Browsing by Author "Chiu, Chia-Hsiang"

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Formation mechanisms and atomic configurations of nitride phases at the interface of aluminum nitride and titanium
(2008-08-01)
Chiu, Chia-Hsiang
;
Lin, Chien-Cheng
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材料科學與工程學系
;
Department of Materials Science and Engineering
Aluminum nitride was bonded with a titanium foil at 1400 degrees C for up to 1 h in Ar. The AlN/Ti interfacial reactions were investigated using analytical electron microscopy. Reaction layers, consisting of delta-TiN, tau(2)-Ti2AlN, gamma-TiAl, alpha(2)-Ti3Al, a two-phase region (alpha(2)-Ti3Al + alpha-Ti), and alpha-Ti (Al, N) solid solution, were observed after annealing at 1400 degrees C for 0.1 h. Among these phases, the alpha(2)-Ti3Al and (alpha(2)-Ti3Al + alpha-Ti) were formed during cooling. Further diffusion of N atoms into the reaction zone precipitates a chopped fiber-like alpha(2)-Ti2AlN in the matrix of gamma-TiAl, with [110](gamma-TiAl)//[11 (2) over bar0](tau 2-Ti2AlN) and (1 (1) over bar(1) over bar)(gamma-TiAl)//(1 (1) over bar0 (3) over bar)(tau 2-Ti2AlN), by substituting N atoms for one-half Al atoms after annealing at 1400 degrees C for 1 h. The released Al atoms, due to the precipitation Of tau(2)-Ti2AlN, resulted in an ordered Al-rich gamma-TiAl or Ti3Al5. Furthermore, the alpha-Ti (Al, N) was nitridized into a lamellar layer (delta-TiN + alpha-Ti) with [110](delta-TiN)//[11 (2) over bar0](alpha-Ti) and (111)(delta-TiN)//(0001)(alpha-Ti).
Microstructural development of the AlN/Ti diffusion couple annealed at 1000 degrees C
(2008-04-01)
Chiu, Chia-Hsiang
;
Lin, Chien-Cheng
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The microstructural development of an AlN/Ti diffusion couple, annealed at 1000 degrees C in an argon atmosphere for 0.1-36 h, was investigated using analytical scanning electron microscopy and transmission electron microscopy. The decomposition and diffusion of Al and N atoms into Ti gave rise to various reaction layers at the interface. A delta-TiN layer was initially formed in the reaction zone between AlN and Ti, and the alpha(2)-Ti3Al layer subsequently developed between delta-TiN and Ti. Then an intergranular tau(1)-Ti3AlN phase was formed in the delta-TiN layer with the orientation relationships [111](tau 1)- Ti-3 AlN//[111](delta- TiN) and (1 (1) over bar0)(tau 1)-Ti-3 AlN//(1 (1) over bar0)(delta- TiN). The further diffusion of N atoms into the alpha(2)-Ti3Al layer led to the growth of delta-TiN and a twinned alpha(2)-Ti3Al(N) solid solution, wherein N atoms went to one of the octahedral interstitial sites in an orderly manner upon cooling, resulting in the formation of tau(1)-Ti3AlN. The orientation relationships between tau(1)-Ti3AlN and alpha(2)-Ti3Al(N) were [111](tau 1)- Ti-3 AlN// [0001](alpha 2)- Ti3Al(N) and (0 (1) over bar1)(tau 1)- Ti3AlN//((1) over bar(1) over bar 20)(alpha 2)- Ti3Al(N). Finally, diffusion paths are proposed for the interfacial reactions at various stages.
Taper-integrated multimode-interference based crossings for silicon wire waveguides
(2010)
Chiu, Chia-Hsiang
;
Chen, Chyong-Hua
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光電工程學系
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Department of Photonics
Novel multimode-interference (MMI)-based crossings integrated with miniaturized tapers are numerically presented for Silicon wire waveguides. These miniature tapers function as field expanders to reduce transition loss between the input/output waveguide and the MMI region and the crosstalk in the crossing section. As a consequence, the lengths of MMI sections reduce to less than twice of the beat length. Using finite different time domain method, we demonstrate that the MMI-based waveguide crossing embedded in the quadratic tapers has the size of 5800x5800 nm(2), the insertion loss of 0.15 dB and the crosstalk of -42 dB at the wavelength of 1550 nm and broad transmission spectrum ranging from 1500 nm to 1600 nm.
Taper-Integrated Multimode-Interference Based Waveguide Crossing Design
(2010-11-01)
Chen, Chyong-Hua
;
Chiu, Chia-Hsiang
;
光電工程學系
;
Department of Photonics
We present a design technique for a compact waveguide crossing by using a 90 multimode-interference (MMI) based waveguide crossing sandwiched by four identical miniaturized tapers where the power of the input guided mode is coupled into even modes of the MMI section at a specific power ratio and with different phases, thereby reducing the dimension of this waveguide crossing with imperceptible loss and crosstalk. Using the finite difference time domain method, we demonstrate that the MMI-based waveguide crossing embedded in short Gaussian tapers has a size 5426 nm x 5426 nm, insertion loss 0.21 dB, and crosstalk -44.4 dB at the wavelength of 1550 nm and broad transmission spectrum ranging from 1500 to 1600 nm.