Browsing by Author "Chen, IW"

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Comparative role of metal-organic decomposition-derived [100] and [111] in electrical properties of Pb(Zr,Ti)O-3 thin films
(1997-07-01)
Chen, SY
;
Chen, IW
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The effect of composition (phase), texture, microstructure and thickness on electrical properties of Pb(Zr1-zTiz)O-3 (PZT) films have been evaluated. Zr-rich PZT films with [111] texture have a higher remanent polarization and dielectric constant, but a lower coercive field as compared with PZT[100] films. Ti-rich PZT films with [100] texture have a higher dielectric constant, but a lower remanent polarization and coercive field as compared with PZT[111] films. Near the morphotropic phase boundary (MPB) composition, films with a mixed texture of [111] and [100] have a higher dielectric constant than PZT[100] and PZT[111] films even though the values of remanent polarization and coercive field of the mixed textured films are in between those of the other two films. Both remanent and saturation polarization are independent of film thickness, whereas dielectric constant decreases but coercive field increases at very small thickness.
Comparative role of metal-organic decomposition-derived [100] and [111] in electrical properties of Pb(Zr,Ti)O-3 thin films
(1997-07-01)
Chen, SY
;
Chen, IW
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The effect of composition (phase), texture, microstructure and thickness on electrical properties of Pb(Zr1-zTiz)O-3 (PZT) films have been evaluated. Zr-rich PZT films with [111] texture have a higher remanent polarization and dielectric constant, but a lower coercive field as compared with PZT[100] films. Ti-rich PZT films with [100] texture have a higher dielectric constant, but a lower remanent polarization and coercive field as compared with PZT[111] films. Near the morphotropic phase boundary (MPB) composition, films with a mixed texture of [111] and [100] have a higher dielectric constant than PZT[100] and PZT[111] films even though the values of remanent polarization and coercive field of the mixed textured films are in between those of the other two films. Both remanent and saturation polarization are independent of film thickness, whereas dielectric constant decreases but coercive field increases at very small thickness.
Texture development, microstructure evolution, and crystallization of chemically derived PZT thin films
(1998-01-01)
Chen, SY
;
Chen, IW
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Two solution-based methods, metallo-organic decomposition and sol-gel processes, were used to study the effects of precursor solution type on the microstructure evolution and texture development of oriented PZT films. Microstructure development and perovskite content are strongly dependent on the heating rate. Fast heating rate forms a dense fine-grained microstructure with (111) orientation. Intermediate-temperature pyrolysis followed by a fast heating rate forms clustered or island structures of submicrometer grains with (100) orientation. Intermediate-temperature pyrolysis followed by a very slow heating rate forms larger spherical rosettes with random orientations. Pt5-7Pb is a (111) textured transient intermetallic phase that nucleates PZT(111) texture. PbO is a (001) textured layer compound that nucleates PZT(100) texture. The texture selection of PZT films is independent of precursor systems but sensitive to the film thickness especially when sol-gel precursors and oxidizing atmosphere are used. Correlation and comparison of oriented sol-gel and MOD PZT films with electrical properties are also made.
Texture development, microstructure evolution, and crystallization of chemically derived PZT thin films
(1998-01-01)
Chen, SY
;
Chen, IW
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Two solution-based methods, metallo-organic decomposition and sol-gel processes, were used to study the effects of precursor solution type on the microstructure evolution and texture development of oriented PZT films. Microstructure development and perovskite content are strongly dependent on the heating rate. Fast heating rate forms a dense fine-grained microstructure with (111) orientation. Intermediate-temperature pyrolysis followed by a fast heating rate forms clustered or island structures of submicrometer grains with (100) orientation. Intermediate-temperature pyrolysis followed by a very slow heating rate forms larger spherical rosettes with random orientations. Pt5-7Pb is a (111) textured transient intermetallic phase that nucleates PZT(111) texture. PbO is a (001) textured layer compound that nucleates PZT(100) texture. The texture selection of PZT films is independent of precursor systems but sensitive to the film thickness especially when sol-gel precursors and oxidizing atmosphere are used. Correlation and comparison of oriented sol-gel and MOD PZT films with electrical properties are also made.
Tunnel minimization and relay for managing virtual private networks
(2004)
Chen, IW
;
Lin, YD
;
Lin, YN
;
資訊工程學系
;
Department of Computer Science
A virtual private network (VPN) is a private data network that carries traffic between remote sites. One of the most popular VPN applications is the "Intranet/Extranet VPN", which establishes network layer connections between remote intranet sites, using various tunneling protocols, to create an IP overlay network. IPSec, which is very prevalent in industry, is one of these tunneling protocols that not only provide encapsulation/decapsulation but encryption/decryption and hashing. However, an IPSec tunnel often fails to be established due to the management complexity. This work proposes the new concept of authority to alleviate the management overhead by reducing the number of tunnels. The problem of tunnel minimization is first formalized under three conditions-no constraint, a Tunnel Path Length constraint and a Tunnel Relay Degree constraint, and then solved using graphical models and the Zero-One Integer Programming algorithm. The effect of tunnel minimization is also investigated, and at most 90% of the tunnels are found to be reducible in a general enterprise VPN.