bluuebunny/crossref_metadata_2025 huggingface dataset:
Epitaxial Growth of BaTiO3 Thin Films by High Gas Pressure Sputtering
Authors: Yasumoto Takaaki , Yanase Naoko , Abe Kazuhide , Kawakubo Takashi
Published: October 2002

Heteroepitaxial BaTiO3 thin films with lattice-misfit strain were prepared on SrRuO3/SrTiO3 substrates by rf magnetron sputtering under high gas pressure, in order to realize large area deposi-tion with uniform ferroelectric properties. Lattice constants, composition and ferroelectric properties of the epitaxial BaTiO3 films were characterized as a function of pressure as well as the incident angle of sputtered particles, under the assumption that the sputtered particles were eradiated from the eroded area of the target surface. Although ferroelectric properties of films sputtered under low gas pressure had remarkable place dependability, they have been drastically improved by high gas pressure sputtering. X-ray diffraction analyses revealed that the BaTiO3 film deposited with a pressure of 6.3 Pa had a large lattice strain of 5%, even though the substrate was placed at a position directly facing the erosion area of the target, where a number of high-energy ions such as oxygen ions are thought to collide against the film surface if the pressure is low. The BaTiO3 film exhibited a ferroelectric hysteresis loop with remnant polarization of 43 µC/cm2. These results indicate that high gas pressure sputtering is effective for achieving large area uniformity of ferroelectric properties in heteroepitaxial BaTiO3 thin films.
Preparation and Ferroelectric Properties of Ti-Site Substituted BaTiO3 Thin Films
Authors: Kakemoto Hirofumi , Kakimoto Ken-ichi , Fujita Shigetaka , Masuda Yoichiro
Published: October 2002

Thin films of BaTi0.91(Hf0.5, Zr0.5)0.09O3 on Pt/SiO2/Si(100), Nb-doped SrTiO3 (100) and (111) substrates were synthesized by a pulsed laser deposition method using fourth harmonic generated light of Nd3+:YAG laser beam under low O2 partial pressure. The in-situ observation of BaTi0.91(Hf0.5, Zr0.5)0.09O3 film deposition on a Nb-doped SrTiO3 (100) substrate was performed using reflection high energy electron beam diffraction. The BaTi0.91(Hf0.5, Zr0.5)0.09O3 films deposited on Nb-doped SrTiO3 (100) and (111) substrates showed preferential [100] and [111] orientations, respectively. The ferroelectric properties of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin films were investigated by electrical measurements. The frequency dependence of the dielectric constant of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin film was influenced by low dielectric phase, and it was analyzed by the Debye model. The remanent polarization and coercive field of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin film were measured at room temperature, and those values were 7.4 µC/cm2 and 123 kV/cm, respectively.
Fabrication of PbTiO3/Pt/Yttria Stabilized ZrO2 Heteroepitaxial Films on Si Substrate
Authors: Tokita Kouji , Hoshi Hideo
Published: October 2002

Fabrication of PbTiO3/Pt/yttria-stabilized ZrO2(YSZ) heteroepitaxial films on Si substrate was investigated with the aim of applying them to electric devices such as integrated infrared sensors and ferroelectric random-access memories (FRAMs). First, a (100)YSZ buffer layer was epitaxially grown on a (100)Si substrate using reactive electron-beam evaporation. In this process, a metallic Zr film was deposited before YSZ deposition in order to prevent a Si substrate surface from oxidizing. Then, Pt film was sputtered on the buffer layer. A rough YSZ surface attained by slightly etching the Si substrate surface is found to be essential to obtain (100)-oriented Pt films, while (111)-oriented Pt films were obtained on a smooth YSZ surface. This indicates that we can control the orientation of Pt film by controlling the morphology of the YSZ surface. Lastly, a (001)-oriented PbTiO3 film was epitaxially grown on (100)Pt/(100)YSZ/(100)Si using metalorganic chemical vapor deposition (MOCVD).
Preparation of Pb(Zr, Ti)O3 Thin Films on Glass Substrates
Authors: Hioki Tsuyoshi , Akiyama Masahiko , Ueda Tomomasa , Onozuka Yutaka , Hara Yujiro , Suzuki Kouji
Published: October 2002

Lead-zirconate-titanate (PZT) thin films were prepared on non-alkaline glass substrates widely used in liquid crystal display (LCD) devices, by plasma-assisted magnetron RF sputtering with an immersed coil. After preparation of the PZT thin film, the glass was available for use in LCD device processing. No mutual diffusion of the elements was recognized between the glass substrate and the bottom electrode. The PZT layer had a dense film structure with rectangular and columnar grains, and only its perovskite phase was crystalline. PZT thin films on a glass substrate had leakage current densities of about 10-8 A/cm2, acceptable hysteresis loop shapes with the remanent polarization (P

r
) of 45 µC/cm2 and the coercive field (E

c
) of 90 kV/cm. Ferroelectric properties on a glass substrate almost conform with those on a Si-based substrate.
Ferroelectric and Colossal Magnetoresistive Properties of a PbZr1-xTixO3/La1-xSrxMnO3 Heterostructure Film
Authors: Mitsugi Fumiaki , Yamagata Yukihiko , Ikegami Tomoaki , Ebihara Kenji , Narayan Jagdish , Grishin Alexander M.
Published: October 2002

We report the ferroelectric and magnetoresistive properties and crystallization of a PbZr0.52Ti0.48O3 (PZT)/La0.8Sr0.2MnO3 (LSMO) heterostructure film prepared by pulsed-laser deposition on a MgO(100) single crystal substrate. Ferroelectric properties such as the hysteresis loop and dielectric constant of the Au/PZT/LSMO capacitor were compared with those of the Au/PZT/YBa2Cu3O7-x
(YBCO) superconductor heterostructure film. The resistivity of the LSMO film was as low as that of the YBCO film at room temperature. The fabricated Au/PZT/LSMO capacitor had a remanent polarization of 29 µC/cm2, a coercive field of 30 kV/cm and a dielectric constant of about 1000.
Low-Temperature Processing of Pb(Zr0.53,Ti0.43)O3 Thin Films by Sol-Gel Casting
Authors: Tomoya Ohno Tomoya Ohno , Masahumi Kunieda Masahumi Kunieda , Hisao Suzuki Hisao Suzuki , Takashi Hayashi Takashi Hayashi
Published: October 2002

This paper focuses on a new class of processing for the low-temperature deposition of relatively thick films. We propose a new process of sol-gel casting which involves the dispersion of fine crystalline particles in a sol-gel derived precursor solution followed by casting and annealing at relatively low temperatures. In this study, we describe the basic concepts for optimizing the process parameters. As a result, dense ferroelectric PZT(Pb(Zr0.53,Ti0.43)O3) films with thickness up to 9 µm were deposited by up to six coating operations (1.5 µm/one coating operation). The PZT thick film deposited under optimized process parameters exhibited relatively good ferroelectricity (remanent polarization of 12 µC/cm2 and coercive field of 12 kV/cm) and a good dielectric property (relative permittivity of about 1400).
Preparation and Evaluation of Pb(Zr, Ti)O3 Thin Films for Low Voltage Operation
Authors: Soyama Nobuyuki , Maki Kazunari , Mori Satoru , Ogi Katsumi
Published: October 2002

Pb(Zr, Ti)O3 (PZT) thin films with thickness of 120 nm were prepared on Pt/SiO2/Si substrate by using two types of sol–gel solutions. The film from modified solution consisted of uniform and small grain of perovskite phase, whereas the film from conventional solution consisted of large grain of perovskite phase and secondary phase. The film from modified solution had higher nucleation density for crystallization. That was why the different morphology between those two films occurred. The P-E hysteresis of the film from modified solution was well saturated at low applied voltage. P
r and E
c of the PZT(40/60) were 29.1 µC/cm2 and 58.3 kV/cm, respectively. This modified PZT sol–gel solutions enable to get thinner films, down to 120 nm, without degradation of the morphology and the properties.
Influence of La0.5Sr0.5CoO3 Heterostructure Electrodes on Pb(Zr,Ti)O3 Thin Film Properties
Authors: Vin Im Ki , Jin Kuh Bong , Oh Park Soon , In Lee Sang , Kil Choo Woong
Published: October 2002

The effect of multiple-layer bottom electrodes including a La0.5Sr0.5CoO3 (LSCO) layer on the ferroelectric and electric fatigue properties of the PbZr0.5Ti0.5O3 (PZT 50/50) thin film capacitor was investigated. Conductive LSCO thin films consisting of fine perovskite grains can be obtained at relatively low temperatures (400°C) by magnetron sputtering of the ceramic LSCO target. It is found that PZT capacitors having heterostructure electrodes such as Pt/PZT/LSCO/SiO2/Si and Pt/PZT/LSCO/Pt/Ti/SiO2/Si exhibit asymmetric hysteresis loops. These asymmetric capacitors also show fairly good fatigue endurance. Dependence of fatigue on the applied voltage will also be described.
Preparation and Characterization of Epitaxial Lead Zirconate Titanate Films on Pt/(Ti, Al)N/TiN/Si Substrates by Metalorganic Chemical Vapor Deposition
Authors: Sakurai Atsushi , Li Xio Min , Shiratsuyu Kohsuke , Tanaka Katsuhiko , Sakabe Yukio
Published: October 2002

[001]-Oriented lead zirconate titanate (PZT) thin films were epitaxially grown on Pt/titanium-aluminum-nitride (TAN)/titanium-nitride (TiN)/Si substrates by metalorganic chemical vapor deposition (MOCVD). Epitaxial thin films of TAN were formed as buffer layers on the Si substrates by pulsed-laser deposition (PLD) using TiN seed layers. Oxidation of the TAN was prevented by a sufficiently thick epitaxial Pt layer between the PZT and the TAN, thereby improving the crystallinity and electrical properties of the PZT films. The epitaxial PZT films had a dielectric constant of 697 and a remanent polarization of 38 µC/cm2.
Observations of Island Structures at the Initial Growth Stage of PbZrxTi1-xO3 Thin Films Prepared by Metalorganic Chemical Vapor Deposition
Authors: Fujisawa Hironori , Morimoto Koji , Shimizu Masaru , Niu Hirohiko , Honda Koichiro , Ohtani Seigen
Published: October 2002

Island structures of PbZr
x
Ti1-x
O3(PZT) (x=0.26 and 0.74) were observed prior to formation of a continuous film at the initial growth stage on a Pt(111)/SiO2/Si substrate by metalorganic chemical vapor deposition (MOCVD). Triangular-shaped (111)-oriented PZT islands were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Transmission electron microscopy (TEM) observations revealed that PZT islands 80 to 100 nm wide and 20 to 30 nm high had a twin structure due to the presence of tetragonal or rhombohedral structures. Hence, small PZT islands could have spontaneous polarization. In piezoresponse measurements using scanning probe microscopy (SPM), the phase difference between the vibrational signal of the SPM cantilever and the applied ac voltage changed from 0 to 180°, resulting in a hysteresis loop due to polarization reversal by a dc bias voltage. From this piezoresponse result, it was found that PZT islands had ferroelectricity.
Characterization of Metal-Ferroelectric-(Metal-)Insulator-Semiconductor (MF(M)IS) Structures Using (Pb, La)(Zr, Ti)O3 and Y2O3 Films
Authors: Tokumitsu Eisuke , Takahashi Daisuke , Ishiwara Hiroshi
Published: October 2002

Metal-ferroelectric-(metal-)insulator-semiconductor (MF(M)IS) structures are fabricated and characterized using (Pb, La)(Zr0.3Ti0.7)O3 (PLZT) and Y2O3 films. Y2O3 buffer layers are epitaxially grown on Si(111) substrates by molecular beam epitaxy and ferroelectric PLZT films are formed on (Pt/)Y2O3/Si by the sol-gel technique. It was found that the Al/Y2O3/Si MIS structure has a low leakage current of less than 10-8 A/cm2. The capacitance–voltage (C–V) characteristics of the PLZT/Y2O3/Si MFIS structure exhibit a hysteresis loop due to the ferroelectricity of the PLZT film with a memory window of 1 V. On the other hand, the memory window of the Pt/PLZT/Pt/Y2O3/Si MFMIS structures is significantly improved.
Preparation of SrBi2Ta1.5Nb0.5O9 Ferroelectric Thin Films by RF Sputtering on Large Substrate
Authors: Masuda Takeshi , Miyaguchi Yusuke , Suu Koukou , Sun Shan
Published: October 2002

Ferroelectric SrBi2(Ta, Nb)2O9(SBTN) thin films were prepared by RF magnetron sputtering utilizing a multichamber production tool (ULVAC CERAUS ZX1000). Accurate and dynamic compositional control provided by this method results in excellent ferroelectric performances such as large P
r up to 15 µC/cm2, at least 109 cycles fatigue free and good 6-inch wafer uniformity. Good process reproducibility was also confirmed in terms of deposition rate, composition, and electrical properties through a 30-wafer nonstop sputtering test. These results indicate that the SBTN sputtering process is promising for ferroelectric memory production.
Effects of Crystallization Annealing Sequence for SrBi2Ta2O9 (SBT) Film on Pt/SBT Interface Morphology and Electrical Properties of Ferroelectric Capacitor
Authors: Yang Woo Seok , Yeom Seung Jin , Kim Nam Kyeong , Kweon Soon Yong , Roh Jae Sung
Published: October 2002

SrBi2Ta2O9 (SBT) film was crystallized to form fine grains and a smooth surface by rapid thermal annealing (RTA), but form large grains and a rough surface by main furnace annealing. The sequence of furnace annealing was changed to improve the morphology of the Pt/SBT interface and the leakage property of a Pt/SBT/Pt capacitor. For the conventional sequence of furnace annealing before top electrode deposition, the capacitor showed a good switching polarization (P*-P∧) of 17 µC/cm2 but a high short fail rate of 56% due to the rough Pt/SBT interface. However, using the new sequence of furnace annealing after top electrode deposition on RTA-treated SBT film, a very smooth Pt/SBT interface and a resultant low short fail rate of 7% was obtained, but the value of P*-P∧ was decreased to 14 µC/cm2 due to a restrained grain growth of the SBT film under Pt top electrode.
Phase Formations and Electrical Properties of (SrxBa1-x)Bi2Ta2O9 Thin Films
Authors: Lee Won-Jae , You In-Kyu , Yang Il-Suk , Yu Byoung-Gon , Cho Kyoung-Ik
Published: October 2002

The phase formation and electrical properties of (Sr
x
Ba1-x
)Bi2Ta2O9 (SBBT) thin films prepared by the metal-organic decomposition method on Pt/Ti/SiO2/Si substrates have been investigated. It was observed that the microstructure and electrical properties of SBBT thin films dramatically varied with the Ba content. While the remanent polarization and dielectric constant decreased with increasing Ba content in SBBT thin films, the insulating properties significantly improved. The SBBT films also exhibited good fatigue characteristics under bipolar stressing to 1010 cycles.
Metal-Organic Chemical Vapor Deposition and Characterization of Strontium Bismuth Tantalate (SBT) Thin Films
Authors: Burgess Darren , Schienle Frank , Lindner Johannes , Schumacher Marcus , Juergensen Holger , Solayappan Narayan , McMillan Larry , Paz de Araujo Carlos , Uchiyama Kiyoshi , Otsuki Tatsuo
Published: October 2002

The metal-organic chemical vapor deposition (MOCVD) of ferroelectric thin films is being widely investigated for the manufacture of devices requiring a high density of volatile or non-volatile memory which goes beyond the limits of current mass production techniques. One of the more important challenges in the MOCVD of multi-component oxide thin films is the precise control of stoichiometry which relates directly to the films' electrical characteristics. A novel approach to liquid precursor delivery embodied in the AIXTRON TriJetTM liquid delivery system is reported. Physical and electrical properties of thin films as well as deposition characteristics as a function of various process parameters are described in detail. Most notably 2P
r=13 µC/cm2 at 5 V with leakage current density J
l=1E-8 A/cm2 @≤5 V were obtained. In addition, films with excellent thickness uniformity with 3σ=2.25% at 180 nm were deposited on 6′′ Pt/TiO
x
/Si wafers. Finally, near 100% step coverage with a maximum 2:1 aspect ratio (0.5 µm) was achieved.
Method of Distinguishing SrBi2Ta2O9 Phase from Fluorite Phase Using X-Ray Diffraction Reciprocal Space Mapping
Authors: Saito Keisuke , Mitsuya Masatoshi , Nukaga Norimasa , Yamaji Isao , Akai Takao , Funakubo Hiroshi
Published: October 2002

In the Sr–Bi–Ta–Nb–O system, three crystallographic phases are known to exist: the SrBi2(Ta1-x
Nb
x
)O9 (SBTN) perovskite, fluorite and pyrochlore phases. It is considered that the fluorite phase is a low-temperature phase of SBT, which tends to grow in excess bismuth compositions, and the pyrochlore phase tends to grow in bismuth-deficient compositions. In conventional X-ray diffraction (XRD) characterization, the SBTN phase shows strong (115) diffraction around 29 [2θ deg]. Unfortunately, however, the other two phases also show their (111) and (222) diffractions near the same angle when the film is prepared on a platinum-coated silicon substrate. Therefore, the phase identification of the SBTN phase from the other two phases is almost impossible by the conventional technique. We employed XRD reciprocal space mapping to distinguish these phases in the present study. The three crystallographic phases were identified and distinguished from each other. It is ascertained that this technique is effective to identify crystallographic phases especially in the case in which more than two phases show similar diffraction angles.
Low-Temperature Preparation of SrBi2Ta2O9 Thin Films by Electron Cyclotron Resonance Plasma-Enhanced Metalorganic Chemical Vapor Deposition and Their Electrical Properties
Authors: Nukaga Norimasa , Mitsuya Masatoshi , Funakubo Hiroshi
Published: October 2002

A SrBi2Ta2O9 (SBT) thin film was prepared by electron cyclotron resonance plasma-enhanced metalorganic chemical vapor deposition (ECR-MOCVD). The deposition temperature dependence of the composition of the film was lesser than that of films prepared by conventional thermal MOCVD. An almost single phase of SBT was obtained at 610°C. The crystallinity of this film was higher than that of the film prepared by thermal MOCVD at 500°C and subsequent heat treatment at 800°C. The leakage current density of this film was small, on the order of 10-8 A/cm2 up to 240 kV/cm. Moreover, two fold the remanent polarization and the coercive field at an applied electric field of 400 kV/cm were 14.5 µC/cm2 and 77 kV/cm, respectively. These values were larger than those of the film prepared by thermal MOCVD at 500°C with heat treatment at 800°C.
Josephson Switching Device Utilizing the Quantum Transitions in a Superconducting Quantum Interference Device Loop
Authors: Yoshinao Mizugaki Yoshinao Mizugaki , Kei Saito Kei Saito , Aleksander Ignace Braginski Aleksander Ignace Braginski , Tsutomu Yamashita Tsutomu Yamashita
Published: October 2002

We propose a new type of Josephson switching device which utilizes quantum transitions in a superconducting quantum interference device (SQUID) loop. This device is driven by a DC bias current and RF magnetic field. The output voltage is determined by the transition rate and the AC-Josephson relationship. We investigate the desirable device parameters by simulation. Two parameters, the maximum step height and the overlapped current region for the 0th and 1st steps, are plotted as functions of frequency and power of the RF-field activation. We also derive the relationship between the gain and device parameters. The analytical relationship is in good agreement with the numerical results. Besides the simple switching operation, a flip-flop operation is also successfully simulated. The results indicate that the device with appropriate parameters is suitable for switching applications.
Ferroelectric Sr2(Nb, Ta)2O7 Thin Films Prepared by Chemical Solution Deposition
Authors: Kim Chang Young , Koo Chang Young , Woo Dong Chan , Lee Hee Young
Published: October 2002

Ferroelectric Sr2(Nb, Ta)2O7 (SNTO) thin films were prepared by chemical solution deposition process, i.e. the modified sol-gel method. The stock solutions were spin-coated onto either Pt/Ti/SiO2/Si(100) or Pt/TiO2/SiO2/Si(100) substrate. After multiple coating/baking steps, dried thin film stacks were annealed for crystallization at 850–1000°C in oxygen. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses revealed that the crystallization temperature by modified sol-gel process can be lowered to 850°C if Pt/TiO2/SiO2/Si(100) substrate was used, while temperature higher than 950°C is required for Pt/Ti/SiO2/Si(100) substrate. Leakage current and relative permittivity (ε
r) values were measured in the range of about 10-9–10-7 A/cm2, and 30–45, respectively, depending on the composition, heat-treatment and substrate type. Polarization hysteresis loops were not saturated regardless of composition and annealing temperature. Remanent polarization (2P
r) and coercive field (E
c) values for typical SNTO(30/70) film were approximately 1.9 µC/cm2, and 17 kV/cm, respectively, when ±5 V pulse was applied.
Initial Stage of Film Growth of Pulsed Laser Deposited YMnO3
Authors: Ito Daisuke , Fujimura Norifumi , Ito Taichiro
Published: October 2002

To improve the polarization-electric field (P–E) characteristic of pulsed laser deposited YMnO3 film, the initial stage of the film growth was studied. We confirmed that an yttrium-rich layer with poor crystallinity was formed at the initial stage of film growth, and this resulted in the large orientation distribution of the films. Stoichiometric YMnO3 films without an yttrium-rich layer were successfully obtained by optimizing the laser power density, oxygen gas pressure, and use of ozone gas. Eventually, the P–E characteristic of the YMnO3 film was improved.
Internal Friction and Dielectric Measurements in Lead Zirconate Titanate Ferroelectric Ceramics
Authors: Bourim El Mostafa , Tanaka Hidehiko , Gabbay Maurice , Fantozzi Gilbert
Published: October 2002

Elastic modulus (Young's modulus M and shear modulus G) and internal friction Q
-1 are measured as a function of temperature from -180°C to 500°C in undoped lead zirconate titanate (PZT) ferroelectric ceramics in the range of kHz and low frequencies (0.1 to 1 Hz). New phase transition temperatures at the morphotropic zone at low temperatures are determined from the elastic modulus minimum. Permittivity ε and dielectric loss tan
(δ) are measured in the frequency range of 20 Hz to 10 kHz. Both mechanical and electrical measurements allow the observation of relaxation peaks in the ferroelectric phase. The Arrhenius plots of all these results show that it is possible to investigate these relaxation processes using both experimental techniques.
Dielectric, Pyroelectric and Piezoelectric Properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 Ceramics Modified with Ag2O
Authors: Bae Kim Gang , Won Choi Seong
Published: October 2002

Dielectric, pyroelectric and piezoelectric properties of
0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3
ceramics modified with Ag2O have been investigated. The dielectric constant and
loss were determined for ceramic samples. The pyroelectric coefficient and
spontaneous polarization were measured by the static Byer-Roundy method
as a function of temperature.
The addition of Ag2O had negligible effect on the level of diffuseness of the phase transition.
The dielectric and
pyroelectric peak temperatures shifted slightly to lower temperature with the
addition of Ag2O.
Dielectric, pyroelectric and piezoelectric
properties of the base composition were improved with the addition of small amounts
of Ag2O.
High-Performance PbZn1/3Sb2/3O3–PbNi1/2Te1/2O3–PbZrO3–PbTiO3 Ceramics Sintered at a Low Temperature with the Aid of Complex Additives Li2CO3–Bi2O3–CdCO3
Authors: Wang Xiaoxing , Murakami Kenji , Kaneko Shoji
Published: October 2002

Low-temperature-sintered PbZn1/3Sb2/3O3–PbNi1/2Te1/2O3–PbZrO3–PbTiO3 (PZS–PNT–PZT) ceramics with high piezoelectric properties were prepared from commercially available materials using complex additives of Li2CO3–Bi2O3–CdCO3 (LBC) as a sintering aid. The introduction of LBC complex additives in PZS–PNT–PZT ceramics can not only lower the optimum sintering temperature from 1265°C to 980°C, but can also improve the electromechanical properties. The results of the isothermal shrinkage kinetics and Scanning Electron Microscopy (SEM) observations suggest that the sintering of PZS–PNT–PZT ceramics with the addition of LBC additives seems to be mainly facilitated by the occurrence of a liquid phase during heating. The rate of grain growth is related to the densification stages.
Structural and Dielectric Studies of the Phase Transitions in Pb(Yb1/2Ta1/2)O3-PbTiO3 Ceramics
Authors: Byung Park Soon , Kil Choo Woong
Published: October 2002

A dielectric phase diagram of the pseudobinary (1-x)Pb(Yb1/2Ta1/2)O3-xPbTiO3 solid solution system was determined. The crystal structures and the dielectric properties were investigated in terms of the PbTiO3 concentration. As the PbTiO3 concentration increases, the crystal structure changes from monoclinic to pseudocubic and then to tetragonal. A morphotropic phase boundary that separates the pseudocubic phase from the tetragonal phase has been determined at x ≈0.5. The phase transition of pure Pb(Yb1/2Ta1/2)O3 is unusual in that it undergoes a paraelectric-antiferroelectric transition at 310°C and another secondary antiferroelectric-ferroelectric transition at about 177°C. This successive phase transition characteristic confers a rather unique feature on the (1-x)Pb(Yb1/2Ta1/2)O3-xPbTiO3 phase diagram.
Unidirectionally Textured CaBi4Ti4O15 Ceramics by the Reactive Templated Grain Growth with an Extrusion
Authors: Takeuchi Tsuguto , Tani Toshihiko , Saito Yasuyoshi
Published: October 2002

Dense CaBi4Ti4O15 (CBT) ceramics with a unique texture were prepared by the reactive templated grain growth (RTGG) method using an extrusion technique. Plate-like Bi4Ti3O12 (BIT) particles, a reactive template for CBT, were mixed with other oxide and carbonate powders and unidirectionally aligned by extrusion. During sintering, oriented CBT grains were formed in situ topotaxially on the oriented BIT particles, and the templated grain growth and their densification eventually fabricated textured CBT ceramics. X-ray diffraction measurements and scanning electron microscopic observations revealed that the plate-like CBT grains were unidirectionally oriented parallel to the extruding direction without uniaxial alignment. Textured CBT ceramics poled in the extruding direction exhibited electromechanical coupling coefficients (k
33) and piezoelectric coefficients (d
33 and g
33) more than two times as large as one of nontextured ceramics with the same composition.
Growth, Electric and Thermal Properties of Lead Scandium Niobate-Lead Magnesium Niobate-Lead Titanate Ternary Single Crystals
Authors: Hosono Yasuharu , Harada Kouichi , Yamashita Yohachi , Dong Ming , Ye Zuo-Guang
Published: October 2002

Single crystals of the xPb(Sc1/2Nb1/2)O3–yPb(Mg1/3Nb2/3)O3–zPbTiO3 (PSMNT 100x/100y/100z) ternary system have successfully been grown by a flux method using 71.4 mol% PbO–28.6 mol% B2O3 flux. The crystals were grown in a platinum crucible by mass crystallization achieved by the slow cooling of a 50PbO:20B2O3:30PSMNT 29/34/37 (mol%) molten solution from 1,200°C to 880°C at 1.2°C/h. The resulting two types of crystals, 2–3 mm in length with perovskite structure and 5–7 mm in length with pyrochlore structure, coexist. Inductive charge plasma (ICP) chemical analysis revealed that the composition of the pulverized powder of perovskite crystal is PSMNT 43/17/40, which is slightly different from the charged composition of PSMNT 29/34/37. One of the single crystals near the morphotropic phase boundary (MPB) showed a dielectric constant peak of 200°C. The grown PSMNT crystals show good thermal stability of the perovskite phase with partical decomposition starting at 1128°C and peritectic melting at 1308°C.
Influence of Material Composition on 3rd Nonlinear Piezoelectric Coefficient in Lead Zirconate Titanate Ceramics
Authors: Ishii Keisuke , Murata Toshiro , Tashiro Shinjiro , Igarashi Hideji
Published: October 2002

The relationship between crystal structure and nonlinear piezoelectric coefficient was investigated in lead zirconate titanate-lead antimony niobate ceramics with various Zr/(Zr+Ti) ratios and MnO contents, using rectangular-bar-shaped samples. The electromechanical coupling factor k
31 and 3rd nonlinear piezoelectric coefficient ξ31 were measured near the resonance frequency of length-extensional 1/2 λ mode vibration. Among the ceramics having various Zr/(Zr+Ti) ratios, the minimum ξ31 was observed when the crystal structure of the sample was just on the morphotropic phase boundary, at which k
31 showed the maximum value. The ξ31 also decreased with the increase of MnO additive.
Thickness-Shear Vibration Mode Characteristics of SrBi4Ti4O15-Based Ceramics
Authors: Oka Hitoshi , Hirose Masakazu , Tsukada Takeo , Watanabe Yasuo , Nomura Takeshi
Published: October 2002

Dielectric and piezoelectric properties have been investigated in bismuth layer-structure compounds SrBi4Ti4O15 (SBT) and BaBi4Ti4O15 (BBT)-based solid solutions. Lanthanum-substituted and manganese-added SBT and BBT form solid solutions for all levels of Ba substitution. The Curie temperature and coercive field strength decrease monotonously with the amount of Ba substitution. The mechanical quality factor, Qm, of the thickness-shear vibration mode also decreases. The value of elastic compliance increases with the amount of Ba substitution, but conversely its temperature dependency decreases.
Temperature Dependence of Phonon Hole Position
Authors: Tsuruoka Fujio
Published: October 2002

The frequency where the phonon hole is detected in piezoelectric powder particles shows negative temperature dependence. When the temperature is decreased or increased from the temperature at which the hole was written into the piezoelectric powder, the half-height width of the hole becomes broader and the hole height decreases, and the hole finally becomes undetectable. Then as the temperature returns to the writing temperature, the hole recovers its form. These phenomena are explained as being due to the specimen particles not being uniform in size and/or the crystallographic angle and the hole being composed of many different modes of oscillation whose temperature dependences differ from each other.
Application of Multilayered Ceramic Capacitor to Pb-Free Electromechanical Transducer
Authors: Yoshiyuki Jyouno Yoshiyuki Jyouno , Yoshiro Tomikawa Yoshiro Tomikawa
Published: October 2002

Piezoelectric ceramic transducers are widely used in ultrasonic electronics. However, since many of them contain Pb, they are regarded to be undesirable from the viewpoint of environmental pollution. Therefore, Pb-free piezoelectric transducers are desired for practical applications. In this paper, we examine a Pb-free transducer. As the structure of the Pb-free transducer we use a multilayered ceramic capacitor because it consists of Pb-free materials. We expect that the multilayered ceramic capacitor will operate not only as an electrostrictive transducer, but also as a good electrostatic transducer because of its very thin layered construction and high dielectric constant. It has the following advantages: it does not contain Pb and does not need poling treatment, which is usually required by conventional piezoelectric ceramic transducers. The first part of this paper describes the operation principle of the new Pb-free transducer and in the second part, basic experiments are described.
First-principles Investigation of the Phase Stability for Ba(B1/3
′2+B2/3
′′5+)O3 Microwave Dielectrics with the Complex Perovskite Structure
Authors: Takahashi Takeshi
Published: October 2002

The phase stability of Ba(B1/3
′2+B2/3
′′5+)O3 microwave dielectrics with the complex perovskite structure has been investigated using first-principles calculations. Our calculations indicate that many Ba(B1/3
′2+B2/3
′′5+)O3 (B′2+=Co, Mg, Mn, Ni, Zn; B′′5+=Nb, Ta) compounds in equilibrium should be fully ordered in the 1:2 B-site structure with space group P3m1 (D3d
3). Our calculations disagree with the experimental result for Ba(Mn1/3Nb2/3)O3, but is consistent with many experimental obsernations for other Ba(B1/3
′2+B2/3
′′5+)O3 compositions. The correlation between order-disorder phenomena and several characteristics has also been discussed. We find that the greater the stability of the ordered 1:2 structure with respect to the disordered phase, the higher the experimentally measured microwave Q-factor. It is found that neither both ionic radius difference and electronegativity differences between the B′ and B′′ ions have any relationship to phase stability. Also, our results show that B-site cation ordering causes cell distortion and more stable phase of ordered structure can enhance cell distortion.
Microwave Dielectric Properties of Bi-Added Ba4Nd9+1/3Ti18O54 Solid Solutions
Authors: Okawa Takashi , Imaeda Masaki , Ohsato Hitoshi
Published: October 2002

We have investigated the formation and microwave dielectric properties of the tungstenbronze-type like solid solutions, that is, Bi ions dissolved in Ba6-3x
Nd8+2x
Ti18O54 solid solution with x=2/3. According to the increase of y in the Ba4(Nd1-y
Bi
y
)9+1/3Ti18O54 compositions, the change of the lattice parameters has an inflection point at y=0.05. Bi was substituted into A2 sites for Ba up to y=0.05 and into A1 sites for Nd over y=0.05. As y increased, the dielectric constant, ε

r
, increased and the quality factor, Q·f, decreased. The temperature coefficients of the resonant frequency, τ
f
, improved to 17 ppm/°C at y=0.15. The relationship between the lattice parameters and the microwave dielectric properties of the Bi-added Ba4Nd9+1/3Ti18O54 solid solutions is also presented.
Microwave Dielectric Characteristics of the Ca2/5Sm2/5TiO3-Li1/2Nd1/2TiO3 Ceramics
Authors: Kim Woo Sup , Yoon Ki Hyun , Kim Eung Soo
Published: October 2002

Microwave dielectric properties of the (1-x)Ca2/5Sm2/5TiO3-xLi1/2Nd1/2TiO3 ceramics were investigated in the range of 0.2 ≤x ≤0.8. The unloaded Q values and the temperature coefficients of the resonant frequency (TCF) of the specimens decreased with increasing Li1/2Nd1/2TiO3. Nearly zero TCF value composition with high dielectric constant was obtained at x=0.3. Dielectric constant increased with an increase of Li1/2Nd1/2TiO3, and showed a maximum value around x=0.6, and then decreased with further addition of Li1/2Nd1/2TiO3. The change in the dielectric constant of the specimens with the addition of Li1/2Nd1/2TiO3 could be explained by the intrinsic factor such as lattice anharmonicity, which was obtained from the far infrared reflectivity spectra in the range of 50 to 4000 cm-1.
Diameter Control of K3Li2-xNb5+xO15+2x Single-Crystal Fibers
Authors: Makoto Matsukura Makoto Matsukura , Junichi Murakami Junichi Murakami , Tomoaki Karaki Tomoaki Karaki , Masatoshi Adachi Masatoshi Adachi
Published: October 2002

Potassium lithium niobate, K3Li2-x
Nb5+x
O15+2x
(KLN) single-crystal fibers have been grown using the laser-heated pedestal growth (LHPG) technique. Ceramic source rods of K3.00Li1.70Nb5.30O15.6 (KLN53) and K3.00Li1.85Nb5.15O15.3 (KLN51.5) were adapted to grow the fibers with the same compositions. The diameter deviations at various growth rates were estimated. For the <110 > oriented KLN53 fibers, increase of the growth rate decreased the diameter deviation and the minimum root mean square diameter deviation was 1.8% when the growth rate was 66 mm/h. For the <110 > oriented KLN51.5 fibers, the minimum diameter deviation was 1.7% when the growth rate was 40 mm/h. From the dielectric properties along the grown fiber, the fiber without diameter deviation was determined to have homogeneous composition along the fiber. However, the Curie temperature measurements revealed that the composition of the KLN51.5 fiber did not coincide with that of the ceramic source rods.
Growth and Characterization of Silver Thiogallate (AgGaS2) Crystals by the Hydrothermal Method
Authors: Komatsu Ryuichi , Watanabe Noriko , Komai Eiji , Kitakaze Arashi , Ikeda Ko
Published: October 2002

A silver thiogallate (AgGaS2) crystal has been successfully grown by a hydrothermal method in order to avoid the occurrence of the exsolution texture in a grown crystal which leads to the lowering of the optical transparency in a wide range. The characterization of grown crystal is also investigated, and compared with the crystal grown by Bridgman method.
Semilinear Self-Pumped Phase-Conjugate Mirror Using Two Coupled Cu:(K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 Crystals
Authors: Doi Masato , Sasaki Akira , Iwata Futoshi , Zheng Yujin
Published: October 2002

A semilinear self-pumped phase-conjugate mirror was successfully formed using two crystals of copper doped (K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 (Cu:KNSBN). The self-pumped phase-conjugate mirror was formed simply by an incident Ar+ laser beam (λ=488 nm) similar to the conventional Cat type self-pumped phase-conjugate mirror. The phase-conjugate reflectivities were investigated as a function of the incident beam position and the incident beam angle. The acceptable conditions of the incident beam position and angle for the self-pumped phase-conjugate mirror were 2.6 and 1.5 times wider, respectively than those of the normal Cat type self-pumped phase-conjugate mirror.
Electron-Irradiation Induced Phase Transition in Poly (Vinylidene Fluoride-Trifluoroethylene) Copolymer
Authors: E. Cross Tomoaki Karaki
Published: October 2002

The electron-irradiation induced ferroelectric-to-relaxor phase transition in poly (vinylidene fluoride-trifluoroethylene) (P(VDF/TrFE)) copolymer was investigated. One polymer with a composition of 53 mol% VF2 (PVDF53) and a Curie temperature of 67°C, and another with 76 mol% VF2 (PVDF76) and a Curie temperature of 136°C, were used in the research. Changes in hysteresis loop, permittivity and electrostriction during the phase transition were measured. X-ray diffraction showed that PVDF53 had a second-order phase transition during the irradiation in which the structure was changing continuously, while PVDF76 had a first-order phase transition in which the structure changed discontinuously. Field-induced piezoelectric response was measured using a loudspeaker which provided a vibrational force, and d
31 = 135 pC/N at bias E
3 = 40 MV/m was obtained. The conditions for electron irradiation and composition of the copolymers were discussed.
Raman Studies of the Effects of Nb Dopant on the Ferroelectric Properties in Lead Titanate Thin Film
Authors: Desheng Fu Desheng Fu , Tomoya Ohno Tomoya Ohno , Takeshi Ogawa Takeshi Ogawa , Hisao Suzuki Hisao Suzuki , Kenji Ishikawa Kenji Ishikawa , Takashi Hayashi Takashi Hayashi
Published: October 2002

Raman spectroscopy was used to study the effects of Nb additives in ferroelectric lead titanate thin films. Raman spectra were measured from lead titanate thin films with Nb concentrations between 0 and 5%. The Nb additive was found to significantly influence the profile of the A1(2TO) mode, which is the relative vibration between the Ti atom and other atoms along the c-axis, indicating that the doped Nb occupied a Ti position. A decrease of all transverse modes followed the increase in Nb. The observed mode frequencies were used to extract the dependence on Nb addition of the clamped dielectric constants. The dielectric constants along both thea- andc-axes increase with increasing Nb concentration.
Crystal Structure of High-Temperature Paraelectric Phase in Bi-Layered Perovskite Sr0.85Bi2.1Ta2O9
Authors: Akira Onodera Akira Onodera , Takayuki Kubo Takayuki Kubo , Keiji Yoshio Keiji Yoshio , Seiji Kojima Seiji Kojima , Haruyasu Yamashita Haruyasu Yamashita , Toshihiko Takama Toshihiko Takama
Published: October 2002

The crystal structure of Bi-layered perovskite Sr0.85Bi2.1Ta2O9 was determined at 750 K by X-ray Rietveld analysis. Sr0.85Bi2.1Ta2O9 with space group A21am at room temperature transforms to the paraelectric phase above 670 K, passing through a probable intermediate state at 510 K. Assuming two possible orthorhombic Fmmm and tetragonal I4/mmm space groups, analysis of the crystal structure of the paraelectric phase gave the final discrepancy factors R

w
p
of 11.3% and 9.9%, respectively. Examination of possible reflections and peak positions at high-angles proved that the true space group is I4/mmm for the high temperature paraelectric phase. The lattice constants are a=3.927 (1), c=25.142 (1) Å at 750 K. The TaO6 octahedron is not perfect and is slightly distorted along the c-axis, having the dipole moment of 0.478 debye.
Dislocations Preferentially Generated in Compressed Regions of Saddle-Shaped Deformed, Precipitation-Softened, Czochralski-Grown Silicon Wafers
Authors: Shimizu Hirofumi
Published: October 2002

Distribution of dislocations in Czochralski-grown (CZ) silicon (Si) circular wafers thermally deformed in a saddle shape at 1273 K was investigated by using X-ray topography (for the bulk Si) and an etching technique (for the surface). In such deformed wafers softened by oxygen precipitation (density of oxide precipitates, including all secondary microdefects, was less than 2×1015 m-3), slip dislocations were preferentially generated and randomly distributed in the concave side (compressed region) of the wafer. This preference is due to the lattice mismatch between oxide precipitates and Si matrix, which causes internal stress that compresses the Si matrix and results in an externally applied stress to the concave side of the wafer. When the density of microdefects was less than 2×1013 m-3, slip dislocations were introduced along the <110> slip direction in a line from the top surface of the wafer to a neutral plane. At this density, dislocations were initiated at wafer surfaces where thermal stresses were the highest and then propagated into the neutral plane in both the concave and convex sides. Based on our results and on previous numerical analyses of the relationship between the critical stress required to multiply slip dislocations and the microdefect density, we developed a model that explains how slip dislocations multiply in saddle-shaped deformed wafers.
Atomic-Layer Epitaxy of Silicon on (100) Surface
Authors: Yasuo Satoh Yasuo Satoh , Keiji Ikeda Keiji Ikeda , Satoshi Sugahara Satoshi Sugahara , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Atomic-layer epitaxy (ALE) of Si on the (100) surface has been studied. The ALE temperature window for the (100) surface was as wide as that for the (111) surface, under optimum hydrogen pressure conditions. The grown film surface was smooth only within the upper half of the window. Surface roughness increased with ALE execution cycle, due to the combined dynamic effects of excess growth, etching and surface migration of adsorbates within an execution cycle, but took an extremely small value under a special set of ALE parameters.
Nucleation and Surface Roughness in Self-Limiting Monolayer Epitaxy of GaAs
Authors: Kono Kazushi , Kurabayashi Toru , Nishizawa Jun-ichi , Esashi Masayoshi
Published: October 2002

The surface morphology produced by molecular layer epitaxy (MLE) was investigated using atomic force microscopy (AFM). The surface morphology and roughness estimated quantitatively were not consistent with the temperature dependence of self-limiting growth. The degree of roughness had two states in the monolayer growth temperature range from 445 to 534°C. In the growth temperature region over 475°C, nucleated islands along [110] the direction one monolayer high were observed on the grown surface. When the growth temperature was less than 475°C, such nucleation did not occur and a smooth surface without islands was obtained with a roughness of less than one monolayer. To understand island formation, the nucleation and the islands at each growth cycle were investigated.
Effect of Charge Distribution in Quantum Dots Array on Two-Dimensional Electron Gas
Authors: Song Hai-Zhi , Lan Sheng , Akahane Kouichi , Jang Kee-Youn , Okada Yoshitaka , Kawabe Mitsuo
Published: October 2002

With InGaAs quantum dots (QDs) embedded in the vicinity, GaAs/AlGaAs two-dimensional electron gas (2DEG) was studied by transport measurements and by calculations with QDs charges as Coulomb scattering centers. The mobility of 2DEG decreases with increasing QDs density up to 5×1010 cm-2, which can be fitted by considering the finite spatial extension of QD-charge distribution. However, two distinct effects are observed as the QDs density increases from 5×1010 cm-2 to 2×1011 cm-2. One is that the 2DEG mobility is saturated at a low level, and the other is that it gradually approaches the high value of 2DEG without QDs. The former can be reproduced by taking into account the interdot overlapping of electron probability distributions, while the latter is argued to be the result of interdot coupling through wavefunction overlapping. These explanations are supported further by the temperature dependence of the conductance.
Inclusion of Strain Effect in Miscibility Gap Calculations for III–V Semiconductors
Authors: Schlenker Dietmar , Miyamoto Tomoyuki , Chen Zhibiao , Kawaguchi Masao , Kondo Takashi , Gouardes Eric , Gemmer Jochen , Gemmer Christian , Koyama Fumio , Iga Kenichi
Published: October 2002

A new and simple treatment of miscibility gap calculations for ternary and quaternary semiconductors including strain is presented. Our treatment leads to the same result as that of previous treatments, in the case of lattice-matched layers, but provides a more realistic and rigorous description for coherently strained layers. We also discuss the differences between our treatment and previous treatments, including misfit strain caused by the substrate. Our treatment is applied in miscibility gap calculations for GaInNAs and GaInAsSb material systems. Theoretical predictions by miscibility gap calculations are compared with growth experiments and show reasonable agreement.
Characterization and Reliability of Lightly-Doped-Drain Polysilicon Thin-Film Transistors with Oxide Sidewall Spacer Formed by One-Step Selective Liquid Phase Deposition
Authors: Shih Po-Sheng , Chang Ting-Chang , Huang Tiao-Yuan , Yeh Ching-Fa , Chang Chun-Yen
Published: October 2002

We have proposed and successfully demonstrated a novel process for fabricating a lightly doped drain (LDD) polysilicon thin-film transistor (poly-Si TFT). The oxide sidewall spacer in the new process is formed by a simple one-step selective liquid phase deposition (LPD) at 23°C. In contrast with conventional methods, this new process does not require an additional photolithographic step for defining the non-self-aligned offset gate, or the deposition of an oxide layer and subsequent etch-back to form the self-aligned sidewall spacer. Devices fabricated by the new process have a lower leakage current and a better ON/OFF current ratio, compared with non-LDD control devices. The new device also shows excellent current saturation characteristics at high bias and better has hot-carrier endurance. Since the apparatus used for LPD oxide deposition is simple and inexpensive, the new process appears to be promising for future high-performance poly-Si TFT fabrication.
Propagation Reactions and Structures of Hydrogenated Amorphous Silicon Depending on Plasma Sources with Different Excitation Frequencies
Authors: Azuma Masanobu , Shimizu Isamu
Published: October 2002

Chemical reactions related to Si-network formation and its structure using SiH
n
Cl
m
(n+m≦3) as the precursor decomposed by various plasma sources such as modulated radio frequency (RF), very high frequency (VHF) and electron cyclotron resonance (ECR) plasmas are investigated. The characteristics of each plasmas estimated by diagnostic study are systematically varied depending on the excitation frequency of the plasma source. We confirmed that atomic hydrogen is an effective agent to promote the propagation reaction of the Si network due to its strong reactivity under SiH
m
Cl
n
flow. We also report that high-quality hydrogenated amorphous silicon films with defect density as low as 2×1015 cm-3 are successfully fabricated by ECR hydrogen plasma at growth rates higher than 10 Å/s.