Sham-tsong Shiue - Academia.edu (original) (raw)

Papers by Sham-tsong Shiue

Journal of Materials Research, Aug 1, 1993

Based on the results of Shiue and Lee [J. Appl. Phys. 70, 2947 (1991)], the effect of plastic zon... more Based on the results of Shiue and Lee [J. Appl. Phys. 70, 2947 (1991)], the effect of plastic zone and grain boundary on the dislocation emission criterion was investigated. The emission criterion is based on the concept of spontaneous emission. The critical stress intensity factor for dislocation emission increases with the increasing size of dislocation-free zone and the number of piled-up dislocations in the plastic zone, but decreases with increasing grain size. The ductile versus brittle behavior of material was determined by the competition of critical stress intensity factors for dislocation emission and crack propagation. A material with larger grain size is easier to emit dislocation and allows more dislocations to be piled up, so that it behaves more ductile.

Philosophical Magazine A, Jun 1, 1993

Abstract Dislocations piled up between a finite crack tip and a grain boundary ledge with a dislo... more Abstract Dislocations piled up between a finite crack tip and a grain boundary ledge with a dislocation-free zone are investigated by a continuous dislocation modelling method. The dislocation distribution function to simulate the crack and plastic zone is analytically derived. A closed form for the number of dislocations in the plastic zone is analytically derived. A closed form for the number of dislocations in the plastic zone and stress field is obtained. From the stress field, the stress intensity factor K m and stress concentration at the grain boundary are obtained. When there is no dislocation-free zone in front of crack tip, the stress intensity factor K m is zero, no matter whether the grain boundary exists or not. The effect of the grain boundary ledge on the fracture toughness and the effect of the crack on the strength of the grain boundary, such as described by the Hall-Petch equation, are discussed. Finally, our results can reduce to several special cases, and these are discussed.

International Journal of Fracture, 1995

The elastic interaction between an edge dislocation and two collinear internal cracks of differen... more The elastic interaction between an edge dislocation and two collinear internal cracks of different length has been investigated. The effect of the distance between two collinear cracks on the crack shielding and image force on the edge dislocation were examined. The effect of the length of the right-hand-side crack on the shielding of the left-hand-side crack and the image force

Applied Physics Letters, Mar 13, 2006

Electrical performance was found to be closely related to the variation of nanosized interface mo... more Electrical performance was found to be closely related to the variation of nanosized interface morphology in previous studies. This work investigated in detail the microstructural development of in-and anti-phase bonded interfaces for n-type ͑100͒ GaAs wafers treated at 500, 600, 700 and 850°C. The interfacial energy of anti-phase bonding is higher than that of in-phase bonding based on the first-principles calculations. The higher interface energy tends to stabilize the interfacial oxide layer. The continuous interfacial oxide layer observed below 700°C can deteriorate the electrical property due to its insulating property. However, the existence of nanoscaled oxide at anti-phase bonded interfaces can improve the electrical conductivity at 700°C. This is due to the suppression of the evaporation of As atom by the interfacial nanoscaled oxides based on the analysis of autocorrelation function and energy dispersive x-ray spectroscopy.

Materials Chemistry and Physics, Feb 1, 2004

The effect of polymeric coatings on the static fatigue of tightly jacketed double-coated optical ... more The effect of polymeric coatings on the static fatigue of tightly jacketed double-coated optical fibers is theoretically analyzed. A closed form solution of the tensile stress in the glass fiber is obtained from viscoelastic theory. The tensile stress in the glass fiber in the static fatigue test increases with time due to the viscoelastic behavior of the polymeric coatings, and this increase will accelerate the failure of the optical fiber. The long-term strength of optical fibers can be improved by increasing the axial rigidities and the relaxation times of the secondary coating and the tight jacket. Finally, a rule to prevent the overestimation of fiber's lifetimes in the static fatigue test is proposed.

Thin Solid Films, Apr 1, 2014

The properties of carbon films prepared by thermal chemical vapor deposition (thermal CVD) using ... more The properties of carbon films prepared by thermal chemical vapor deposition (thermal CVD) using camphor are investigated. As the deposition temperature increases from 1098 to 1198 K, the deposition rate follows the Arrhenius law with activation energy of 59.8 kJ/mol. The possible reaction paths and intermediate species of this thermal CVD process are also considered. The product gases CH 3 , CH 4 , and C 2 H 2 can be speculated as the main species for pyrolytic carbon deposition. The crystallinity and ordering degree of carbon films decrease with increasing the deposition temperature. Nevertheless, the sp 2 carbon sites increase with increasing the deposition temperature, and results in the decrease of electrical resistivity and the increase of water contact angle. When the camphor weight changes from 0.06 to 0.50 g, the CVD reaction is controlled by a process of half order. Moreover, as the camphor weight increases from 0.30 to 0.50 g, the surfaces of carbon films are partially covered with spherical particles, the water contact angle substantially increases. Finally, the results of this work are compared to those of using CH 4 and C 2 H 2 as the precursor gases.

Journal of Applied Physics, Sep 1, 2010

The viscoelastic behavior of commercial UV-cured polymeric coatings of optical fibers is evaluate... more The viscoelastic behavior of commercial UV-cured polymeric coatings of optical fibers is evaluated using dynamic mechanic analysis. The results indicate that relaxation of stresses and/or strains in these coatings occurs by creep deformation. The axial strain-induced viscoelastic stresses in optical fibers are derived from the exact viscoelastic behavior of the polymeric coatings. Compressive radial stress on the glass fiber produces microbending losses, and therefore, microbending losses in double-coated optical fibers that are caused by axial strain-induced creep deformation of polymeric coatings are investigated. These microbending losses can be minimized by suitably selecting the thickness and physical properties of the polymeric coatings, as follows. The radius, Poisson’s ratio, and strain ratio of the primary coating should be increased, but the Young’s modulus and relaxation time of the primary coating should be decreased. The radius, Young’s modulus, Poisson’s ratio, and strain ratio of the secondary coating should be decreased, but the relaxation time of the secondary coating should be increased. When the thickness and physical properties of the polymeric coating are chosen to minimize the microbending loss, the thickness and Young’s modulus of the secondary coatings should be large enough to withstand an external mechanical force.

ECS Journal of Solid State Science and Technology, 2013

The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To ... more The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5∼7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeO x (3 nm)/Fe(3 nm)/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeO x and Fe/FePt layers was decoupled. The moments in FeO x layer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500 ∘ C and 800 ∘ C for 3 minutes. When the FeO x (3 nm)/Fe(3 nm)/FePt trilayer was annealed at 500 ∘ C, the layers structure was changed to FeO x (6 nm)/FePt bilayer due to oxygen diffusion. The hard-magnetic FeO x (6 nm)/FePt film was coupled with single switching field. The FeO x /(disordered FePt) layer structure was observed with further annealing at 800 ∘ C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeO x layer, and hard-magnetic L1 0 FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L1 0 FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800 ∘ C.

Optical Engineering, Jun 1, 2002

The design of tightly jacketed double-coated optical fibers to minimize long-term hydrostatic-pre... more The design of tightly jacketed double-coated optical fibers to minimize long-term hydrostatic-pressure-induced microbending losses is investigated. Microbending loss in these fibers is dominated by compressive radial stress at the interface between the glass fiber and the primary coating, which is a function of the polymeric materials properties and their thicknesses. To minimize the long-term hydrostatic-pressure-induced microbending losses, one should decrease

Journal of Applied Physics, Sep 1, 2004

This study theoretically investigates the effect of temperature cycling on the static fatigue of ... more This study theoretically investigates the effect of temperature cycling on the static fatigue of double-coated optical fibers. The tensile force and temperature cycling induced tensile stresses on the glass fiber of double-coated optical fibers are determined using the viscoelastic theory. Optical fibers lifetime is dominated by the tensile stress on the glass fibers, which is a function of the material properties and thickness of the polymeric coating. To minimize these stresses on the glass fiber, the radius, Young’s modulus, and thermal expansion coefficient of the secondary coating should be reduced, while the relaxation time of the secondary coating should be increased. Additionally, based on strength consideration, the radius and Young’s modulus of the polymeric coating should be sufficiently thick or hard to support the external mechanical stresses. Meanwhile, based on the microbending-insensitivity consideration, the relaxation time of the primary coating should be reduced.

Journal of Lightwave Technology, 2003

The design of double-coated optical fibers to minimize long-term tensile-force-induced delaminati... more The design of double-coated optical fibers to minimize long-term tensile-force-induced delamination of polymeric coatings from glass fibers is investigated using viscoelastic theory. To prevent the delamination of polymeric coatings from glass fibers, the tensile-force-induced interfacial shear stress between the glass fiber and primary coating should be always smaller than its interfacial shear strength in the long term. The tensile-force-induced interfacial

Optical Engineering, Apr 1, 2008

Growth of conical particles in carbon films deposited on silica glass fibers prepared by thermal ... more Growth of conical particles in carbon films deposited on silica glass fibers prepared by thermal chemical vapor deposition is investigated. The results show that the size and number of conical particles on the silica glass fiber increase with the film thickness and deposition temperature, but this effect is reduced when the carbon films are deposited on silica glass plates. The growth of conical particles on the silica glass fiber is mainly due to the small cross-sectional area of the fibers. These conical particles are against the hermetic property of carbon-coated optical fibers. We propose a method to minimize conical particles in carbon films on silica glass fibers.

Optical Engineering, Mar 1, 2007

The effects of annealing on the properties of hermetically carbon-coated optical fibers are inves... more The effects of annealing on the properties of hermetically carbon-coated optical fibers are investigated. The hermetically carbon-coated optical fibers are prepared by the plasma enhanced chemical vapor deposition method using methane and hydrogen as the precursor gases. The annealing temperatures are selected at 100, 200, 300, 400, and 500°C, respectively. The thickness, optical band gap, and microstructure of carbon films are measured. Meanwhile, the water-repellency and low-temperature surface morphology of carbon-coated optical fibers are evaluated. The results indicate that the thickness and defect content of the carbon films decrease with increasing the annealing temperature, while the degree of structure order and the amount of microcrystalline graphite in the carbon films increase. When the annealing temperature is over 300°C, the carbon films acquire enough thermal energy to cause a great amount of hydrogen and hydrocarbon to be released, and the carbon films transform to the graphitelike structure. Additionally, based on the evaluation of water-repellency and low temperature–induced break or delamination of carbon films, it is found that the carbon film annealed at 300°C is the best one for use as the hermetic optical fiber coating.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Jun 1, 1989

The elastic interaction between a screw dislocation and a welded surface crack in a thin plate of... more The elastic interaction between a screw dislocation and a welded surface crack in a thin plate of composite material has been analysed using the conformal mapping technique. The effect of size on fracture is pronounced when the ratio of thickness to crack length is less than 10. However, when it exceeds 10, the problem can be simply treated as that of a semi-infinite composite material Whether dislocation emission occurs at the tip also depends on the size of the specimen and the shear modulus ratio. The dislocation can be emitted more easily from the crack tip into the soft phase than into the hard one. The emitted angle of dislocation for minimal critical stress intensity factor increases with the shear modulus ratio. In addition, the results can be applied to several special cases. Finally, when the boundary value is not zero, such as in an applied stress, the mapping function must be selected carefully.

Thin Solid Films, Aug 1, 2005

The effect of the coating thickness and roughness on the mechanical strength and thermally induce... more The effect of the coating thickness and roughness on the mechanical strength and thermally induced stress voids in nickel-coated optical fibers is theoretically and experimentally investigated. Seven samples of nickel-coated optical fibers with identical fiber length but different coating thickness are prepared using electroless plating method. The thickness of the nickel coating is controlled by the plating time, with the thicknesses being 35, 65, 119, 218, 308, 419 and 565 nm, respectively. The mechanical and thermal stresses in these nickel-coated optical fibers are analyzed. The atomic force microscope measurement reveals that the roughness of the nickel coating is unchanged when the coating thickness is not larger than 65 nm. However, as the coating thickness is not less than 65 nm, the coating roughness increases with increasing the coating thickness. To increase the tensile strength of the nickel-coated optical fiber, the coating thickness should be not less than 65 nm, and the surface roughness of the nickel coating should not exceed 2.93 nm. Alternatively, if the coating thickness is in the range of 35 to 218 nm, thermally induced stress voids are less found in the nickel coatings. However, if the coating thickness is in the range of 308 to 565 nm, the number of thermally induced stress voids increases with increasing the coating thickness. To minimize these voids, the surface roughness of the nickel coating should also be decreased.

Macromolecules, Sep 3, 2004

... first term on the right-hand side represents the entropic constraint of the molecular network... more ... first term on the right-hand side represents the entropic constraint of the molecular network, and the ... model can be proposed by applying a time-dependent boundary condition in the existingmodel. 15 Consider a PET film of thickness 2l and the film area much larger than the ...

ECS Journal of Solid State Science and Technology, 2013

The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To ... more The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5∼7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeO x (3 nm)/Fe(3 nm)/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeO x and Fe/FePt layers was decoupled. The moments in FeO x layer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500 ∘ C and 800 ∘ C for 3 minutes. When the FeO x (3 nm)/Fe(3 nm)/FePt trilayer was annealed at 500 ∘ C, the layers structure was changed to FeO x (6 nm)/FePt bilayer due to oxygen diffusion. The hard-magnetic FeO x (6 nm)/FePt film was coupled with single switching field. The FeO x /(disordered FePt) layer structure was observed with further annealing at 800 ∘ C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeO x layer, and hard-magnetic L1 0 FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L1 0 FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800 ∘ C.

Solar Energy Materials and Solar Cells, 2015

The effect of the thin native silicon dioxide (SiO 2) interfacial layer on the photovoltaic chara... more The effect of the thin native silicon dioxide (SiO 2) interfacial layer on the photovoltaic characteristics of gold/p-type amorphous boron carbon thin film alloy/silicon dioxide/n-type silicon/aluminum (Au/a-BC/ SiO 2 /n-Si/Al) solar cells is investigated. a-BC thin film alloy was deposited on n-Si substrate with an SiO 2 layer using a reactive sputtering system. The front and back surfaces of this a-BC/SiO 2 /n-Si solar cell were covered with Au and Al electrodes, respectively. a-BC thin film alloys and Au/a-BC/SiO 2 /n-Si/Al solar cells were annealed at 623 K in an atmosphere of argon. Raman spectra and X-ray photoelectron spectroscopy results show that the a-BC thin film alloy has a D band and a G band and the boron/carbon ratio is 12.4%. The optical band gap and electrical resistivity of the a-BC thin film alloy are 1.90 eV and 7.73 Â 10 4 Ω m, respectively. Under illumination at 1000 W/m 2 , the Au/a-BC/SiO 2 /n-Si/Al solar cell exhibits a shortcircuit current density, open-circuit voltage, fill factor, and power conversion efficiency of 165 A/m 2 , 0.22 V, 0.904, and 3.3%, respectively. Remarkably, the Au/a-BC/SiO 2 /n-Si/Al solar cell has a fill factor of 0.934 at an illumination intensity of 200 W/m 2 , which exceeds any value obtained to date. The thin SiO 2 layer improves the photovoltaic characteristics of Au/a-BC/SiO 2 /n-Si/Al solar cells, and the reasons for this improvement are discussed herein.

IET Optoelectronics, 2015

The viscoelastic behaviour of commercial polymeric coatings for optical fibres is measured at roo... more The viscoelastic behaviour of commercial polymeric coatings for optical fibres is measured at room temperature using dynamic mechanic analysis, and the relationship between strain and stress in polymeric coatings is obtained. The thermally induced viscoelastic stresses in dual-coated optical fibres are derived from the viscoelastic behaviour of commercial polymeric coatings. The compressive radial stress on the glass fibre surface produces microbending losses, which can be diminished by properly choosing the thickness and material properties of polymeric coatings. The design of dual-coated optical fibres to diminish thermally induced microbending losses caused by viscoelastic behaviour of polymeric coatings is proposed. The thermally induced microbending loss in dual-coated optical fibres evaluated by Maxwell model is underestimated.

Surface and Coatings Technology, 2010

Abstract The effects of deposition parameters on characteristics of carbon coatings on optical fi... more Abstract The effects of deposition parameters on characteristics of carbon coatings on optical fibers prepared by thermal chemical vapor deposition are investigated. The deposition parameters are selected as follows. The CH 4 /(CH 4 + N 2 ) ratio is in the range between 20% and 100%; the temperature is set from 1173 to 1248 K; the working pressure is arranged between 50 and 100 kPa, and the residence time is ranging from 1.47 to 7.37 s. The deposition rate, microstructure, and electrical resistivity of carbon coatings are measured. The low-temperature surface morphology of carbon-coated optical fibers is elucidated. Experimental results indicate that the deposition rate increases with increasing the CH 4 /(CH 4 + N 2 ) ratio, deposition temperature, working pressure, and residence time. The activation energy (= 456 kJ/mol) of carbon deposition from methane was shown to correlate to the activation energy of methane dissociation. The deposition rate is proportional to about first-order of partial pressure of methane, and thus, the deposition process is mainly controlled by the process to create mono-carbon species in the carbon film. As the deposition rate increases, the size and number of particles on the carbon coating surface and electrical resistivity of carbon coatings increase, while the ordered degree, nano-crystallite size, and sp 2 carbon atoms of the carbon coatings decrease. Additionally, the low-temperature surface morphology of carbon coatings shows that as the carbon coating thickness is large enough to sustain the thermal loading, decreasing the deposition rate is good for producing hermetic optical fiber coatings.

Journal of Materials Research, Aug 1, 1993

Based on the results of Shiue and Lee [J. Appl. Phys. 70, 2947 (1991)], the effect of plastic zon... more Based on the results of Shiue and Lee [J. Appl. Phys. 70, 2947 (1991)], the effect of plastic zone and grain boundary on the dislocation emission criterion was investigated. The emission criterion is based on the concept of spontaneous emission. The critical stress intensity factor for dislocation emission increases with the increasing size of dislocation-free zone and the number of piled-up dislocations in the plastic zone, but decreases with increasing grain size. The ductile versus brittle behavior of material was determined by the competition of critical stress intensity factors for dislocation emission and crack propagation. A material with larger grain size is easier to emit dislocation and allows more dislocations to be piled up, so that it behaves more ductile.

Philosophical Magazine A, Jun 1, 1993

Abstract Dislocations piled up between a finite crack tip and a grain boundary ledge with a dislo... more Abstract Dislocations piled up between a finite crack tip and a grain boundary ledge with a dislocation-free zone are investigated by a continuous dislocation modelling method. The dislocation distribution function to simulate the crack and plastic zone is analytically derived. A closed form for the number of dislocations in the plastic zone is analytically derived. A closed form for the number of dislocations in the plastic zone and stress field is obtained. From the stress field, the stress intensity factor K m and stress concentration at the grain boundary are obtained. When there is no dislocation-free zone in front of crack tip, the stress intensity factor K m is zero, no matter whether the grain boundary exists or not. The effect of the grain boundary ledge on the fracture toughness and the effect of the crack on the strength of the grain boundary, such as described by the Hall-Petch equation, are discussed. Finally, our results can reduce to several special cases, and these are discussed.

International Journal of Fracture, 1995

The elastic interaction between an edge dislocation and two collinear internal cracks of differen... more The elastic interaction between an edge dislocation and two collinear internal cracks of different length has been investigated. The effect of the distance between two collinear cracks on the crack shielding and image force on the edge dislocation were examined. The effect of the length of the right-hand-side crack on the shielding of the left-hand-side crack and the image force

Applied Physics Letters, Mar 13, 2006

Electrical performance was found to be closely related to the variation of nanosized interface mo... more Electrical performance was found to be closely related to the variation of nanosized interface morphology in previous studies. This work investigated in detail the microstructural development of in-and anti-phase bonded interfaces for n-type ͑100͒ GaAs wafers treated at 500, 600, 700 and 850°C. The interfacial energy of anti-phase bonding is higher than that of in-phase bonding based on the first-principles calculations. The higher interface energy tends to stabilize the interfacial oxide layer. The continuous interfacial oxide layer observed below 700°C can deteriorate the electrical property due to its insulating property. However, the existence of nanoscaled oxide at anti-phase bonded interfaces can improve the electrical conductivity at 700°C. This is due to the suppression of the evaporation of As atom by the interfacial nanoscaled oxides based on the analysis of autocorrelation function and energy dispersive x-ray spectroscopy.

Materials Chemistry and Physics, Feb 1, 2004

The effect of polymeric coatings on the static fatigue of tightly jacketed double-coated optical ... more The effect of polymeric coatings on the static fatigue of tightly jacketed double-coated optical fibers is theoretically analyzed. A closed form solution of the tensile stress in the glass fiber is obtained from viscoelastic theory. The tensile stress in the glass fiber in the static fatigue test increases with time due to the viscoelastic behavior of the polymeric coatings, and this increase will accelerate the failure of the optical fiber. The long-term strength of optical fibers can be improved by increasing the axial rigidities and the relaxation times of the secondary coating and the tight jacket. Finally, a rule to prevent the overestimation of fiber's lifetimes in the static fatigue test is proposed.

Thin Solid Films, Apr 1, 2014

The properties of carbon films prepared by thermal chemical vapor deposition (thermal CVD) using ... more The properties of carbon films prepared by thermal chemical vapor deposition (thermal CVD) using camphor are investigated. As the deposition temperature increases from 1098 to 1198 K, the deposition rate follows the Arrhenius law with activation energy of 59.8 kJ/mol. The possible reaction paths and intermediate species of this thermal CVD process are also considered. The product gases CH 3 , CH 4 , and C 2 H 2 can be speculated as the main species for pyrolytic carbon deposition. The crystallinity and ordering degree of carbon films decrease with increasing the deposition temperature. Nevertheless, the sp 2 carbon sites increase with increasing the deposition temperature, and results in the decrease of electrical resistivity and the increase of water contact angle. When the camphor weight changes from 0.06 to 0.50 g, the CVD reaction is controlled by a process of half order. Moreover, as the camphor weight increases from 0.30 to 0.50 g, the surfaces of carbon films are partially covered with spherical particles, the water contact angle substantially increases. Finally, the results of this work are compared to those of using CH 4 and C 2 H 2 as the precursor gases.

Journal of Applied Physics, Sep 1, 2010

The viscoelastic behavior of commercial UV-cured polymeric coatings of optical fibers is evaluate... more The viscoelastic behavior of commercial UV-cured polymeric coatings of optical fibers is evaluated using dynamic mechanic analysis. The results indicate that relaxation of stresses and/or strains in these coatings occurs by creep deformation. The axial strain-induced viscoelastic stresses in optical fibers are derived from the exact viscoelastic behavior of the polymeric coatings. Compressive radial stress on the glass fiber produces microbending losses, and therefore, microbending losses in double-coated optical fibers that are caused by axial strain-induced creep deformation of polymeric coatings are investigated. These microbending losses can be minimized by suitably selecting the thickness and physical properties of the polymeric coatings, as follows. The radius, Poisson’s ratio, and strain ratio of the primary coating should be increased, but the Young’s modulus and relaxation time of the primary coating should be decreased. The radius, Young’s modulus, Poisson’s ratio, and strain ratio of the secondary coating should be decreased, but the relaxation time of the secondary coating should be increased. When the thickness and physical properties of the polymeric coating are chosen to minimize the microbending loss, the thickness and Young’s modulus of the secondary coatings should be large enough to withstand an external mechanical force.

ECS Journal of Solid State Science and Technology, 2013

The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To ... more The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5∼7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeO x (3 nm)/Fe(3 nm)/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeO x and Fe/FePt layers was decoupled. The moments in FeO x layer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500 ∘ C and 800 ∘ C for 3 minutes. When the FeO x (3 nm)/Fe(3 nm)/FePt trilayer was annealed at 500 ∘ C, the layers structure was changed to FeO x (6 nm)/FePt bilayer due to oxygen diffusion. The hard-magnetic FeO x (6 nm)/FePt film was coupled with single switching field. The FeO x /(disordered FePt) layer structure was observed with further annealing at 800 ∘ C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeO x layer, and hard-magnetic L1 0 FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L1 0 FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800 ∘ C.

Optical Engineering, Jun 1, 2002

The design of tightly jacketed double-coated optical fibers to minimize long-term hydrostatic-pre... more The design of tightly jacketed double-coated optical fibers to minimize long-term hydrostatic-pressure-induced microbending losses is investigated. Microbending loss in these fibers is dominated by compressive radial stress at the interface between the glass fiber and the primary coating, which is a function of the polymeric materials properties and their thicknesses. To minimize the long-term hydrostatic-pressure-induced microbending losses, one should decrease

Journal of Applied Physics, Sep 1, 2004

This study theoretically investigates the effect of temperature cycling on the static fatigue of ... more This study theoretically investigates the effect of temperature cycling on the static fatigue of double-coated optical fibers. The tensile force and temperature cycling induced tensile stresses on the glass fiber of double-coated optical fibers are determined using the viscoelastic theory. Optical fibers lifetime is dominated by the tensile stress on the glass fibers, which is a function of the material properties and thickness of the polymeric coating. To minimize these stresses on the glass fiber, the radius, Young’s modulus, and thermal expansion coefficient of the secondary coating should be reduced, while the relaxation time of the secondary coating should be increased. Additionally, based on strength consideration, the radius and Young’s modulus of the polymeric coating should be sufficiently thick or hard to support the external mechanical stresses. Meanwhile, based on the microbending-insensitivity consideration, the relaxation time of the primary coating should be reduced.

Journal of Lightwave Technology, 2003

The design of double-coated optical fibers to minimize long-term tensile-force-induced delaminati... more The design of double-coated optical fibers to minimize long-term tensile-force-induced delamination of polymeric coatings from glass fibers is investigated using viscoelastic theory. To prevent the delamination of polymeric coatings from glass fibers, the tensile-force-induced interfacial shear stress between the glass fiber and primary coating should be always smaller than its interfacial shear strength in the long term. The tensile-force-induced interfacial

Optical Engineering, Apr 1, 2008

Growth of conical particles in carbon films deposited on silica glass fibers prepared by thermal ... more Growth of conical particles in carbon films deposited on silica glass fibers prepared by thermal chemical vapor deposition is investigated. The results show that the size and number of conical particles on the silica glass fiber increase with the film thickness and deposition temperature, but this effect is reduced when the carbon films are deposited on silica glass plates. The growth of conical particles on the silica glass fiber is mainly due to the small cross-sectional area of the fibers. These conical particles are against the hermetic property of carbon-coated optical fibers. We propose a method to minimize conical particles in carbon films on silica glass fibers.

Optical Engineering, Mar 1, 2007

The effects of annealing on the properties of hermetically carbon-coated optical fibers are inves... more The effects of annealing on the properties of hermetically carbon-coated optical fibers are investigated. The hermetically carbon-coated optical fibers are prepared by the plasma enhanced chemical vapor deposition method using methane and hydrogen as the precursor gases. The annealing temperatures are selected at 100, 200, 300, 400, and 500°C, respectively. The thickness, optical band gap, and microstructure of carbon films are measured. Meanwhile, the water-repellency and low-temperature surface morphology of carbon-coated optical fibers are evaluated. The results indicate that the thickness and defect content of the carbon films decrease with increasing the annealing temperature, while the degree of structure order and the amount of microcrystalline graphite in the carbon films increase. When the annealing temperature is over 300°C, the carbon films acquire enough thermal energy to cause a great amount of hydrogen and hydrocarbon to be released, and the carbon films transform to the graphitelike structure. Additionally, based on the evaluation of water-repellency and low temperature–induced break or delamination of carbon films, it is found that the carbon film annealed at 300°C is the best one for use as the hermetic optical fiber coating.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Jun 1, 1989

The elastic interaction between a screw dislocation and a welded surface crack in a thin plate of... more The elastic interaction between a screw dislocation and a welded surface crack in a thin plate of composite material has been analysed using the conformal mapping technique. The effect of size on fracture is pronounced when the ratio of thickness to crack length is less than 10. However, when it exceeds 10, the problem can be simply treated as that of a semi-infinite composite material Whether dislocation emission occurs at the tip also depends on the size of the specimen and the shear modulus ratio. The dislocation can be emitted more easily from the crack tip into the soft phase than into the hard one. The emitted angle of dislocation for minimal critical stress intensity factor increases with the shear modulus ratio. In addition, the results can be applied to several special cases. Finally, when the boundary value is not zero, such as in an applied stress, the mapping function must be selected carefully.

Thin Solid Films, Aug 1, 2005

The effect of the coating thickness and roughness on the mechanical strength and thermally induce... more The effect of the coating thickness and roughness on the mechanical strength and thermally induced stress voids in nickel-coated optical fibers is theoretically and experimentally investigated. Seven samples of nickel-coated optical fibers with identical fiber length but different coating thickness are prepared using electroless plating method. The thickness of the nickel coating is controlled by the plating time, with the thicknesses being 35, 65, 119, 218, 308, 419 and 565 nm, respectively. The mechanical and thermal stresses in these nickel-coated optical fibers are analyzed. The atomic force microscope measurement reveals that the roughness of the nickel coating is unchanged when the coating thickness is not larger than 65 nm. However, as the coating thickness is not less than 65 nm, the coating roughness increases with increasing the coating thickness. To increase the tensile strength of the nickel-coated optical fiber, the coating thickness should be not less than 65 nm, and the surface roughness of the nickel coating should not exceed 2.93 nm. Alternatively, if the coating thickness is in the range of 35 to 218 nm, thermally induced stress voids are less found in the nickel coatings. However, if the coating thickness is in the range of 308 to 565 nm, the number of thermally induced stress voids increases with increasing the coating thickness. To minimize these voids, the surface roughness of the nickel coating should also be decreased.

Macromolecules, Sep 3, 2004

... first term on the right-hand side represents the entropic constraint of the molecular network... more ... first term on the right-hand side represents the entropic constraint of the molecular network, and the ... model can be proposed by applying a time-dependent boundary condition in the existingmodel. 15 Consider a PET film of thickness 2l and the film area much larger than the ...

ECS Journal of Solid State Science and Technology, 2013

The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To ... more The Fe(6 nm)/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5∼7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeO x (3 nm)/Fe(3 nm)/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeO x and Fe/FePt layers was decoupled. The moments in FeO x layer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500 ∘ C and 800 ∘ C for 3 minutes. When the FeO x (3 nm)/Fe(3 nm)/FePt trilayer was annealed at 500 ∘ C, the layers structure was changed to FeO x (6 nm)/FePt bilayer due to oxygen diffusion. The hard-magnetic FeO x (6 nm)/FePt film was coupled with single switching field. The FeO x /(disordered FePt) layer structure was observed with further annealing at 800 ∘ C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeO x layer, and hard-magnetic L1 0 FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L1 0 FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800 ∘ C.

Solar Energy Materials and Solar Cells, 2015

The effect of the thin native silicon dioxide (SiO 2) interfacial layer on the photovoltaic chara... more The effect of the thin native silicon dioxide (SiO 2) interfacial layer on the photovoltaic characteristics of gold/p-type amorphous boron carbon thin film alloy/silicon dioxide/n-type silicon/aluminum (Au/a-BC/ SiO 2 /n-Si/Al) solar cells is investigated. a-BC thin film alloy was deposited on n-Si substrate with an SiO 2 layer using a reactive sputtering system. The front and back surfaces of this a-BC/SiO 2 /n-Si solar cell were covered with Au and Al electrodes, respectively. a-BC thin film alloys and Au/a-BC/SiO 2 /n-Si/Al solar cells were annealed at 623 K in an atmosphere of argon. Raman spectra and X-ray photoelectron spectroscopy results show that the a-BC thin film alloy has a D band and a G band and the boron/carbon ratio is 12.4%. The optical band gap and electrical resistivity of the a-BC thin film alloy are 1.90 eV and 7.73 Â 10 4 Ω m, respectively. Under illumination at 1000 W/m 2 , the Au/a-BC/SiO 2 /n-Si/Al solar cell exhibits a shortcircuit current density, open-circuit voltage, fill factor, and power conversion efficiency of 165 A/m 2 , 0.22 V, 0.904, and 3.3%, respectively. Remarkably, the Au/a-BC/SiO 2 /n-Si/Al solar cell has a fill factor of 0.934 at an illumination intensity of 200 W/m 2 , which exceeds any value obtained to date. The thin SiO 2 layer improves the photovoltaic characteristics of Au/a-BC/SiO 2 /n-Si/Al solar cells, and the reasons for this improvement are discussed herein.

IET Optoelectronics, 2015

The viscoelastic behaviour of commercial polymeric coatings for optical fibres is measured at roo... more The viscoelastic behaviour of commercial polymeric coatings for optical fibres is measured at room temperature using dynamic mechanic analysis, and the relationship between strain and stress in polymeric coatings is obtained. The thermally induced viscoelastic stresses in dual-coated optical fibres are derived from the viscoelastic behaviour of commercial polymeric coatings. The compressive radial stress on the glass fibre surface produces microbending losses, which can be diminished by properly choosing the thickness and material properties of polymeric coatings. The design of dual-coated optical fibres to diminish thermally induced microbending losses caused by viscoelastic behaviour of polymeric coatings is proposed. The thermally induced microbending loss in dual-coated optical fibres evaluated by Maxwell model is underestimated.

Surface and Coatings Technology, 2010

Abstract The effects of deposition parameters on characteristics of carbon coatings on optical fi... more Abstract The effects of deposition parameters on characteristics of carbon coatings on optical fibers prepared by thermal chemical vapor deposition are investigated. The deposition parameters are selected as follows. The CH 4 /(CH 4 + N 2 ) ratio is in the range between 20% and 100%; the temperature is set from 1173 to 1248 K; the working pressure is arranged between 50 and 100 kPa, and the residence time is ranging from 1.47 to 7.37 s. The deposition rate, microstructure, and electrical resistivity of carbon coatings are measured. The low-temperature surface morphology of carbon-coated optical fibers is elucidated. Experimental results indicate that the deposition rate increases with increasing the CH 4 /(CH 4 + N 2 ) ratio, deposition temperature, working pressure, and residence time. The activation energy (= 456 kJ/mol) of carbon deposition from methane was shown to correlate to the activation energy of methane dissociation. The deposition rate is proportional to about first-order of partial pressure of methane, and thus, the deposition process is mainly controlled by the process to create mono-carbon species in the carbon film. As the deposition rate increases, the size and number of particles on the carbon coating surface and electrical resistivity of carbon coatings increase, while the ordered degree, nano-crystallite size, and sp 2 carbon atoms of the carbon coatings decrease. Additionally, the low-temperature surface morphology of carbon coatings shows that as the carbon coating thickness is large enough to sustain the thermal loading, decreasing the deposition rate is good for producing hermetic optical fiber coatings.