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1 Feb 2008

Volume 103, Issue 3, Articles (03xxxx)

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J. Appl. Phys. 103, 031101 (2008); http://dx.doi.org/10.1063/1.2836410 (35 pages)

Ce-Wen Nan, M. I. Bichurin, Shuxiang Dong, D. Viehland, and G. Srinivasan
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Preparation and characterization of Eu-doped LiNbO3 films prepared by the sol-gel method

Makoto Takahashi, Kazuki Iyoda, Yoshihiko Maeda, Toshiyuki Miyauchi, Sadao Ohkido, Shoji Sato, Koichi Wakita, Naofumi Kajitani, Kazutoshi Hotta, and Masato Kurachi

J. Appl. Phys. 103, 034101 (2008); http://dx.doi.org/10.1063/1.2830718 (6 pages) | Cited 3 times

Online Publication Date: 1 February 2008

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Europium (Eu3+)-doped lithium niobate (LiNbO3) thick films were deposited on a z-cut congruent LiNbO3 (LN) substrate by the sol-gel method from 0.20 mol dm−3 precursor solution containing various Eu3+ concentrations and 0.10 mol dm−3 polyvinylalcohol, and their crystal characteristics were evaluated. The Eu3+ concentration in the LN film was controlled by the Eu3+ concentration in the starting solution. The orientation relationships between Eu3+-doped LN films and LN substrates were determined by x-ray diffraction and Raman spectroscopy, and (006) oriented Eu-doped LN epitaxial layers with parallel epitaxial relationships could be grown on the z-cut LN wafer. The refractive indices of Eu3+-doped LN films decreased with the increase of Eu3+ concentration. The luminescence intensities (5D0→7FJ emission) increased with increasing of the Eu3+ ion concentration.
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68.55.A- Nucleation and growth
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Ferroelectric and fatigue behavior of Pb(Zr0.52Ti0.48)O3/(Bi3.15Nd0.85)Ti3O12 bilayered thin films

C. H. Sim, Z. H. Zhou, X. S. Gao, H. P. Soon, and J. Wang

J. Appl. Phys. 103, 034102 (2008); http://dx.doi.org/10.1063/1.2838333 (9 pages) | Cited 10 times

Online Publication Date: 5 February 2008

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Bilayered ferroelectric thin films consisting of Pb(Zr0.52Ti0.48)O3 (PZT) and (Bi3.15Nd0.85)Ti3O12 (BNT) layers have been successfully fabricated via a synthesis route of combining sol-gel and rf sputtering. Both ferroelectric layers are well retained in both PZT/BNT and BNT/PZT bilayered films as suggested by x-ray diffraction and secondary ion mass spectroscopy analyses. Their ferroelectric and dielectric properties are largely dependent on the thicknesses of the constituent layers. An anomalous enhancement in polarization is demonstrated by the PZT/BNT bilayered thin film, whereby the switchable polarization increases dramatically upon >106 cycles of polarization switching. The fatigue anomaly observed for the PZT/BNT bilayered thin film is related to the space charges that are accumulated at the interfaces in the heterolayered structure. By comparison, the BNT/PZT bilayered thin film exhibited better ferroelectric behavior than that of the PZT/BNT film where the P-E hysteresis loops were relatively well saturated with higher polarization. The BNT/PZT bilayered thin film also demonstrated a much improvement in fatigue behavior as compared to that of the single layer PZT film.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization
77.22.Jp Dielectric breakdown and space-charge effects

Orientation-dependent multiferroic properties in Pb(Zr0.52Ti0.48)O3–CoFe2O4 nanocomposite thin films derived by a sol-gel processing

Hong-cai He, Jing Ma, Jing Wang, and Ce-Wen Nan

J. Appl. Phys. 103, 034103 (2008); http://dx.doi.org/10.1063/1.2838482 (5 pages) | Cited 20 times

Online Publication Date: 5 February 2008

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Bilayered multiferroic nanocomposite films of preferentially oriented Pb(Zr0.52Ti0.48)O3 (PZT) and CoFe2O4 (CFO) were prepared on general Pt/Ti/SiO2/Si substrate via a simple solution processing. Different annealing processings resulted in different preferential orientations for the PZT layers in the bilayered thin films, on which the dependence of properties, including ferroelectric, ferromagnetic, and magnetoelectric properties, in the PZT-CFO nanocomposite thin films was investigated. Strong ferroelectric and ferromagnetic responses and, in particular, direct magnetoelectric coupling effect were simultaneously observed in these bilayered thin films at room temperature.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
75.70.Ak Magnetic properties of monolayers and thin films
75.80.+q Magnetomechanical effects, magnetostriction
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Domain reversal properties and refractive index changes of magnesium doped lithium niobate upon ion exposure

L. Jentjens, H. Hattermann, K. Peithmann, M. Haaks, K. Maier, and M. Kösters

J. Appl. Phys. 103, 034104 (2008); http://dx.doi.org/10.1063/1.2838207 (5 pages) | Cited 5 times

Online Publication Date: 7 February 2008

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Irradiation of optical damage resistant, magnesium doped lithium niobate crystals with fast, high-energy 3He2+ ions changes important material properties. In the interaction region, where the ions transmit through the material, the ferroelectric coercive field EC is diminished from 6.0 kV mm−1 down to 5.0–5.4 kV mm−1 after transmission of 41 MeV 3He2+ particles. This enables easier domain reversal in irradiated crystals compared to untreated material. Besides, large changes of the refractive index of the crystals on the order of 6×10−3 are induced by the treatment. Moderate annealing treatments do not diminish Δn, but refresh the coercive field.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
61.82.Ms Insulators

Electrical, optical, and structural characteristics of Al2O3 thin films prepared by pulsed ultrasonic sprayed pyrolysis

S. Carmona-Tellez, J. Guzman-Mendoza, M. Aguilar-Frutis, G. Alarcon-Flores, M. Garcia-Hipolito, M. A. Canseco, and C. Falcony

J. Appl. Phys. 103, 034105 (2008); http://dx.doi.org/10.1063/1.2838467 (7 pages) | Cited 2 times

Online Publication Date: 7 February 2008

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The optical, structural, and electrical characteristics of aluminum oxide thin films deposited by pulsed ultrasonic sprayed pyrolysis are reported. The films are deposited on crystalline silicon at temperatures from 400 to 550°C using a chemical solution of aluminum acetylacetonate, as source of aluminum, and N, N-dimethylformamide, as solvent. A H2O–NH4OH mist is supplied simultaneously during deposition to improve the films’ properties. The results showed that the properties of the as deposited films depended strongly on the number of pulses used and on the substrate temperature. The thickness of the films is under 300 Å and the best films’ properties showed an index of refraction close to 1.6 and a root mean square surface roughness of about 7.5 Å in average. Infrared spectroscopy shows that SiO2 is observed at the interface with silicon of the Al2O3 films and seemed to play, as expected, a dramatic role in the electrical characteristics of the interface. Films with a dielectric constant higher than 8 and an interface trap density at midgap in the 1010 eV−1 cm−2 range are obtained. Films deposited with three pulses and at 550 °C are able to stand an electric field up to 4 MV/cm.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.aj Insulators
78.66.Nk Insulators
73.61.Ng Insulators

HfO2 gate dielectric on (NH4)2S passivated (100) GaAs grown by atomic layer deposition

P. T. Chen, Y. Sun, E. Kim, P. C. McIntyre, W. Tsai, M. Garner, P. Pianetta, Y. Nishi, and C. O. Chui

J. Appl. Phys. 103, 034106 (2008); http://dx.doi.org/10.1063/1.2838471 (6 pages) | Cited 26 times

Online Publication Date: 7 February 2008

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The interface between hafnium oxide grown by atomic layer deposition and (100) GaAs treated with HCl cleaning and (NH4)2S passivation has been characterized. Synchrotron radiation photoemission core level spectra indicated successful removal of the native oxides and formation of passivating sulfides on the GaAs surface. Layer-by-layer removal of the hafnia film revealed a small amount of As2O3 formed at the interface during the dielectric deposition. Traces of arsenic and sulfur out diffusion into the hafnia film were observed after a 450 °C postdeposition anneal and may be the origins for the electrically active defects. Transmission electron microscopy cross section images showed thicker HfO2 films for a given precursor exposure on sulfur treated GaAs versus the nontreated sample. In addition, the valence-band and the conduction-band offsets at the HfO2/GaAs interface were deduced to be 3.18 eV and a range of 0.87–1.36 eV, respectively. It appears that HCl+(NH4)2S treatments provide a superior chemical passivation for GaAs and initial surface for atomic layer deposition.
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77.55.-g Dielectric thin films
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.aj Insulators
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.20.At Surface states, band structure, electron density of states

Lead-free piezoceramics with giant strain in the system Bi0.5Na0.5TiO3–BaTiO3–K0.5Na0.5NbO3. I. Structure and room temperature properties

Shan-Tao Zhang, Alain Brice Kounga, Emil Aulbach, Torsten Granzow, Wook Jo, Hans-Joachim Kleebe, and Jürgen Rödel

J. Appl. Phys. 103, 034107 (2008); http://dx.doi.org/10.1063/1.2838472 (8 pages) | Cited 56 times

Online Publication Date: 12 February 2008

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Lead-free piezoelectric ceramics, (1−x−y)Bi0.5Na0.5TiO3–xBaTiO3–yK0.5Na0.5NbO3 (0.05 ⩽ x ⩽ 0.07 and 0.01 ⩽ y ⩽ 0.03), have been synthesized by a conventional solid state sintering method. The room temperature ferroelectric and piezoelectric properties of these ceramics were studied. Based on the measured properties, the ceramics were categorized into two groups: group I compositions having dominant ferroelectric order and group II compositions displaying mixed ferroelectric and antiferroelectric properties at room temperature. A composition from group II near the boundary between these two groups exhibited a strain as large as ∼ 0.45% at an electric field of 8 kV/mm. Polarization in this composition was not stable in that the piezoelectric coefficient d33 at zero electric field was only about 30 pm/V. The converse piezoelectric response becomes weaker when the composition deviated from the boundary between the groups toward either the ferroelectric or antiferroelectric compositions. These results were rationalized based on a field induced antiferroelectric-ferroelectric phase transition.
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77.65.Ly Strain-induced piezoelectric fields
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Lead-free piezoceramics with giant strain in the system Bi0.5Na0.5TiO3–BaTiO3–K0.5Na0.5NbO3. II. Temperature dependent properties

Shan-Tao Zhang, Alain Brice Kounga, Emil Aulbach, Wook Jo, Torsten Granzow, Helmut Ehrenberg, and Jürgen Rödel

J. Appl. Phys. 103, 034108 (2008); http://dx.doi.org/10.1063/1.2838476 (7 pages) | Cited 44 times

Online Publication Date: 12 February 2008

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The temperature dependence of the dielectric and ferroelectric properties of lead-free piezoceramics of the composition (1−x−y)Bi0.5Na0.5TiO3–xBaTiO3–yK0.5Na0.5NbO3 (0.05 ⩽ x ⩽ 0.07, 0.01 ⩽ y ⩽ 0.03) was investigated. Measurements of the polarization and strain hystereses indicate a transition to predominantly antiferroelectric order when heating from room temperature to 150 °C, while for 150<T<200 °C both remnant polarization and coercive field increase. Frequency-dependent susceptibility measurements show that the transition is relaxorlike. For some samples, the transition temperature Td is high enough to allow mostly ferroelectric ordering at room temperature. These samples show a drastic increase of the usable strain under an external electric field just after the transition into the antiferroelectric state at high temperatures. For the other samples, Td is so low that they display significant antiferroelectric ordering already at room temperature. In these samples, the usable strain is relatively stable over a wide temperature range. In contrast to Td, the temperature Tm of the transition into the paraelectric high-temperature phase depends far less on the sample composition. These results confirm that the high strain in this lead-free system is due to a field-induced antiferroelectric-ferroelectric phase transition and that this effect can be utilized in a wide temperature range.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Ly Strain-induced piezoelectric fields
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point

Etching characteristics of LiNbO3 in reactive ion etching and inductively coupled plasma

Z. Ren, P. J. Heard, J. M. Marshall, P. A. Thomas, and S. Yu

J. Appl. Phys. 103, 034109 (2008); http://dx.doi.org/10.1063/1.2838180 (8 pages) | Cited 13 times

Online Publication Date: 12 February 2008

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The etching characteristics of congruent LiNbO3 single crystals including doped LiNbO3 and proton-changed LiNbO3 have been studied in reactive ion etching (RIE) and inductively coupled plasma (ICP) etching tools, using different recipes of gas mixtures. The effects of parameters including working pressure, RIE power, and ICP power are investigated and analyzed by measurement of etching depth, selectivity, uniformity, etched surface state, and sidewall profile by means of focused ion beam etching, energy-dispersive x-ray analysis, secondary ion mass spectroscopy, scanning electron microscopy, and surface profilometry. The effects of a sample carrier wafer coating have also been investigated. Optimized processes with high etching rates, good mask selectivity, and a near-vertical profile have been achieved. Ridge waveguides on proton-exchanged LiNbO3 have been fabricated and optically measured.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
73.20.At Surface states, band structure, electron density of states
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
42.70.-a Optical materials
42.82.Et Waveguides, couplers, and arrays

Low-temperature dielectric properties of Langmuir–Blodgett ferroelectric polymer films

X. J. Meng, H. Kliem, T. Lin, and J. H. Chu

J. Appl. Phys. 103, 034110 (2008); http://dx.doi.org/10.1063/1.2838212 (4 pages) | Cited 7 times

Online Publication Date: 12 February 2008

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Dielectric properties of the copolymer of vinylidene fluoride and trifluoroethylene films derived from the Langmuir–Blodgett technology have been investigated over the temperature range from 300 to 150 K at various frequencies. Below ∼ 240 K, peaks in the dielectric loss were observed to increase with increasing frequency. Nonlinear dielectric susceptibility and ferroelectric properties have been studied at different temperatures. The results show that the nonlinear dielectric susceptibility undergoes a remarkable change at ∼ 230 K. The results suggest a β relaxation, which is related to the freezing of the molecular motions in the amorphous phase in the polymer films. The anomaly in the electrical properties at ∼ 230 K is due to the freezing of the molecular chains motions.
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77.84.Jd Polymers; organic compounds
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials

Modeling and simulation for effective permittivity of two-phase disordered composites

Yonghong Cheng, Xiaolin Chen, Kai Wu, Shengnan Wu, Yu Chen, and Yongmeng Meng

J. Appl. Phys. 103, 034111 (2008); http://dx.doi.org/10.1063/1.2838465 (8 pages) | Cited 5 times

Online Publication Date: 12 February 2008

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We present a simulation for the effective permittivity of two-phase disordered composites based on a three-dimensional disordered model. In this model, the inclusions can be arranged at random positions in a composite material that is simulated by 10×10×10 cubic cells. Under the condition of the quasistatic approximation, numerical calculations are performed using the finite element method. The dependence of the calculated effective permittivity on the orientation of the disordered model is investigated. In order to get the macroscopical dielectric properties of isotropic composites, an averaging method is adopted because each topological structure of the disordered model is anisotropic. Then, the effect of the permittivity contrast between the inclusions and the matrix phase of composites is studied. The numerical results obtained by the disordered model are also compared with those obtained by the classical mixing rules and the conventional periodic models. The advantage of this presented disordered model is that it can succeed in predicting the effective permittivity in the cases of high permittivity contrast and large volume fractions of inclusions by considering overlapping of inclusions.
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77.22.Ch Permittivity (dielectric function)
77.84.Lf Composite materials
61.43.-j Disordered solids

Thermodynamic analysis of stress effect on Bi4Ti3O12 films

Li-Ben Li, Xia-Mei Lu, Qing-Dong Chen, Xiu-Mei Wu, and Jin-Song Zhu

J. Appl. Phys. 103, 034112 (2008); http://dx.doi.org/10.1063/1.2840066 (5 pages) | Cited 5 times

Online Publication Date: 13 February 2008

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Thermodynamic theory is applied to study the effect of stress on the polarization of Bi4Ti3O12 films with a two-dimensional model. The spontaneous polarizations and free energies are calculated for three possible kinds of orientations of the Bi4Ti3O12 cell and nine ferroelectric phases in the Bi4Ti3O12 films. The stress effect on the spontaneous polarization caused by the lattice distortion is small and can be neglected for all the stable ferroelectric phases, whereas the domain reorientation induced by the competition between the external stress and a gradient intrinsic stress leads to a significant change of spontaneous polarization in Bi4Ti3O12 films. The calculation result agrees well with the experimental result on Nd-doped Bi4Ti3O12 films.
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65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
77.80.-e Ferroelectricity and antiferroelectricity
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
77.55.-g Dielectric thin films

Direct electrical characterization of embedded ferroelectric lead titanate nanoislands

S. Clemens, A.-C. Dippel, T. Schneller, R. Waser, A. Rüdiger, and S. Röhrig

J. Appl. Phys. 103, 034113 (2008); http://dx.doi.org/10.1063/1.2838346 (4 pages) | Cited 3 times

Online Publication Date: 13 February 2008

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We report on the fabrication and characterization of lead titanate nanoislands on platinized silicon substrates embedded into a low-k dielectric. Our findings with Pt and Au as collective top electrodes are compared to previous results and thin films, and we discuss the coercive field and the remanent polarization with special care devoted to capacitive and leakage contributions of the nonpolar matrix. A direct electrical characterization of sub-100-nm ferroelectric nanoislands becomes feasible if they are measured in parallel, providing that the thin film material parameters of both ferroelectric and spin-on glass are independently determined.
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81.16.-c Methods of micro- and nanofabrication and processing
77.22.Ej Polarization and depolarization
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Dielectric properties and relaxor behavior of a new (1−x)BaTiO3–xBiAlO3 solid solution

Huichun Yu and Zuo-Guang Ye

J. Appl. Phys. 103, 034114 (2008); http://dx.doi.org/10.1063/1.2838479 (5 pages) | Cited 30 times

Online Publication Date: 13 February 2008

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A new lead-free perovskite solid solution of (1−x)BaTiO3–xBiAlO3 (x = 0.02, 0.05, 0.10, and 0.15) that exhibits ferroelectric properties and relaxor behavior has been synthesized by solid state reactions. X-ray diffraction patterns show a transformation from the tetragonal symmetry into a rhombohedral symmetry as a result of the substitutions of Bi3+ on the A site and Al3+ on the B site in the crystal lattice of BaTiO3. The temperature and frequency dependences of the dielectric constant indicate a crossover from a normal ferroelectric to relaxor behavior. The degree of deviation from the Curie–Weiss law is found to increase with the increasing amount of BiAlO3. The high-temperature slope of the dielectric peak for x = 0.05, 0.1 and, 0.15 can be well described by a Lorenz-type relation. Typical relaxor behavior is observed for x = 0.15 with the temperature of the dielectric peak Tm = 360 K at 1 kHz, while ferroelectric hysteresis loop is displayed at room temperature. This suggests that the long-range polar order from the end member BaTiO3 persists and coexists with polar nanoregions induced by the chemical disorder following the coupled substitutions in the solid solution.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)
64.70.K- Solid-solid transitions

High- and low-field dielectric characteristics of dielectrophoretically aligned ceramic/polymer nanocomposites

V. Tomer, C. A. Randall, G. Polizos, J. Kostelnick, and E. Manias

J. Appl. Phys. 103, 034115 (2008); http://dx.doi.org/10.1063/1.2838481 (7 pages) | Cited 14 times

Online Publication Date: 13 February 2008

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Polymer/ceramic composites with controlled spatial distribution of fillers are synthesized, and the corresponding changes in their properties are studied. Using dielectrophoretic assembly, we create anisotropic composites of aligned BaTiO3 particles in silicone elastomer and study their electrical properties as a function of ceramic volume fraction and composite morphology. These structured composites show an increase in the permittivity compared to composites with the same composition and randomly dispersed (0–3) fillers. This study emphasizes the important role of conductivity, permittivity, and, particularly, local cluster distribution in controlling high-field dielectric behavior. Designed anisotropy in dielectric properties can provide unexampled paradigms for the development of high energy density materials and gain important insights into the mechanisms that control dielectric breakdown strengths and nonlinear conduction at high fields in polymer/ceramic composites.
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77.22.Ch Permittivity (dielectric function)
77.22.Jp Dielectric breakdown and space-charge effects
77.84.Lf Composite materials
81.05.Qk Reinforced polymers and polymer-based composites

Effects of an external electric field on the ferroelectric-paraelectric phase transition in polyvinylidene fluoride-trifluoroethylene copolymer Langmuir–Blodgett films

Matt Poulsen, A. V. Sorokin, S. Adenwalla, Stephen Ducharme, and V. M. Fridkin

J. Appl. Phys. 103, 034116 (2008); http://dx.doi.org/10.1063/1.2838484 (9 pages) | Cited 4 times

Online Publication Date: 13 February 2008

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X-ray diffraction and capacitance measurements have been employed to study the structural and dielectric behavior of the ferroelectric-paraelectric phase transition under the influence of a large external electric field. The samples under study are ultrathin (15–100 nm) Langmuir–Blodgett films of a copolymer of vinylidene fluoride (70%) with trifluoroethylene (30%) deposited on aluminum-coated silicon. In situ θ-2θ x-ray diffraction was used to measure the change in interlayer spacing perpendicular to the film surface, corresponding to the (110) direction and indicating that the polymer chains along (001) lie predominantly in the plane, while capacitance measurements were used to monitor the behavior of the dielectric constant of the film. Application of a large electric field, up to 265 MV/m, raises the phase transition temperature and can convert the nonpolar trans-gauche paraelectric phase to the polar all-trans ferroelectric phase in a reversible manner.
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77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
61.41.+e Polymers, elastomers, and plastics
82.35.Jk Copolymers, phase transitions, structure
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces

A modified field model of waveguide reflection dielectric resonator for microwave measurements of dielectric properties

Jyh Sheen

J. Appl. Phys. 103, 034117 (2008); http://dx.doi.org/10.1063/1.2838489 (8 pages) | Cited 1 time

Online Publication Date: 13 February 2008

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A modified electromagnetic field model of a waveguide reflection dielectric resonator is suggested for measurements of dielectric properties of the homogeneous and isotropic medium in the microwave frequencies. Reflection signal is measured for the calculations of dielectric properties. A dielectric rod sample is put inside of a rectangular cavity made by a microwave waveguide. The sample’s dielectric constant and loss tangent are computed from the unloaded quality factor and the resonant frequency of the TE01δ mode as well as the structure dimensions. For first time, this waveguide reflection dielectric resonator is applied on dielectric constant measurement. A modified field model of the waveguide reflection resonator is developed from the Itoh-Rudokas model [ IEEE Trans. Microwave Theory Tech. MTT-25, 52 (1977) ] of the parallel-plate dielectric resonator. This modification is justified by the dramatic improvement in the accuracy of dielectric constant measurements. The main merit of this field model is that it provides very simple electromagnetic field expressions of this TE01δ field mode. In addition, accuracies of various methods for calculating the power factor and conducting loss, which have never been given before, will be investigated in this article.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.40.Az Waveguides, transmission lines, striplines
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

LaAlO3 gate dielectric with ultrathin equivalent oxide thickness and ultralow leakage current directly deposited on Si substrate

Masamichi Suzuki, Takeshi Yamaguchi, Noburu Fukushima, and Masato Koyama

J. Appl. Phys. 103, 034118 (2008); http://dx.doi.org/10.1063/1.2838470 (5 pages) | Cited 13 times

Online Publication Date: 15 February 2008

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By a careful choice of film deposition conditions, LaAlO3 (LAO) gate dielectric film with equivalent oxide thickness (EOT) of 0.31 nm and gate leakage current density (Jg) of 0.1 A/cm2 (at Vfb+1 V) has been successfully demonstrated. Elimination of interfacial low-k layer at LAO/Si and reduction of defect density in LAO has been realized through both LAO film deposition at high-temperature (700 °C) and subsequent low-temperature (200 °C) annealing. By using thermal desorption spectroscopy technique, we find that our process reduces remnant H2O or OH− species in the LAO film, which are responsible for the degradation of EOT and Jg.
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77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition
81.40.Gh Other heat and thermomechanical treatments
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.55.aj Insulators
68.43.Vx Thermal desorption

Film thickness dependence of electrocaloric effect in epitaxial Ba0.6Sr0.4TiO3 thin films

J. H. Qiu and Q. Jiang

J. Appl. Phys. 103, 034119 (2008); http://dx.doi.org/10.1063/1.2838485 (6 pages) | Cited 3 times

Online Publication Date: 15 February 2008

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Based on the phenomenological Landau–Devonshire thermodynamic theory, the film thickness dependence of electrocaloric effect in epitaxial Ba0.6Sr0.4TiO3 thin films is investigated. Theoretical analysis shows that the Ba0.6Sr0.4TiO3 thin films grown on LaAlO3 and MgO substrates have the giant electrocaloric effect at room temperature. Our theoretical calculations also indicate that the entropy and electrocaloric effect strongly depend on film thickness.
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77.70.+a Pyroelectric and electrocaloric effects
68.55.jd Thickness
05.70.Ce Thermodynamic functions and equations of state
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