Browsing by Author "Chen, TM"

Now showing 1 - 20 of 44

A new high-performance CMOS GHZ power amplifier design with common-mode signal cancellation technique
(2002)
Wu, CY
;
Wang, WC
;
Chen, TM
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work describes a novel common-made signal rejection method for power amplifiers. A power amplifier with standard 1P5M 0.25mum CMOS technology was simulated and analyzed. This common-mode signal cancellation method makes the performance, in terms of output power and efficiency of the power amplifier, more immune to input common-mode signals than conventional power amplifiers. Simulated results indicate that this fully balanced differential power amplifier yields 24dBm output power at 2.45GHz, from a 3.3V power supply. The simulated drain efficiency is 33.21%, and the overall power-added efficiency is 32.84%. The power amplifier is highly linear.
A study on the high-pressure synthesis and properties of praseodymium-substituted R(2)Ba(4)Cu(7)O(14+delta) (R=Nd, Eu, Tm) cuprates
(1996-04-01)
Kao, FS
;
Chen, TM
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The formation of phases in the (R(1-x)Pr(x))(2)Ba4Cu7O?(14+delta (R = Nd, Eu, Tm; Pr-doped R247 phases) system with x = 0 - 0.5 was investigated. Samples of the above three series were synthesized at 980 degrees C at 25 bar O-2, followed by annealing at 300 degrees C under 130 bar O-2 for 30 hours. Oxygen content of the samples has been determined by iodometric titration. X-ray diffraction indicated that nearly single-phased samples were obtained with err < 0.4, 0.5 and 0.5 for R = Nd, Eu and Tm, respectively, and the cell dimension of the Pr-doped R247 phases was found to expand steadily with increasing Pr content. Field-cooled temperature-dependent magnetization measurements showed that T-c of the Pr-doped R247 decreased with increasing Pr content. We have compared the dT(c)/dx for the three series with R = Nd, Eu and Tm with that for R = Y as a function of size of R(3+) ions and the results are discussed. In addition, the field-dependent magnetization studies at 5 K for a series of (Eu1-xPrx)(2)Ba4Cu7O14+delta samples with x = 0, 0.2, and 0.4 are also reported.
A study on the luminescent properties of new green-emitting terbium-activated CaIn2O4 : xTb phosphors
(2002-03-01)
Kao, FS
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
Calcium indate phosphors have been prepared by solid-state reactions at 1400 degreesC. This indate matrix permits photoluminescence when doped with terbium. It was found that under ultraviolet excitation with a wavelength of 254nm the phosphors revealed yellowish green luminescence that was attributed to the transitions from D-5(4) excited state to F-7(J) multiplet ground states of Tb3+ ions. The powder X-ray diffraction, photoluminescence spectra, brightness, fluorescence decay lifetime, and chromatic characteristics of the Tb3+-activated CaIn2O4 phosphors were systematically investigated and reported. (C) 2002 Elsevier Science B.V. All rights reserved.
A study on the luminescent properties of praseodymium-activated CaIn2O4 phosphors
(2000-12-01)
Kao, FS
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The photoluminescent (PL) properties and decay lifetime of a series of unprecedented praseodymium-activated calcium indates (CaIn2O4:xPr(3+)) have been investigated. The CaIn2O4:xPr(3+) (x = 6.25 x 10(-4), 0.5%, 1%, and 2%) was found to exhibit orange emission under ultraviolet excitation. With different levels of Pr3+ doping, the X-ray diffraction profiles, photoluminescence spectra and fluorescence decay lifetime as a function of Pr3+ concentration, and chromatic characteristics of CaIn2O4:xPr(3+) with different x's have been systematically investigated. The analysis of PL emission and excitation spectra, decay lifetime, and comparison of chromaticity coordinates and hues for CaIn2O4:xPr(3+) are presented and their implications are discussed. (C) 2000 Academic Press.
A study on the luminescent properties of red-emitting praseodymium-activated SrIn2O4 phosphors
(2001-01-01)
Kao, FS
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The photoluminescent (PL) properties of new red-emitting praseodymium-activated strontium indates have been investigated. A series of SrIn2O4:xPr(3+) (x = 6.25 x 10(-4), 0,5%, 2%, and 4%) phases were synthesized and found to exhibit red emission. With different levels of Pr3+ doping, the absolute brightness, CIE chromatic characteristics, PL and cathodoluminescence spectra, and luminescence decay lifetime (tau (R)) for SrIn2O4:xPr(3+) have been systematically investigated. The results are reported and their implications are discussed. (C) 2001 Academic Press.
Axial flow cyclone for segregation and collection of ultrafine particles: Theoretical and experimental study
(2005-03-01)
Hsu, YD
;
Chein, HM
;
Chen, TM
;
Tsai, CJ
;
環境工程研究所
In this study, an axial flow cyclone was designed, fabricated, and evaluated at different conditions of air flow rates (Q(0)) and low-pressure environments (P), especially for the segregation and collection of ultrafine particles. An evaporation/condensation type of aerosol generation system consisting of tube furnace and mixing chamber was employed to produce test aerosols. The test aerosol was then classified by a differential mobility analyzer (DMA) and number concentration was measured by a condensation nuclei counter (CNC) and an electrometer upstream and downstream of the cyclone, respectively. The s-shaped curve of the collection efficiency in submicron particle size range was obtained to be similar to the traditional cyclone found in the literatures when the particles were largerthan 40 nm at Q(0) = 1.07, 0.455 L(STP)/min, and P= 4.8-500 Torr. The curve was found to be fitted very well by a serniempirical equation described in this paper. Forparticles smaller than 40 nm, however, the collection efficiency was unusually increased as the particle diameter was decreased due to the fact that the diffusion deposition becomes the dominant collection mechanism in the low pressure conditions. A model composed of centrifugal force and diffusion deposition is presented and used to fit the experimental data. The cyclone was demonstrated to separate and collect ultrafine particles effectively in the tested vacuum conditions.
Design and fabrication of a photosensing nanodevice structure with CdSe and Au nanoparticles on a silicon chip
(2006-05-01)
Tu, CC
;
Li, YK
;
Chen, TM
;
Wu, CY
;
應用化學系
A newly developed tour-layered photosensing nanodevice was fabricated by integrating nanoparticles (NPs) on a silicon substrate. Through ionic interaction, negatively charged An NPs (similar to 15 nm) were assembled in alternate layers with positively charged CdSe NPs (similar to 5 nm) on the silicon oxide surface between the two Al electrodes. The silicon oxide surface after each step of the fabrication process was observed and evaluated by images obtained from the scanning electron microscope. By applying voltage biases across the electrodes, the currents were measured in the dark and under illumination using a 375-nm laser. It was found that a constant photocurrent increment can be obtained for different voltage biases, and the nanodevice structure with a longer length had less conductivity but a larger increment of photocurrent after illumination. In addition, the efficiency rate of photocurrent generation is much higher in comparison to that obtained from CdSe thin film. The fabrication process integrated a newly developed model of a diode-resistor array of semiconductor-metal junctions between CdSe and An NPs (nano-Schottky-diode structures), which can successfully explain the measured results. While nanotechnology has unprecedented advantages over the traditional silicon electronics, its technology presents physical challenges. However, the success of the fabrication of the multilayered photosensing nanodevice directly on the silicon chip paves the way for further applications and research.
Dielectric and electrical properties of SrTiO(3+/-y)-(SiO2)(x) thin films
(2005-07-21)
Chou, HY
;
Chen, TM
;
Tseng, TY
;
應用化學系
;
電子工程學系及電子研究所
110 nm thick SrTiO(3 +/- y)-(SiO2), thin films with x = 0-0.45 were prepared on Pt/Ti/SiO2/Si substrates using the chemical solution deposition method and then annealed at temperatures ranging from 600 degrees C to 900 degrees C for I min. The dielectric and electrical properties of the SrTiO(3 +/- y)-(SiO2)(x) were obviously affected by the annealing temperature and composition. The dielectric constant of the thin films increased with increasing annealing temperature and decreased with an increase in Si content while the leakage current density decreased with an increase in Si content. The 700 degrees C annealed SrTiO(3 +/- y)-(SiO2)(x) thin film with x = 0.25 has a suitable cm(-2). dielectric constant of 94.8 and a low leakage current of 1.27 x 10(-8) A The time-dependent dielectric breakdown curve of the 700 degrees C and 800 degrees C annealed SrTiO(3 +/- y)-(SiO2), films with x = 0.25 have an expected lifetime of over 10 years at electric fields higher than 0.6 MV cm(-1).
Direct observation of long-term durability of superconductivity in YBa2Cu3O7-Ag2O composites
(2003-10-01)
Lin, JJ
;
Lin, YH
;
Huang, SM
;
Lee, TC
;
Chen, TM
We report direct observation of long-term durability of superconductivity of several YBa2Cu3O7-Ag2O composites that were first prepared and studied almost fourteen years ago [J. J. Lin et al.: Jpn. J. Appl. Phys. 29 (1990) 497]. Remeasurements performed recently on both resistances and magnetizations indicate a sharp critical transition temperature at 91 K. We also find that such long-term environmental stability of high-temperature superconductivity can only be achieved in YBa2Cu3O7 with Ag2O addition, but not with pure Ag addition.
Effect of host compositions on the afterglow properties of phosphorescent strontium aluminate phosphors derived from the sol-gel method
(2001-05-01)
Chen, IC
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The effect of compositions of host precursors on the afterglow and phosphorescent decay properties of Eu2+- and Dy3+-coactivated strontium aluminates (SAED) synthesized by a sol-gel process has been investigated. A variety of strontium aluminates such as Sr3Al2O6, SrAl2O4, and SrAl12O19 have been identified in the samples prepared from starting precursors with Al/Sr ratios ranging from 1 to 12, respectively. The initial afterglow intensity (I-0) for SAED phases was found to vary with Al/Sr ratio of the sol-gel precursor, with a maximal I-0 appearing in the sample with Al/Sr of 2 in which SrAl2O4 dominated. The afterglow decay rate was found to be fastest for sample with Al/Sr ratio of 1:1 in which Sr3Al2O6 phase dominated. Moreover, the afterglow decay rates for those with Al/Sr ratio of 2:1 to 12:1, in which SrAl2O4 and SrAl12O19 dominated, were found to be slow and similar.
Effect of target materials on crystalline carbon nitride film preparation by ion beam sputtering
(1999-08-01)
Kuo, CT
;
Chen, LC
;
Chen, KH
;
Chen, TM
;
Lu, TR
In order to provide abundant chemical information, two novel bio-molecular target materials, instead of the conventional graphite target, were successfully developed to determine the possible formation mechanisms of carbon nitride during ion beam deposition. The azaadenine and adenine targets consist of carbonitro bonding, high N/C ratio as well as a six-fold carbonitro ring structure similar to that in hypothetical C3N4. Mass spectroscopy was used to determine the possible mechanisms of these two target materials. A lower electron beam energy at 75 eV was adopted to generate as abundant fragmental ions during the decomposition of these targets. Mass spectroscopy study on these two different targets indicates that the adenine target exhibits a more complex decomposition mechanism than the azaadenine target. However, the seven common hydrogenated carbonitro-species may suggest the same predominant mechanism during the decomposition of these two targets under the present deposition condition. The good correlation is one reason why two different targets can make almost the same quality crystalline carbon nitride films, including bonding, composition and structure. (C) 1999 Elsevier Science S.A. All rights reserved.
Electrical and dielectric properties of low-temperature crystallized Sr0.8Bi2.6Ta2O9+x thin films on Ir/SiO2/Si substrates
(2003-12-20)
Chou, HY
;
Chen, TM
;
Tseng, TY
;
應用化學系
;
電子工程學系及電子研究所
Ferroelectric thin films of bismuth layer structured compounds, Sr0.8Bi2.6Ta2O9+x (SBT) were deposited onto Ir/SiO2/Si substrates using metal organic decomposition (MOD) method. The crystallization of the SBT thin films annealed at various temperatures was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The polarization (P) versus electric field (E) characteristics exhibited a systematic variation from linear to non-linear polarization (hysteresis) with an increase in the annealing temperature of the SBT films. The leakage current density and dielectric constant of the SBT films were also strongly dependent on the annealing temperature, which in turn determined the grain size, mean surface roughness and inter diffusion through interfacial layers. The lowest leakage current density of 10(-9) A cm(-2) at 100 kV cm(-1) was obtained for SBT thin film annealed at 450 degreesC. The SBT thin films annealed at 650 and 700 degreesC remained fatigue-free up to 10 switching cycles. (C) 2003 Elsevier B.V. All rights reserved.
Electrochemiluminescence studies of the cyclometalated iridium(III) complexes with substituted 2-phenylbenzothiazole ligands
(2004-08-01)
Kapturkiewicz, A
;
Chen, TM
;
Laskar, IR
;
Nowacki, J
;
應用化學系
Electrogenerated chemiluminescence (ECL) studies have been performed for the iridium(III) cyclometalated L2Ir(acac) complexes with substituted 2-phenylbenzothiazole ligand L. Electron transfer (ET) generation of the excited (3)*L2Ir(acac) has been studied using a triple-potential-step technique in acetonitrile-dioxane (1:1) solutions containing 0.1 M (n-C4H9)(4)NPF6 as the supporting electrolyte. ET reactions between electrochemically generated L2Ir(acac)(+) and A(-) (radical anions of aromatic nitriles) species lead to very efficient generation of ECL emission. Extremely high ECL efficiencies (up to 0.40) close to the excited (3)*L2Ir(acac) luminescence yields have been found. (C) 2004 Elsevier B.V. All rights reserved.
Enhanced phosphorescence and electroluminescence in triplet emitters by doping gold into cadmium selenide/zinc sulfide nanoparticles
(2005-10-01)
Liu, HW
;
Laskar, IR
;
Huang, CP
;
Cheng, JA
;
Cheng, SS
Gold-cadmium selenide/zinc sulfide (Au-CdSe/ZnS) nanocomposites (NCs) were synthesized and characterized by transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, ultraviolet-visible (UV-visible) absorption and photoluminescence (PL) emission spectroscopy. The PL intensity in the Au-CdSe/ZnS NCs system was found to be much greater than that of CdSe/ZnS nanoparticles (NPs) alone, because of the surface-enhanced Raman scattering of An NPs. Adding Au-CdSe/ZnS NCs to the cyclometalated iridium(Ill) complex (Ir-complex) greatly enhanced the PL intensity of a triplet emitter. Three double-layered electroluminescence (EL) devices were fabricated where the emitting zone contains the definite mixture of Ir-complex and the NCs [molar concentration of Ir-complex/NCs = 1:0 (Blank, D-1), 1: 1 (D-2) and 1:3 (D-3)] and the device D-2 exhibited optimal EL performances. (c) 2005 Elsevier B.V. All rights reserved.
High purity nano-crystalline carbon nitride films prepared at ambient temperature by ion beam sputtering
(1999-07-18)
Lu, TR
;
Kuo, CT
;
Yang, JR
;
Chen, LC
;
Chen, KH
High purity nano-crystalline carbon nitride films have been successfully deposited by ion beam sputtering. A novel biomolecular C-N compound, 6-aminopurine, of which the characteristic features include covalent C-N bonding, high N/C ratio and a six-membered ring structure similar to that in the hypothetical C3N4 crystal, has been employed as the target material. The films can be deposited onto a variety of substrate, such as copper, silver, stainless steel, nickel and silicon wafer at ambient temperature. SAM examination indicates a high nitrogen-to-carbon ratio at about 0.51. XPS, IR and Raman studies reveal that the chemical bonding structures consist mainly of sp(3)-hybridized carbon as well as sp(2)-hybridized nitrogen and carbon. Both TEM and SAM mapping investigations indicate that the film contains a very dense and homogenous distribution of nanocrystalline grains. However, the structures of these crystals are yet to be determined since their TEM diffraction patterns only matched partially with the calculated pattern for beta-C3N4. (C) 1999 Elsevier Science S.A. All rights reserved.
High-pressure synthesis and characterization of rare-earth substituted (Y,R)(2)Ba4Cu7O15-delta (R = La, Tb, Yb, Lu) cuprates
(1998-04-01)
Chen, TM
;
Lee, SY
;
Ho, JS
;
應用化學系
;
Department of Applied Chemistry
In an attempt to investigate the formation of unknown R2Ba4Cu7O15-delta (R247; R = La, Tb, Yb, Lu) phases, we have prepared and characterized four series of (Y1-xRx)(2)Ba4Cu7O15-delta (R-doped Y247; R = La, Tb, Yb, Lu) cuprates. The substitution limit of R for Y was determined to be <: 10%, 50%, < 20% and 30% for phases with R = La, Yb, Tb and Lu, respectively, as indicated by x-ray diffraction (XRD) patterns. The lattice parameters for R-doped Y247 (R = Yb, Lu) phases were found to decrease with increasing R content due to the smaller size of R3+ compared to that of Y3+. With increasing content of R's the superconducting transition temperature (T-c) were found to first increase and then decrease from 77.1 K of pristine Y247, whereas the width of superconducting transition (Delta T-c) was found to increase with increasing dopant R content. The oxygen contents of R-doped Y247 phases have been experimentally determined by iodometric titration and were found to vary in a small range. Furthermore, a series of (Y0.9R0.1)(2)Ba4Cu7O15-delta (R = Y, Nd, Gd, Yb, Lu) phases were also synthesized and the effect of R3+ substitution on T-c was also investigated. With 10% of R3+ substitution T-c of R-doped Y247 phases was discovered to decrease with increasing ionic radii of R3+ and the corresponding oxygen composition was found to be essentially unchanged.
High-pressure synthesis and characterization of some Ca-doped R2Ba4Cu7O15-delta (R = Y, Sm, Dy) cuprate superconductors
(1998-04-01)
Chen, TM
;
Yarng, SL
;
Lin, JP
;
應用化學系
;
Department of Applied Chemistry
Three series of (R1-xCax)(2)Ba4Cu7O15-delta (Ca-doped R247; R = Y, Sm, Dy) cuprate superconductors have been synthesized at, 990 degrees C and under 26 - 30 bar of oxygen pressure. The effect of Ca2+ doping oil the variation of oxygen content, structural chemistry and superconductivity for Ca-doped R247 phases was investigated. The upper limit of substitution of Ca2+ for R in R247 was determined to be 0.10, 0.10, and 0.04, for phases with R = Y, Dy, and Sm, respectively, as indicated by x-ray diffraction (XRD) data. The lattice parameters of Ca-doped R247 phases were found to vary insignificantly or decrease: slightly upon Ca doping and these observations were attributed to the possibility of dual substitution of Ca2+ for both R3+ and Ba2+ sites. However, the corresponding orthorhombicity was found to increase or vary insignificantly. Upon Ca2+ doping the superconducting transition temperature (T-c) of R247 phases was found to decrease or increase from 93.8 K, 83.4 K and 64.5 K to 90.3 K (x = 0.10), 86.8 K (x = 0.10), and 72.2 K (x = 0.04) for phases with R = Y, Dy! Sm, respectively. Oxygen content or hole concentration (n(h)) of Ca-doped R247 phases was found to decrease with increasing Ca2+ content, as indicated by the iodometric titration data. The variation of T-c, sites of substitution and oxygen compositions for the title Ca-doped R247 phases will be discussed.
Highly efficient orange-emitting OLEDs based on phosphorescent platinum(II) complexes
(2005-06-02)
Laskar, IR
;
Hsu, SF
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The syntheses, characterisations, photophysical properties and their applications in organic light emitting devices of a series of 2-phenylbenzothiazolato (bt)/substituted 2-phenylbenzothiazolato (X-bt) platinum(II) based square-planar complexes [(X-bt)Pt(acac); acac = acetylacetonate; X = unsubstituted (1), F (2), OMe (3) and CF3 (4)] are discussed. Reaction of K2PtCl4 with btH/X-btH in glacial acetic acid for a few days results in the dinuclear chloro-bridged Pt(II) complex, (bt/X-bt)Pt(mu-Cl)Pt(bt/X-bt) which is cleaved with acetylacetone to give the corresponding mononuclear (bt/X-bt)Pt(acac) complex. The (MeO-bt)Pt(acac) complex has been characterized by X-ray single crystal structure analysis. The packing diagram shows the Pt-Pt distances and the intermolecular spacings are 3.369 and 3.360 angstrom, respectively, which is consistent with excimer formation. It has also been supported by time-resolved photoluminescence (PL) measurements. The nature of the lowest emitting states are the triplet MLCT as well as triplet pi-pi* states and it has been tuned according to the electronic properties of the substituents. The electroluminescent (EL) devices were fabricated by doping platinum complexes 1 and 2 (the corresponding devices denoted as D-1 and D-2, respectively) into the host CBP (4,4'(N,N'-dicarbazole)biphenyl), in the emitting zone with a doping content of 5%, 7% and 9%. The EL performances for these devices are exceptionally high (14.3 and 16.0 cd A(-1) @2 mA cm(-2) and luminances 10 550 and 11320 cd m(-2) @100mA cm(-2) for D-1 and D-2, respectively). (C) 2005 Elsevier Ltd. All rights reserved.
Inorganic acid emission factors of semiconductor manufacturing processes
(2004-02-01)
Chein, HM
;
Chen, TM
;
Aggarwal, SG
;
Tsai, CJ
;
Huang, CC
A huge amount of inorganic acids can be produced and emitted with waste gases from integrated circuit manufacturing processes such as cleaning and etching. Emission of inorganic acids from selected semiconductor factories was measured in this study. The sampling of the inorganic acids was based on the porous metal denuders, and samples were then analyzed by ion chromatography. The amount of chemical usage was adopted from the data that were reported to the Environmental Protection Bureau in Hsin-chu County according to the Taiwan Environmental Protection Agency regulation. The emission factor is defined as the emission rate (kg/month) divided by the amount of chemical usage (L/month). Emission factors of three inorganic acids (i.e., hydrofluoric acid [HF], hydrochloric acid [HCl], and sulfuric acid [H2SO4]) were estimated by the same method. The emission factors of HF and HCl were determined to be 0.0075 kg/L (coefficient of variation [CV] = 60.7%, n = 80) and 0.0096 kg/L (CV = 68.2%, n = 91), respectively. Linear regression equations are proposed to fit the data with correlation coefficient square (R-2) = 0.82 and 0.9, respectively. The emission factor of H2SO4, which is in the droplet form, was determined to be 0.0016 kg/L (CV = 99.2%, n = 107), and its R-2 was 0.84. The emission profiles of gaseous inorganic acids show that HF is the dominant chemical in most of the fabricators.
Investigating photoluminescence and electroluminescence of iridium(III)-based blue-emitting phosphors
(2006-03-27)
Laskar, IR
;
Hsu, SF
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The syntheses of two new cyclometalated ligands [2-(2',4'-difluorophenyl)-4-tert-butylpyridine (F(2)(t)Buppy) and 2-(2',4'-difluorophenyl)-4-oxyhexylpyridine (F(2)HexOppy)] were carried out. Blue-light emitting iridium(III) complex dopants [Ir(F(2)Buppy)(2)(acac/pic)] (acac = acetylacetone; pic = picolinic acid) and [Ir(F(2)HeXOppy)(2)(acac/pic)] were prepared using these cyclometalated ligands with acetylacetone and picolinic acid as their ancillary ligands. The structure of the complexes, [Ir(F(2)(t)Buppy)(2)(acac)] and [Ir(F(2)(t)Buppy)(2)(pic)] were authenticated by X-ray single-crystal structure analysis and showed an octahedral geometry. Comparative absorption and emission spectra of thin-films as well as their solution samples were studied. The variation of the lowest emitting states to their corresponding unsubstituted complexes, [Ir(F(2)ppy)(2)(acac/pic)] was also discussed. The electroluminescent (EL) device was fabricated using [Ir(F(2)(t)Buppy)(2)(pic)] as the dopant (D-I) into the emitting layer and compared with two other EL devices where [Ir(F(2)MeOppy)(2)(acac)] (D-II) and FIrpic (D-III) dopants were used in the same device structure. The lower driving voltages obtained for D-I with respect to D-II and D-III devices were rationalized. The exceptional lowering of the luminance yield of the substituted dopants containing devices, D-I and D-II, to that of D-III which contains the unsubstituted dopant was also investigated. (c) 2005 Elsevier Ltd. All rights reserved.