Browsing by Issue Date, starting with "1996-01-29"

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Effect of rapid thermal annealing on the electrical and physical properties of metalorganic chemical-vapor-deposited TiN
(1996-01-29)
Sun, SC
;
Tsai, MH
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奈米中心
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Nano Facility Center
This work reports on the effect of postdeposition thermal treatment using rapid thermal annealing on the physical and electrical properties of metalorganic chemical-vapor-deposited (MOCVD) titanium nitride (TiN) thin films. When ammonia is used as the annealing ambient, the resistivity decreases with increasing annealing temperature. The resistivity of MOCVD TiN was reduced from 6000 to 320 mu Omega cm after 800 degrees C rapid thermal annealing in ammonia (RTN). Annealing in nitrogen ambient was found to be not nearly as effective as that in ammonia. The decrease in resistivity may be attributed to a reduction in the carbon and oxygen content, growth in grain size through polycrystalline recrystallization, as well as to an increase in film density. (C) 1995 American Institute of Physics.
Effect of thermal annealing on electrical conductivities in arsenic-ion-implanted GaAs
(1996-01-29)
Chen, WC
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Chang, CS
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交大名義發表
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光電工程學系
;
National Chiao Tung University
The effect of thermal annealing on the electrical conductivities of arsenic-ion-implanted GaAs has been investigated by deep level transient spectroscopy and temperature-dependent conductance measurements. For the annealed films of arsenic-ion-implanted GaAs a band of deep-level defects with the activation energy of around 0.55 eV below the conduction band is found. The dense concentration of traps is able to reduce the carrier concentration from 3 X 10(18) to 2 X 10(17) cm(-3). The cross section of the deep level is calculated to be 1.5 X 10(-14) cm(2). The carrier-transport mechanisms of both as-implanted GaAs and postannealed GaAs are dominantly shown to be a separate hopping and active-type conduction. (C) 1996 American Institute of Physics.
An algorithm for inverting rational matrices
(1996-01-31)
Lin, CA
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Yang, CW
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Hsieh, TF
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交大名義發表
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電控工程研究所
We propose an algorithm for computing the inverses of rational matrices and in particular the inverses of polynomial matrices. The algorithm is based on minimal state space realizations of proper rational matrices and the matrix inverse lemma and is implemented as a MATLAB function. Experiments show that the algorithm gives accurate results for typical rational matrices that arise in analysis and design of linear multivariable control systems. Illustrative examples are given.
A study on blends of liquid crystalline copolyesters with polycarbonate .2. Transesterification control
(1996-01-31)
Wei, KH
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Su, KF
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交大名義發表
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材料科學與工程學系
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National Chiao Tung University
The inhibited and catalyzed ester exchange (transesterification) during melt blending of poly(bisphenol-A carbonate) (PC) and liquid crystalline poly(oxybenzoate-co-ethylene terephthalate) (POB-PET 40/60; P46) was investigated with differential scanning calorimetry. It was found that the ester exchange between P46 and PC was effectively inhibited for a 20% P46 blend at 240 degrees C, as further confirmed by nuclear magnetic spectroscopy. When the blending temperature and P46 concentration increased, only the transesterification between the PET segment in P46 and PC took place under inhibition. The morphology of the blends was analyzed with scanning electron microscopy and displayed a disconnected interface between P46 and PC under inhibition. Conversely, the transesterification took place between the POB segment in P46 and PC when a catalyst was added. (C) 1996 John Wiley & Sons, Inc.
Effect of oxygen concentration in the sputtering ambient on the microstructure, electrical and optical properties of radio-frequency magnetron-sputtered indium tin oxide films
(1996-02-01)
Wu, WF
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Chiou, BS
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Indium tin oxide (ITO) films have been prepared by radio-frequency (rf) magnetron sputtering. The effect oi oxygen concentration in the sputtering ambient on the structure and properties oi ITO films are investigated. The films have a preferred orientation in the (440) plane. The presence of oxygen during sputtering enhances the crystallization of the film. Film grain size increases as more oxygen is added. According to the XPS measurements, the addition of oxygen reduces the oxygen-deficient region of the film. Hence the optical transmittance of the film is improved while film conductivity decreases.
Detection of coherent signals using weighted subspace smoothing
(1996-02-01)
Ma, CW
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Teng, CC
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交大名義發表
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電控工程研究所
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National Chiao Tung University
A new approach to detecting the number of coherent signals incident upon a uniformly-spaced linear array is presented. The approach combines a modified spatial smoothing scheme and a modified MDL criterion. The modified spatial smoothing scheme, referred to as ''weighted subspace smoothing,'' is actually a generalization of the ''post-smoothing'' approach proposed by Krim and Proakis in 1994. It is shown that the noise eigenvalues obtained with weighted subspace smoothing are more accurate than those obtained with the original spatial smoothing. We thus attempt to improve detection performance using these more accurate eigenvalues. A novel modification of the minimum description length (MDL) criterion is proposed to accomplish this. Computer simulations are presented to study the performance improvement of this new approach.
An efficient improvement for barrier effect of W-filled contact
(1996-02-01)
Yeh, WK
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Chan, KY
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Chang, TC
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Tsai, MH
;
Chen, SH
A post chemical vapor deposition of tungsten (CVD-W) treatment by N-2 plasma is proposed to suppress the WAl12 formation during subsequent thermal annealing, which improves the thermal stability of W-filled contact. Selective CVD-W is employed to fill the contact hole. Following W deposition, in situ N-2 plasma treatment is performed prior to Al alloy metallization. It is shown that this post CVD-W treatment efficiently suppresses the formation of WAl12, resulting in an improvement of the barrier capability of W-filled contact.
The surface effect on Au 4f X-ray photoelectron spectra
(1996-02-01)
Wang, JP
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Tung, CJ
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Chen, YF
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Kwei, CM
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電子工程學系及電子研究所
An investigation of the surface effect on Au 4f X-ray photoelectron spectra was made for different emission angles, It was found that surface plasmon excitations made significant contributions to the spectra in single and plural energy-loss peaks and in the multiple loss background, Our approach involved Monte Carlo simulations of photoelectrons in the interior region of the solid and Poisson stochastic processes in the surface region. The partial-wave expansion method with the Hartree-Fock-Wigner-Seitz potential for the solid was used to calculate differential electron elastic scattering cross sections. An extended Drude dielectric function model was employed to compute electron differential inverse mean free paths for volume excitations. The inelastic mean free paths in the surface region became spatially-varying and were calculated. Differential probabilities for surface excitations were determined using the same model dielectric function. The computed X-ray photoelectron spectra including surface excitations agreed quite well with experimental data.
Quadrilevel periodic sequences for fast start-up equalization and channel estimation
(1996-02-01)
Liu, GS
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Wei, CH
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電控工程研究所
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Institute of Electrical and Control Engineering
A class of four-level periodic sequences derived from the binary m-sequences are presented. These sequences can be used as the training sequences in adaptive channel estimation and equalization with fast start-up for multilevel PAM or QAM transmission. The sequence generator can be implemented by simple hardware.
Relation-based variations of the discrete radon transform
(1996-02-01)
Hsueh, YC
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交大名義發表
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資訊工程學系
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National Chiao Tung University
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Department of Computer Science
The finite Radon transform was introduced by Bolker around 1976. Since then, many variations of the discrete Radon transform have been proposed. In this paper, we first propose a variation of the discrete Radon transform which is based on a binary relation. Then, we generalize this variation to weighted Radon transformation based on a weighted relation. Under such generalization, we show that discrete convolution is a special case of weighted Radon transformation. To further generalize Radon transformation to be defined on lattice-valued functions, we propose two nonlinear variations of Radon transformation. These two nonlinear variations have very close relations with morphological operations. Finally, we generalize Matheron's representation theorem to represent translation-invariant operations on functions from an abelian group to a complete lattice.
Formation of cobalt silicided shallow junction using implant into through silicide technology and low temperature furnace annealing
(1996-02-01)
Chen, BS
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Chen, MC
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This work investigates the shallow CoSi2 contacted junctions formed by BF2+ and As+ implantation, respectively, into/through cobalt silicide followed by low temperature furnace annealing, For p(+)n junctions fabricated by 20 keV BF2+ implantation to a dose of 5 x 10(15) cm(-2), diodes with a leakage current density less than 2 nA/cm(2) at 5 V reverse bias can be achieved by a 700 degrees C/60 min annealing. This diode has a junction depth less than 0.08 mu m measured from the original silicon surface, For n(+)p junctions fabricated by 40 keV As+ implantation to a dose of 5 x 10(15) cm(-2), diodes with a leakage current density less than 5 nA/cm(2) at 5 V reverse bias can be achieved by a 700 degrees C/90 min annealing; the junction depth is about 0.1 mu m measured from the original silicon surface. Since the As+ implanted silicide film exhibited degraded characteristics, an additional fluorine implantation was conducted to improve the stability of the thin silicide film, The fluorine implantation can improve the silicide/silicon interface morphology, but it also introduces extra defects. Thus, one should determine a tradeoff between junction characteristics, silicide film resistivity, and annealing temperature.
Characterization of anodic aluminum oxide film and its application to amorphous silicon thin film transistors
(1996-02-01)
Liang, CW
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Luo, TC
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Feng, MS
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Cheng, HC
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Su, D
AL(2)O(3)/SINx double-layered dielectric films suitable for large-size amorphous silicon thin film transistor liquid crystal displays (a-Si:H TFT LCD) have been prepared by anodization and plasma enhanced chemical vapor deposition (PECVD). Al2O3 films were formed at various pH values and volume ratio of water (H2O%) in the electrolyte. The optimal quality of Al2O3 film was achieved at pH = 6 and H2O% = 30. These high-quality Al2O3 films have denser structure, lower etching rate (90 Angstrom min(-1)) and smooth surface morphology after etching. The capacitors made of the anodization show a breakdown field as high as 7.8 MV cm(-1) and a low leakage current density of 10 nA cm(-2) at a dielectric field of 3 MV cm(-1). Furthermore, a-Si:H TFTs with Al gate and different gate dielectrics (Al2O3/SINx and SiNx) were also fabricated and evaluated. The TFTs with Al2O3/SiNx double-layered gate dielectric provide better performances, such as the smaller threshold voltage (1.76 V), improved subthreshold swing (1.0 V dec(-1)), and lower off-current (3.8 PA) than those of the device with single SiNx, film.
Finite element modelling for land displacements due to pumping
(1996-02-01)
Yeh, HD
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Lu, RH
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Yeh, GT
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土木工程學系
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環境工程研究所
Equations of equilibrium (force balance) and flow in multidimensions were coupled in this paper to describe land displacements due to pressure decline in aquifers. A Galerkin finite element model based on these equations was developed. The saturated/unsaturated behaviour and the isotropic/anisotropic properties of permeability and elasticity were considered when the model was formulated. This model was verified by comparing its simulation results with those of known analytical solutions for simplified cases. The simulation of displacements due to pressure decline in unsaturated media was also performed. Those results demonstrated that the choice of boundary ranges for an aquifer with infinite domain may significantly affect the estimated horizontal and vertical displacements. To obtain a good estimation of land displacements, the boundary ranges should be carefully chosen. The displacements occurring in unconfined aquifers are caused by the drop of the water table and the change in body force in the dewatering zone. Simulation results also indicated that the change in body force should be considered once an unconfined aquifer has been pumped. Otherwise, the horizontal and vertical displacements in unconfined aquifers would be overestimated and underestimated, respectively. The behaviour of land displacements due to pumping was shown to be affected by changes in the total stresses in aquifers.
Unstable aiding and opposing mixed convection of air in a bottom-heated rectangular duct slightly inclined from the horizontal
(1996-02-01)
Lin, WL
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Lin, TF
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交大名義發表
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機械工程學系
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National Chiao Tung University
Buoyancy-induced secondary vortex and reverse flows, flow transition, and the associated heat transfer processes in mixed convection of air through a bottom heated inclined rectangular direct were investigated experimentally. The local spanwise-averaged heat transfer coefficient and air temperature variations with time at selected locations were measured and the cross plane secondary flow was visualized for the Reynolds number ranging from 35 to 186, Grashof number up to 5 X 10(6), and -20 degrees less than or equal to phi less than or equal to 26 degrees. The results indicated that the heat transfer enhancement is due to the presence of the buoyancy-driven secondary vortex flow and/or reverse flow. The onset of thermal instability was found to move upstream for a larger negative inclined angle (opposing convection) and/or a higher Grashof number and to be delayed for a larger positive inclined angle (aiding convection) and/or a higher Reynolds number. At increasing Grashof number, the instantaneous flow visualizations clearly showed the changes of the vortex flow and/or reverse flow structures in the downstream section of the duct. At slightly supercritical Grashof numbers the secondary flow is in the form of two pairs of longitudinal rolls with the vortex flow ascending along the side walls. For higher Grashof numbers the vortex rolls rotate in the opposite direction with the secondary flow descending near the side walls and the flow was found to be time periodic. At even higher Grashof numbers in opposing convection the buoyancy induced reverse flow exists and the flow is quasi-periodic. Further raising the Grashof number or lowering the Reynolds number causes the flow to change from a transitional quasi-periodic state to a chaotic turbulent stale.
High quality quantum dots fabricated by molecular beam epitaxy
(1996-02-01)
Lee, CP
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Liu, DC
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Damage free quantum dots have been fabricated directly using molecular beam epitaxy. Excellent photoluminescence has been obtained and is attributed to the absence of the non-radiative recombination centers and the enhanced oscillator strength for exciton recombination due to the confinement of quantum dots. The size variation of the quantum dots has been estimated from the width of the emission peak of low temperature photoluminescence (PL). A variation of only +/- 10 Angstrom is obtained. The existence of the quantum dots has also been verified directly from the image of the dots using atomic force microscopy. The image sizes of the quantum dots agree with that estimated from the PL blue shift.
A multi-granularity locking model for concurrency control in object-oriented database systems
(1996-02-01)
Lee, SY
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Liou, RL
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資訊科學與工程研究所
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Institute of Computer Science and Engineering
A locking model adopting a multi-granularity approach is proposed for concurrency control in object-oriented database systems. The model is motivated by a desire to provide high concurrency and low locking overhead in accessing objects. Locking in schemas and locking in instances are developed separately and then are integrated. Schema changes and composite objects are also taken into account. A dual queue scheme for efficient scheduling of lock requests is developed. The model consists of a rich set of lock modes, a compatibility matrix, and a locking protocol. Characteristic query examples on single class, class lattice, and composite objects are used to illustrate the comparison between the ORION model and the proposed model. It is shown that our locking model has indeed made some improvements and is suitable for concurrency control in object-oriented databases.
Suppression of the boron penetration induced dielectric degradation by using a stacked-amorphous-silicon film as the gate structure for pMOSFET
(1996-02-01)
Wu, SL
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Lee, CL
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Lei, TF
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電控工程研究所
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Institute of Electrical and Control Engineering
This work proposes a stacked-amorphous-silicon (SAS) film as the gate structure of the p(+) poly-Si gate pMOSFET to suppress boron penetration into the thin gate oxide, Due to the stacked structure, a large amount of boron and fluorine piled up at the stacked-Si layer boundaries and at the poly-Si/SiO2 interface during the annealing process, thus the penetration of boron and fluorine into the thin gate oxide is greatly reduced, Although the grain size of the SAS film is smaller than that of the as deposited polysilicon (ADP) film, the boron penetration can be suppressed even when the annealing temperature is higher than 950 degrees C, In addition, the mobile ion contamination can be significantly reduced by using this SAS gate structure, This results in the SAS gate capacitor having a smaller flat-band voltage shift, a less charge trapping and interface state generation rate, and a larger charge-to-breakdown than the ADP gate capacitor, Also the Si/SiO2 interface of the p(+) SAS gate capacitor is much smoother than that of the p(+) SAS gate capacitor.
Double graded-gap hydrogenated amorphous silicon carbide thin-film light-emitting diode with composition-graded N layer and carbon-increasing P layer
(1996-02-01)
Chen, YA
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Chen, JK
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Tsay, WC
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Laih, LH
;
Hong, JW
An hydrogenated amorphous silicon carbide (a-SiC:H) p-i-n thin-film light-emitting diode (TFLED), in which a composition-graded n layer and carbon-increasing p layer respectively replace the constant optical-gap p-a-SiC:H layer and n-a-SiC:H layer employed in the previously reported double graded-gap (DG) TFLED and which contains dopant-graded p-i and i-n junctions, was successfully fabricated tu improve the electroluminescence (EL) of TFLED. This device had a brightness of 400 cd/m(2) at an injection current density of 600 mA/cm(2) and its EL threshold voltage (V-th) was only 9.0 V. The device EL spectrum showed a peak at 586 nm wavelength and emitted yellowish-orange light. The proposed TFLED had good stability of EL intensity and the EL spectrum during normal operation. The optimum conditions of rapid thermal annealing (RTA), which improved the ohmic contact between the amorphous layer and external electrode of the device, were 5 min at 300 degrees C in a 250 Torr H-2 ambient.
Characterization of thin textured tunnel oxide prepared by thermal oxidation of thin polysilicon film on silicon
(1996-02-01)
Wu, SL
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Chiao, DM
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Lee, CL
;
Lei, TF
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電子工程學系及電子研究所
In this paper, the characteristics of thin textured tunnel oxide prepared by thermal oxidation of thin polysilicon film on Si substrate (TOPS) are studied, Because of the rapid diffusion of oxygen through the grain boundaries of the thin polysilicon film into the Si substrate and the enhanced oxidation rate at the grain boundaries, the oxidation rate of the TOPS sample is close to that of a normal oxide grown on a (111) Si substrate, Also, a textured Si/SiO2 interface is obtained, The textured Si/SiO2 interface results in localized high fields and causes a much higher electron injection rate, The optimum TOPS sample can be obtained by properly oxidizing the stacked alpha-Si film, independent of the substrate doping level, Also, the optimum TOPS sample exhibits a smaller electron trapping rate and a lower interface state generation rate when compared to the sample from a standard tunnel oxide process, These differences are attributed to a lower bulk electric field and a smaller injection area in the TOPS samples.
Comparison of two ambient beta gauge PM(10) samplers
(1996-02-01)
Tsai, CJ
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Cheng, YH
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交大名義發表
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環境工程研究所
;
National Chiao Tung University
This paper reports on the performance of the Kimoto 180 sampler and the Wedding ambient PM(10) beta gauge sampler. Monodisperse ammonium fluorescein test particles were generated in the laboratory and used to determine the penetration curve of the Kimoto 180 cyclonic inlet. It was found that the actual D-pa50 of the Kimoto 180 inlet, 3.5 mu m, is much lower than the designated standard value, 10 mu m. In the field test, the two beta gauge samplers were collocated with an Andersen SA 1200 high-volume sampler to compare their measured daily average PM(10) concentrations. The low D-pa50 of the Kimoto 180 inlet serves to explain why its daily average PM(10) concentrations were much lower than the actual PM(10) concentrations found in the field study. In addition, the PM(10) concentrations of the Kimoto 180 beta gauge sampler were found to be seriously affected by the water vapor content of the ambient air. In contrast, the daily average PM(10) concentrations of the Wedding beta gauge sampler were found to be more accurate, and influences by ambient conditions were insignificant.