Browsing by Author "Wang, C. W."

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Antiferroelectric antiferromagnetic type-I multiferroic Cu9O2(SeO3)(4)Cl-6
(2019-12-11)
Wu, H. C.
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Denisova, K. N.
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Menzel, D.
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Kakarla, D. Chandrasekhar
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Maximova, O. V.
We report that Cu9O2(SeO3)(4)Cl-6 is a new multiferroic compound. Comprehensive studies of this compound have been carried out on single crystals as well as polycrystalline samples. Magnetic susceptibility chi and specific heat C with H parallel to c axis both reveal an anomaly at T-N = 37 K associated with the long-range antiferromagnetic order. However, no signature of this phase transition is seen with the H parallel to b axis, providing evidence of the anisotropic nature of its magnetic properties. The results of chi measurements are consistent with the temperature evolution of the intensity of magnetic reflections from the neutron diffraction experiments. The magnetic structure derived from neutron scattering measurements shows that half of the Cu(5) ions carry no moments. Furthermore, an anomaly in the dielectric constant near T-N and observable magnetoelectric coupling below T-N are found. At high temperatures, a dielectric peak at T-E = 267 K is identified with no measurable spontaneous polarization below T-E, thereby suggesting an antiferroelectric order. A steplike anomaly seen in chi(T) at T-E hints the weak spin-lattice coupling. Concomitantly, high-resolution temperature-dependent synchrotron x-ray diffraction experiments elucidate a local structural distortion at T-E.
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]
Correlation between SET-State Current Level and Read Disturb Failure Time in a Resistive Switching Memory
(2018-01-01)
Su, P. C.
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Jiang, C. M.
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Wang, C. W.
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Wang, Tahui
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電子工程學系及電子研究所
The relationship between SET-state current level and read-disturb failure time in a tungsten oxide RRAM is characterized and modeled. Our result shows that read voltage induced reduction of oxygen vacancy density in tungsten oxide follows a power law dependence on cumulative read-disturb time. The power factor is independent of SET-state current level. Read disturb failure time is considerably improved by several orders of magnitude as SET-state current level increases a few times. An analytical model to correlate SET-state current level and read disturb failure time is proposed. Since SET-state current level is related to a cross-section of a conductive filament in an oxide, our model is developed based on a relationship between oxide area and critical oxide trap (oxygen vacancy) density from an oxide breakdown model. The validity of the proposed model is supported by experiment results.
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.
;
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.
;
Wang, C. W.
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Chen, K. N.
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Cheng, S. L.
;
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.
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.
;
Lu, K. C.
;
Wang, C. W.
;
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
National Project on 45 to 32 nm Metal Oxide Semiconductor Field Effect Transistors for Next Century IC Fabrications
(2008)
Hwang, Huey-liang
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Wang, C. W.
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Chang, K. H.
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Tsai, C. H.
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Leou, K. C.
It is well known that the Taiwan Semiconductor industries play the very key roles for the worldwide IC foundry, and the advanced research of nanoelectronics is the lifeline for its long term developments. Professor Huey-liang Hwang effectively integrated the most outstanding research team and resource in Taiwan on the National Project on Nanometer CMOS Transistors for the 21 century, which is sponsored by the Ministry of Economic Affairs of ROC. A dozen of Professors from NTHU( National Tsing Hua University) with expertise at the novel materials and analysis and NCTU( National Chiao Tung University) with expertise at devices and reliability are devoted to the studies and are in collaboration with the world-wide-known company such as TSMC, and breakthrough of the key technologies of 45-32 nm technologies are achieved. The objective of this project is focused on the development of advanced metal gate/high-k MOSFET for 45 nm node generation and beyond, the efforts include the world first successful suppression the oxide/Si interfacial layer formation by using a bi-layer composite of HfO2 3.2 nm (ALD)/HfO2 1.5 nm (MBE), the results show a dielectric constant of 16 and an EOT of 1.15 nm, a Dit was estimated to be 4.6x10(11)cm(-2)eV(-1) with the leakage at Vfb-1V being 8.5x10(-6) A/cm(2). Also, the thermal stability of HfO2, HfAlOx alloy and Al2O3/HfO2 stack, prepared by ALD were compared, the incorporation of Al in alloy form gave superior characteristics by retaining an amorphous structure up to 1000 C, which suppress the leakage current and retards growth of the interfacial layer giving the least increment of EOT and interface traps. Besides, by incorporating Al into TiO2 gave an EOT value of the Al2O3/TiAlOx/Al2O3 film down to 0.8 nm. Furthermore, high selectivity was obtained via etching the HfAlO and silicon wafer with pattern using the ICP Plasma. In this project, YbSi metal gate for n-MOSFET and IrSi metal gate p-MOSFET were successfully fabricated for the HfAlON MESFET. The results showed the good effective workfunction of 4.15 and 4.9 eV and no degradation of gate dielectric current and mobility in the YbxSi/HfAlON and IrxSi/HfAlON FUSI-gates by reducing the metal diffusion at lower temperatures.
Observation of charge-transfer-driven antiferroelectricity in 3d-pyrochlore multiferroic Cu2OCl2
(2019-03-01)
Wu, H. C.
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Yuan, J. K.
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Chandrasekhar, K. D.
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Lee, C. H.
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Li, W. H.
Very recently, multiferroic behavior close to the boiling temperature of liquid nitrogen was reported in oxohalide-based Cu2OCl2. In this study, we have established yet another novel mechanism for the origin of charge ordering in multiferroic Cu2OCl2. The direct current (DC) magnetization, specific heat, and neutron diffraction measurements confirm the antiferromagnetic (AFM) ordering (T-N) of Cu2OCl2 near 70 K. The collinear AFM spin structure in Cu(2)OCl(2)was obtained from neutron powder diffraction experiments based on the fitting to the combination of two irreducible representations-Gamma(1)circle plus Gamma(2). Electrical properties, such as dielectric constant, pyroelectric current, and polarization-electric field hysteresis-loop measurements, together suggest a long-range antiferroelectric ordering near T-E approximate to 75 K. The charge transfer from Cl to O along the c-axis was found to induce antiferroelectricity near TE and is supported from ab initio calculations. This finding largely reduces the possibility of well-known Dzyaloshinskii -Moriya interaction in the observed multiferroic behaviors and provides insight into the various origins of high-T-c multiferroics. (C) 2018 Elsevier Ltd. All rights reserved.
The distribution of species and susceptibility of amphotericin B and fluconazole of yeast pathogens isolated from sterile sites in Taiwan
(2010-03-01)
Yang, Y. L.
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Cheng, M. F.
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Wang, C. W.
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Wang, A. H.
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Cheng, W. T.
To study the demographic changes of yeasts causing invasive infections in Taiwan, especially with respect to species distribution and antifungal susceptibility, we analyzed isolates obtained from four sterile sites of patients in 19 hospitals in 2002 (155 strains) and again from the same hospitals in 2006 (208 strains). Blood was the most common source of the yeasts, accounting for 73.8% of the total isolates, followed by ascites (21.5%), cerebrospinal fluid (3%), and synovia (1.7%). Candida albicans was the most frequently recovered species (50.1% of the total), followed by Candida tropicalis (20.7%), Candida glabrata (11.6%), Candida parapsilosis (8.5%), Cryptococcus neoformans (3.9%), Candida krusei (0.8%), and nine other species (4.3%). There were one (0.3%) and seven (1.9%) isolates with minimum inhibitory concentrations (MICs) of amphotericin B >= 2 mg/l after 24 h and 48 h incubation, respectively. In addition, there were 15 (4.3%) and 31 (8.6%) isolates with MICs of fluconazole >= 64 mg/l under the same conditions. The MIC(90) value of amphotericin B was 1 mg/l. The MIC(90) values of fluconazole were 4 mg/l after 24 h incubation and 32 mg/l after 48 h incubation. Interestingly, MICs for fluconazole >= 64 mg/l after 24 h were significantly higher for isolates obtained in 2006 than those in 2002 after 24 h (7.1% vs. 0.7%, p = 0.009) and 48 h (13.5% vs. 2%, p = 0.0003) incubations. The demographic difference between these two surveys is mainly due to one species, C. tropicalis.