Browsing by Issue Date, starting with "1995-11-09"

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NOVEL MODEL OF 2/1 BALANCE-TO-UNBALANCE TRANSMISSION-LINE TRANSFORMER
(1995-11-09)
KUO, CC
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KUO, MY
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KUO, MS
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交大名義發表
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電控工程研究所
The modelling and simulation of 2:1 balance-to-unbalance transmission-line transformers (balun TLT) are presented. The validity of the complete equivalent model of the basic 2:1 balun is confirmed by the excellent match between the simulated results and experimental data. This complete model makes a contribution to predict and explain the characteristics of the 2:1 balun, including low-frequency and high frequency operation.
GENETIC-BASED FUZZY HIT-OR-MISS TEXTURE SPECTRUM FOR TEXTURE ANALYSIS
(1995-11-09)
LEE, YG
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LEE, JH
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HSUEH, YC
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交大名義發表
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資訊工程學系
A new method using a fuzzy hit-or-miss transform recognition procedure, which measures degrees of fit of specified patterns within an image, is proposed for texture analysis. For a given texture, three optimal texture patterns (structuring elements) dynamically generated by genetic algorithms are used to inspect the degrees of fit by using the fuzzy hit-or-miss transform, respectively. The distribution of these degrees of fit, converted into a texture spectrum, is used as the texture feature for texture analysis.
BORON INCORPORATION IN SI1-XGEX FILMS GROWN BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION USING SI2H6 AND GEH4
(1995-11-13)
CHEN, LP
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CHOU, CT
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HUANG, GW
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TSAI, WC
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CHANG, CY
0.1% B2H6 diluted in hydrogen is used as the p-type dopant gas in Si1-xGex grown by ultrahigh vacuum chemical vapor deposition (UHVCVD) using Si2H6 and GeH4. The boron concentration is evaluated by secondary ion mass spectrometry (SIMS). The boron concentration of Si1-xGex increases with the increase of the GeH4 flow rate, that is, Ge fraction, by keeping Si2H6 and B2H6 how rates constant. The result may be due to the increase of the vacant surface sites which is caused by the increase of the hydrogen desorption rate when a higher Ge fraction epilayer is grown. (C) 1995 American Institute of Physics.
EXISTENCE OF ALGEBRAIC MATRIX RICCATI-EQUATIONS ARISING IN TRANSPORT-THEORY
(1995-11-15)
JUANG, J
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交大名義發表
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應用數學系
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National Chiao Tung University
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Department of Applied Mathematics
We consider the existence of positive solutions of a certain class of algebraic matrix Riccati equations with two parameters, c (0 less than or equal to c less than or equal to 1) and alpha (0 less than or equal to alpha less than or equal to 1). Here c denotes the fraction of scattering per collision, and cu is an angular shift. Equations of this class are induced via invariant imbedding and the shifted Gauss-Legendre quadrature formula from a simple transport model. By establishing the existence of positive solutions of such equations, the problem of the convergence of some iterative schemes for solving them can be completely solved.
RATES OF THE REACTIONS CN+H2CO AND NCO+H2CO IN THE TEMPERATURE-RANGE 294-769 K
(1995-11-15)
CHANG, YW
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WANG, NS
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應用化學系
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Department of Applied Chemistry
The rate coefficients of the reactions: (1) CN + H2CO --> products, and (2) NCO + H2CO --> products in the temperature range 294-769 K have been determined by means of the laser photolysis-laser induced fluorescence technique. Our measurements show that reaction (1) is rapid: k(1)(294 K) = (1.64 +/- 0.25) x 10(-11) cm(3) molecule(-1) s(-1); the Arrhenius relation was determined as k(1) = (6.7 +/- 1.0) x 10(-11) exp[(-412 +/- 20)/T] cm(3) molecule(-1) s(-1). Reaction (2) is approximately a tenth as rapid as reaction (1) and the temperature dependence of k, does not conform to the Arrhenius form: k(2) = 4.62 x 10(-17)T(1.71) exp(198/T) cm(3) molecule(-1) s(-1). Our values are in reasonable agreement with the only reported measurement of k(1); the rate coefficients for reaction (2) have not been previously reported.
BANDGAP SHRINKAGE OF DEGENERATE P-TYPE GAAS BY PHOTOLUMINESCENCE SPECTROSCOPY
(1995-11-15)
FENG, MS
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FANG, CSA
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CHEN, HD
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材料科學與工程學系
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電控工程研究所
Photoluminescence characteristics of heavily carbon-, beryllium- and zinc-doped GaAs were studied in this investigation. The band-to-acceptor (e,A) transition was identified via various doping concentrations from 10(17) to 10(20) cm(-3) and the temperature from 20 to 300 K. As a result the (e,A) peak was found to be a dominant peak at 20 K instead of the band-to-band (B,B) peak at p> 1 x 10(19) cm(-3). The (e,A) peak was also observed at 300 K and enhanced with the increasing carrier concentration at p> 2.8 x 10(18) cm(-3). Bandgap shrinkage of these samples was qualitatively obtained. When p> 1 x 10(19) cm(-3), the impurity band merges with the valence band and the binding energy of the acceptor is equal to zero. Consequently, the bandgap can be taken as the energy between the conduction-band minimum and the top of the impurity band.
PTGE OHMIC CONTACT TO N-TYPE INP
(1995-11-15)
HUANG, WC
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LEI, TF
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LEE, CL
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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
A new ohmic contact system, Ge/Pt/Ge/Pt/n-InP, was studied systematically by measuring its specific contact resistance and by using Auger electron spectroscopy, x-ray-diffraction analysis, Rutherford backscattering spectroscopy, and scanning electron microscopy. It was found that the system has a wide temperature range for annealing, i.e., 450-550 degrees C, to achieve the specific contact resistance of the order of 1.0x10(-5) Omega cm(2). It can achieve a low specific contact resistance of 7.71x10(-6) Omega cm(2) when it is subjected to rapid thermal annealing at 500 degrees C for 30 s. The whole process is a solid phase reaction so that a smooth surface morphology is obtained. The ohmicity is due to the heavy doping of Ge in the regrown InP film. The contact system exhibits good thermal stability, being able to maintain a low specific contact resistance of 9.15X10(-6) Omega cm(2) for 20 h, 400 degrees C aging, and 2.77x10(-5) Omega cm(2) for 80 h aging. (C) 1995 American Institute of Physics.
THE NOVEL NONLINEAR DC RESPONSE OF AG THIN-FILMS DEPOSITED ON POROUS SILICON - A FRACTAL MODEL EXPLANATION
(1995-11-15)
YOUNG, TF
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KUO, WC
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JIANG, IM
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CHANG, TC
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CHANG, CY
We have observed a novel non-linear de resistivity of Ag thin films deposited on porous silicon (PS) surfaces. We also found that as the porous silicon is oxidized in a HNO3 solution, the de resistivities of the Ag thin films become two orders of magnitude smaller, and behave linearly but are divided into three different regions. Each region exhibits different resistivities which drops abruptly at the thresholds. The resistivity decreases as the current increasing into a higher current region. The atomic force microscopy (AFM) image shows a self-affine structure of the PS surface with wires, hillocks and voids on various scales. After oxidation, the rough surface is smoothed down to simpler fractal hillock clusters. The silver clusters are deposited on the glazed surface in a fractal-like size distribution. A branched Koch curve fractal model is proposed in this study to model the tunneling between fractal-like silver clusters. It explains the stepwise linear fractal-like resistivity behavior.
KINETICS OF POLYMERIZATION-INDUCED PHASE-SEPARATION
(1995-11-15)
CHEN, SH
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CHEN, WJ
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交大名義發表
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光電工程學系
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National Chiao Tung University
We have stud led a Monte Carlo computer simulation on a mo del for polymerization-induced phase separation. The time evolution of the structure factor are found to preserve the scaling law obtained from the thermally quenched phase separation, A novel peaking behavior of the mean cluster size of solvent molecules has been found and can be explained by the irreversibility of polymerization. The simulation results are in agreement with experimental observations.
NOVEL OXA-CAGE COMPOUNDS - SYNTHESIS, STRUCTURES, AND THE FORMATION MECHANISM OF TETRAACETAL OXA-CAGES AND CONVEX TETRAQUINANE OXA-CAGES
(1995-11-17)
WU, HJ
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LIN, CC
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交大名義發表
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應用化學系
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National Chiao Tung University
Several novel tetraacetal era-cage compounds 5a-d and convex tetraquinane era-cage compounds 16a-d and 17b-d are synthesized from alkylfurans in three steps. Ozonolysis of the cis-endo-1,4-diones 3a-d in dichloromethane at -78 degrees C followed by reduction with dimethyl sulfide gives the era-cages 5a-d in high yields, respectively. The structures of these new tetraacetal era-cages are deduced from their spectral data and proven for the first time by X-ray analysis of the crystalline compound 5a. Ozonolysis of 3a-d in dichloromethane at -78 degrees C followed by treatment with triethylamine gives the convex tetraquinane era-cages 16a-d and 17b-d in 85-90% yields, respectively. The structures of these novel convex tetraquinane era-cages are finally proven by X-ray analysis of the crystalline compound 16a. Two reaction mechanisms via the common final ozonides are proposed for the formation of these two different types of era-cage compounds. The structures of the final ozonides formed by ozonolysis of the norbornene derivatives 3 are deduced to be 9 with endo stereochemistry on the basis of their spectral data and the formation of these two types of era-cages from the final ozonides. In reaction with the final ozonides, triethylamine is found to act as a base instead of a reducing agent, a different function from that of dimethyl sulfide. The synthesis of era-cages 24 and 25, which possess aromatic substituents directly on the skeleton, has also been accomplished.
BALUN DESIGN FOR UNIPLANAR BROAD-BAND DOUBLE BALANCED MIXER
(1995-11-23)
CHIOU, HK
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CHANG, CY
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LIN, HH
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電信工程研究所
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Institute of Communications Engineering
A novel balun based on an asymmetric coplanar waveguide with finite ground plane (ASYCPWFGP) to coplanar strip (CPS) transition is presented. A return loss better than 16dB is obtained up to 50 GHz. The baluns are combined with four silicon Schottky barrier crossover diodes to yield a planar double-balanced mixer (DBM) which demonstrates an ultra-broadband performance up to 40 GHz.
Electrical properties of diamond films grown at low temperature
(1995-12-01)
Chen, CF
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Chen, SH
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Lin, KM
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交大名義發表
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材料科學與工程學系
The unique electronic properties of diamond, associated with the emergence of chemical vapour deposition (CVD) methods for the growth of thin films on non-diamond substrates, have led to considerable interest in electronic devices fabricated from this material. In our previous work, we found that polycrystalline diamond films can be deposited at 250 degrees C using CH4-CO2 gas mixtures. Studying the electrical properties and the upcoming problems of applications of low-temperature diamond films are relevant concerns. In this work, the electrical properties of diamond films grown at low temperatures were studied and compared with those of conventional diamond films. Platinum was used as the upper electrode. The resistivity of low-temperature diamond was around three orders of magnititude lower than that of conventional diamond. However, both the low temperature and conventional growth diamond exihibited rectifying behavior when platinum was used as the upper electrode.
Growth of SiC films on Si(100) by electron cyclotron resonance chemical vapor deposition using SiH4/CH4/H-2
(1995-12-01)
Liu, CC
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Lee, CP
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Cheng, KL
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Cheng, HC
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Yew, TR
SiC films were deposited on Si(100) substrates by electron cyclotron resonance chemical vapor deposition at 500 degrees C using SiH4/CH4/H-2 gas mixtures. The chemical composition and crystalline microstructure were investigated by x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy, respectively. The film composition and microstructure are correlated to process variables. The deposition mechanism which controls the film characteristics is presented.
Effect of nitrogen on diamond growth using unconventional gas mixtures
(1995-12-01)
Hong, TM
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Chen, SH
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Chiou, YS
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Chen, CF
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交大名義發表
The influence of nitrogen on the growth of diamond using unconventional gas mixtures of CH4-CO2 by microwave plasma chemical vapor deposition was investigated. A clear improvement in the surface morphology and quality of the diamond films indicates the beneficial effect of adding nitrogen to CH4-CO2 gas mixtures. However, most interestingly, for lower methane concentration, the addition of small amounts of nitrogen resulted in the formation of isolated diamond particles possessing a vacant ''cage-like'' structure with completed (100) facets. This result indicates that the continued addition of nitrogen gives rise to the deterioration of (111) facets and the retention of (100) facets. Analysis using Auger electron spectroscopy and secondary ion mass spectroscopy shows very low and uniform levels of nitrogen in the diamond films. Although the amount of atomic hydrogen in the ground state decreased and CN radicals increased with increasing amounts of added nitrogen, good-quality diamond films were deposited resulting from a larger amount of atomic oxygen and the decrease in the C-2 emissions in the gas phase under optimum conditions.
Fuzzy logic approach for removing noise
(1995-12-01)
Lee, YG
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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
This paper shows how fuzzy reasoning techniques can be applied on smoothing filters design. It uses the fuzzy concept to decide whether a pixel in an image is a noise one or not in order to achieve maximum noise reduction in uniform areas and preserve details as well.
STRUCTURAL EFFECT ON BAND-TRAP-BAND TUNNELING INDUCED DRAIN LEAKAGE IN N-MOSFETS
(1995-12-01)
WANG, TH
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CHANG, TE
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HUANG, CM
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YANG, JY
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CHANG, KM
The structural dependence of the hot carrier stress incurred drain leakage current via band-trap-band tunneling in off-state has been modeled and characterized in conventional S/D, DDD, and LDD n-MOSFET structures, The results shows that lateral field enhanced band-trap-band tunneling is primarily responsible for an increased drain leakage current after hot carrier stress in LDD structures while vertical field induced tunneling is dominant in conventional S/D and DDD structures.
CHARACTERISTICS OF TOP-GATE THIN-FILM TRANSISTORS FABRICATED ON NITROGEN-IMPLANTED POLYSILICON FILMS
(1995-12-01)
YANG, CK
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LEI, TF
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LEE, CL
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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
The electrical characteristics of top-gate thin-film transistors (TFT's) fabricated on the nitrogen-implanted polysilicon of the doses ranging from 2 x 10(12)-2 x 10(14) ions/cm(2) were investigated in this work, The experimental results showed that nitrogen implanted into polysilicon followed by an 850 degrees C 1 h annealing step had some passivation effect and this effect was much enhanced by a following H-2-plasma treatment. The threshold voltages, subthreshold swings, ON-OFF current ratios, and field effect mobilities of both n-channel and p-channel TFT's were all improved, Moreover, the hot-carrier reliability was also improved, A donor effect of the nitrogen in polysilicon was also found which affected the overall passivation effect on the p-channel TFT's.
A 2-PHASE ENCRYPTION SCHEME FOR ENHANCING DATABASE-SECURITY
(1995-12-01)
HWANG, MS
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YANG, WP
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資訊工程學系
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Department of Computer Science
In this article, we propose a two-phase encryption algorithm for data base systems. The system, a record-oriented cryptosystem, allows the encryption and decryption of fields within a record by means of writing and reading subkeys of fields. In addition, we develop two algorithms for cryptographic relational algebra in data base systems. Two simple methods of solving the key management problem in the subkey scheme are presented.
CHARACTERISTICS OF POLYCRYSTALLINE FILMS GROWN BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION SYSTEM
(1995-12-01)
LIN, HY
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LEI, TF
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LIN, HC
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CHANG, CY
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TWU, RC
In situ boron-doped polycrystalline Si1-xGex (poly-Si1-xGex) films deposited by ultrahigh vacuum chemical vapor deposition (UHV/CVD) system were characterized. Optimum fitted values of grain boundary trap state densities, 4.0 x 10(12) cm(-2) and 4.9 x 10(12) cm(-2) were obtained for poly-Si and poly-Si0.79Ge0.21, respectively. The extracted average carrier concentration in the grain agrees with secondary ion mass spectroscopy (SIMS) analysis. In turn, we found that these films are suitable Hall elements to sense magnetic field. Experimental results show that the sensitivity decreased with the increasing input current, which can be well explained using the thermionic emission theory. Finally, we use these films to fabricate thin film transistors.
Electrical characteristics and annealing study of boron-doped polycrystalline diamond films
(1995-12-01)
Chen, SH
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Chen, SL
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Tsai, MH
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Shyu, JJ
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Chen, CF
Annealing processes are an important area of fundamental research within the field of diamond electronic applications. In this study, annealing was applied to as-grown boron-doped diamond films. The current-voltage (I-V) characteristics of the Al/boron-doped diamond films were also investigated. First, the conductivity of films was examined to determine the effect of annealing on boron-doped diamond films. Experimental results indicated that the activation energy for the as-deposited diamond films (intrinsic or light boron-doped) is about 0.38 eV. After annealing, the activation energy did not change. However, the activation energy of the heavily doped films remarkably would change to 0.014 eV after annealing. Next, Fourier transform infrared spectroscopy (FTIR) and cathodoluminescence (CL) were performed to understand more clearly the correlation between the activation energy and the annealing effect on B-doped diamond films. These results revealed that for the lightly B-doped films, the boron atoms were effectively activated at the substitutional site. For the heavily doped case, boron was initially located in an inactive site (e.g., grain boundary, interstitial or clustering sites) and would diffuse into the substitutional site after 900 degrees C annealing.