the development of nanotechnology. In situ TEM is a technique that allows a direct observation of dynamic properties in nanoscale. Recent development of ultra-high vacuum TEM (UHV-TEM) further enables the investigation on atomic-scale materials systems in a clean environment. The appropriate utilization of the UHV-TEM will be beneficial in studying the fundamental mechanisms of dynamic reactions, formation of transient phase, solid-state amorphization, epitaxial growth, growth kinetics and evolution of defects. In this paper, we present the most recent progress in observing dynamic processes in nanoscale by in situ UHV-TEM. (C) 2010 Elsevier B.V. All rights reserved.
In Situ Ultrahigh Vacuum Transmission Electron Microscope Investigations of Nanostructures
(2009-07-01)
Chen, L. J.
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Wu, W. W.
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材料科學與工程學系
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Department of Materials Science and Engineering
In-situ TEM Study of Electromigration in Cu lines
(2009)
Liao, C. N.
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Chen, K. C.
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Wu, W. W.
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Chen, L. J.
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Tu, K. N.
The density of electric current passing through interconnecting wires in integrated circuits (IC) is increasing with continuous miniaturization of IC. Under a high operating temperature and large electric current density, some voids and hillocks may form in the interconnecting wires due to electromigration (EM), leading to device failures eventually. In this study atomic-scale EM in unpassivated copper lines has been investigated in ultrahigh vacuum by in situ transmission electron microscopy (TEM). The EM-induced atomic surface diffusion was found to be crystal-orientation dependent and occurred preferentially on the {111} planes along < 110 > directions. The high-resolution TEM images and the electron diffraction patterns of a (111)-oriented Cu grain in the Cu line revealed an EM-induced step structure at surface. Moreover, the triple point where a twin boundary meets a grain boundary was found to slow down atomic EM at grain boundaries because of the incubation time of nucleation of a new step at the triple point. The long incubation time slows down the overall rate of atomic transport. The results suggest that the EM reliability of Cu interconnects may be enhanced by forming a high density of nanometer scaled twins in the coarse-grain Cu wires.
In-situ Ultrahigh Vacuum Transmission Electron Microscope Investigations of Nanostructures
(2010)
Chen, L. J.
;
Wu, W. W.
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Low-dimensional nanostructures, such as nanodots, nanowires and nanotubes, are especially attractive candidates for developing a bottom-up paradigm for nanotechnology-enabled architectures. In situ ultrahigh vacuum transmission electron microscope (UHV-TEM) is a powerful tool to investigate the dynamic changes of nanostructures. By observing growth and phase transitions in situ, understanding of their mechanisms can be used to model relevant processes. Recent development of UHV-TEM further enables the investigation on atomic-scale materials systems in a clean environment. With the precise knowledge of the changes occurred on an atomic level, accurate control of the growth process can be achieved [1]. The appropriate utilization of the UHV-TEM will be beneficial in studying the fundamental mechanisms of dynamic reactions, formation of transient phase, solid-state amorphization, epitaxial growth, growth kinetics and evolution of defects. The dynamical changes occurred on the nano scale are often unexpected, which also underscores the importance of the approach. In this presentation, we will highlight several examples to demonstrate the unique capability of in situ TEM to study the dynamical changes. The examples include growth of high-density titanium silicide nanowires in a single direction on a silicon surface [2], controlled growth of atomic-scale Si layer with huge strain in the nano-heterostructure NiSi/Si/NiSi through point contact reaction between nano-wires of Si and Ni and reactive epitaxial growth [3], observation of repeating events of nucleation in epitaxial growth of nano CoSi2 in nanowires of Si [4] and observations of electromigration in copper lines at room temperature [5].
Investigation and Effects of Wafer Bow in 3D Integration Bonding Schemes
(2010-12-01)
Chen, K. N.
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Zhu, Y.
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Wu, W. W.
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Reif, R.
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材料科學與工程學系
This paper investigates and reviews the effects of wafer bow in three- dimensional (3D) integration bonding schemes, including copper wafer bonding and oxide fusion wafer bonding with silicon on insulator (SOI)-based layer transfer technology. Wafer bow criteria for good bonding quality and fabrication techniques to minimize wafer bow are introduced for 3D integration technology and applications.
Ni silicide formation on epitaxial Si(1-y)C(y)/(001) layers
(2010-10-01)
Lee, S. W.
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Huang, S. H.
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Cheng, S. L.
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Chen, P. S.
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Wu, W. W.
The formation of Ni silicides on Si(1 - y)C(y) (y=0.01 and 0.018) epilayers grown on Si(001) has been investigated. The presence of C atoms was found to significantly retard the growth kinetics of NiSi and enhances the thermal stability of thin NiSi films. For Ni(11 nm)/Si(0.982)C(0.018) samples, the process window of NiSi was shifted and extended to 450-700 degrees C. Moreover, there was an additional strain introduced into the Si(1 - y)C(y) epilayers during Ni silicidation. This work shows the potential of Ni silicidation on Si(1y)C(y) for device applications. (C) 2010 Elsevier B.V. All rights reserved.
Ni silicide formation on epitaxial Si1-yCy/(001) layers
(2010-10-01)
Lee, S. W.
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Huang, S. H.
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Cheng, S. L.
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Chen, P. S.
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Wu, W. W.
The formation of Ni silicides on Si1 - yCy (y=0.01 and 0.018) epilayers grown on Si(001) has been investigated. The presence of C atoms was found to significantly retard the growth kinetics of NiSi and enhances the thermal stability of thin NiSi films. For Ni(11 nm)/Si0.982C0.018 samples, the process window of NiSi was shifted and extended to 450-700 degrees C. Moreover, there was an additional strain introduced into the Si1 - yCy epilayers during Ni silicidation. This work shows the potential of Ni silicidation on Si1yCy for device applications. (C) 2010 Elsevier B.V. All rights reserved.