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15 Aug 2005

Volume 98, Issue 4, Articles (04xxxx)

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A low loss, dielectric substrate in ZnAl2O4–TiO2 system for microelectronic applications

K. P. Surendran, M. T. Sebastian, M. V. Manjusha, and Jacob Philip

J. Appl. Phys. 98, 044101 (2005); http://dx.doi.org/10.1063/1.2007873 (5 pages) | Cited 11 times

Online Publication Date: 16 August 2005

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A temperature stable low loss substrate based on 0.83ZnAl2O4–0.17TiO2 (ZAT) was developed as a substitute to Al2O3 for possible applications in microelectronic industry as substrates and packaging materials. The thermal conductivity of ZAT is 59 W m−1 K−1 which is more than twice as that of Al2O3. The thermal-expansion coefficient of this dielectric is 6.3 ppm/°C which is comparable to that of silicon used in microelectronic circuitry. Furthermore, 0.83ZnAl2O4–0.17TiO2 dielectric is chemically inert with silicon, which increases its applicability in microelectronic packages.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
65.40.De Thermal expansion; thermomechanical effects
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

The importance of network structure in high-k dielectrics: LaAlO3, Pr2O3, and Ta2O5

T. Busani and R. A. B. Devine

J. Appl. Phys. 98, 044102 (2005); http://dx.doi.org/10.1063/1.2012513 (5 pages) | Cited 9 times

Online Publication Date: 19 August 2005

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Measurements of the dielectric constant of amorphous and crystalline Pr2O3 are reported. The high value ∼ 25 for the polycrystalline phase is discussed in terms of the network structure and comparison is made with heavy rare-earth oxide values. The specific cases of LaAlO3 and Ta2O5 are also discussed and the role of network structure evidenced and elucidated. A potential route to finding high k materials suitable for microelectronics applications is suggested.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.22.Ch Permittivity (dielectric function)
68.55.-a Thin film structure and morphology
61.43.Er Other amorphous solids

The charge trapping effect of metal-ferroelectric (PbZr0.53Ti0.47O3)-insulator (HfO2)-silicon capacitors

Pi-chun Juan, Yu-ping Hu, Fu-chien Chiu, and Joseph Ya-min Lee

J. Appl. Phys. 98, 044103 (2005); http://dx.doi.org/10.1063/1.2014935 (6 pages) | Cited 14 times

Online Publication Date: 22 August 2005

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Metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with a Pb(Zr0.53,Ti0.47)O3 ferroelectric layer and a hafnium oxide insulator layer have been fabricated and characterized. The size of the capacitance-voltage memory windows was investigated. The memory window first increases to a saturated value of 0.7 V with the sweep voltage and then decreases due to charge injection. The oxide trapped charges in the ferroelectric∕insulator layers are studied by a voltage stress method. The flatband voltage (VFB) is measured before and after the voltage stress. The ΔVFB is 0.59 V at a negative stress voltage pulse of −5 V for 30 s. The ΔVFB under positive voltage stress was much less and was 0.06 V at a stress voltage of +5 V for 5 min. The energy-band diagram of the MFIS structure at inversion and accumulation modes are plotted and the VFB shift can be explained by the trapping or detrapping of charges. The current-density versus stress time (J‐t) characteristics were also measured. The result is consistent with the charge trapping model.
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85.50.Gk Non-volatile ferroelectric memories
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Studies of high-temperature phase transition, electrical conductivity, and dielectric relaxation in (NH4)H2PO4 single crystal

R. H. Chen, Chen-Chieh Yen, C. S. Shern, and T. Fukami

J. Appl. Phys. 98, 044104 (2005); http://dx.doi.org/10.1063/1.2009074 (7 pages) | Cited 2 times

Online Publication Date: 23 August 2005

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Optical observation, differential scanning calorimetry, thermogravimetric analysis, and differential thermogravimetric measurements have been carried out on (NH4)H2PO4 single crystal in the temperature range of 30–250 °C. The results show that the crystal starts to decompose at around 160 °C. Upon heating, ammonia NH3 escapes from the surface of the crystal gradually with the production of phosphoric acid. The measured ac impedance data are analyzed as a function of frequency in the temperature range between 40 and 150 °C. The frequency dependence of conductivity follows Jonscher’s dynamical law with the relation σ(ω) = σ(0)+Bωn, where ω is the frequency of the applied ac electric field and B is a constant. The obtained values of the exponent n decrease from 1 to 0.25 as the temperature is raised. The electrical conduction at low temperatures below 70 °C is attributed to the hopping of proton on O–H–O hydrogen bonds among hydrogen vacancies. The activation energy of the migration is 0.12 eV in this extrinsic region. At temperatures between 70 and 97 °C, additional defects are created by breaking the stronger hydrogen bond in ammonium groups. The activation energy of defect formation and migration of proton among defects is 0.83 eV. At temperatures above 97 °C, ammonium ions in the crystal are proposed to have the contribution to the electrical conduction with an activation energy of 3.01 eV.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Gm Dielectric loss and relaxation
72.20.Ee Mobility edges; hopping transport
72.80.Sk Insulators
61.72.J- Point defects and defect clusters
64.70.K- Solid-solid transitions
81.40.Gh Other heat and thermomechanical treatments

Growth kinetics of core-shell-structured grains and dielectric constant in rare-earth-doped BaTiO3 ceramics

Gang Liu, Xiao-hui Wang, Y. Lin, L.-T. Li, and Ce-Wen Nan

J. Appl. Phys. 98, 044105 (2005); http://dx.doi.org/10.1063/1.2030413 (6 pages) | Cited 8 times

Online Publication Date: 23 August 2005

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The solute-drag-dependent growth kinetics of core-shell-structured grains in rare-earth-doped BaTiO3 ceramics was studied based on an analytical description of the diffusion of rare-earth atoms doped. Dependence of the sizes of grain core and shell on the sintering conditions, dopant content, and starting powder size was quantitatively revealed. The effective dielectric constant of the ceramics was calculated in terms of the relative contents of the ferroelectric core and paraelectric shell. The calculations are in good agreement with the experimental observations.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.80.-e Ferroelectricity and antiferroelectricity
66.30.J- Diffusion of impurities
61.72.up Other materials

Micro-Brillouin scattering study of ferroelectric relaxor Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 single crystals under the electric field along the [001] direction

Do Han Kim, Jae-Hyeon Ko, C. D. Feng, and Seiji Kojima

J. Appl. Phys. 98, 044106 (2005); http://dx.doi.org/10.1063/1.2008353 (5 pages) | Cited 8 times

Online Publication Date: 24 August 2005

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Electric-field effects on structural phase transitions have been studied in ferroelectric relaxor Pb[(Zn1/3Nb2/3)1−xTix]O3 single crystals with x = 0.09 by the high-resolution micro-Brillouin scattering. Sharp phase transitions from cubic-to-tetragonal and then from tetragonal-to-rhombohedral phases have been observed under zero-field-cooling (ZFC) condition. For two phase-transition temperatures a noticeable thermal hysteresis was clearly observed, consistent with dielectric measurements. The temperature range of a tetragonal phase has been markedly extended under the electric field of E = 6.7 kV/cm along the [001] direction. A large difference of the LA-mode frequency and damping between the ZFC and field-cooling processes indicated that the multidomain structure induces the increase of the acoustic damping due to the elastic scattering. In addition, it was found that the elastic stiffness coefficient c33 in the tetragonal coordinates shows a slight decrease. The first-order character of the cubic-to-tetragonal phase transition has been gradually changed into a second-order one under the increase of the electric field along the [001] direction, reflecting a general trend of the first-order ferroelectric phase transition. Although a clear specification of the low-temperature symmetry could not be accomplished from Brillouin scattering itself, these results give new insights into an electric-field-temperature phase diagram containing phase boundaries among cubic, tetragonal, and low-temperature phases.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.35.+c Brillouin and Rayleigh scattering; other light scattering
77.80.B- Phase transitions and Curie point
64.70.K- Solid-solid transitions
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
62.20.D- Elasticity
61.66.Fn Inorganic compounds
77.80.Dj Domain structure; hysteresis

Pyroelectric study of polarization switching in Langmuir-Blodgett films of poly(vinylidene fluoride trifluoroethylene)

A. V. Sorokin, V. M. Fridkin, and Stephen Ducharme

J. Appl. Phys. 98, 044107 (2005); http://dx.doi.org/10.1063/1.2006228 (10 pages) | Cited 17 times

Online Publication Date: 24 August 2005

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The ferroelectric switching in Langmuir-Blodgett films of poly(vinylidene fluoride trifluoroethylene) is studied. The films have a distribution of switching times several decades wide. Nearly a half of the film volume may be switched faster than 1 ms, though complete switching of a whole sample may require 100 s or more. The switching occurs through a domain nucleation and growth mechanism. The decay of polarization at zero bias is logarithmic in time, with a constant rate below 5% per decade at room temperatures. The coercive voltage may be as low as 5 V, which makes the films promising for use in nonvolatile random-access data storage.
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77.84.Jd Polymers; organic compounds
77.70.+a Pyroelectric and electrocaloric effects
77.80.Fm Switching phenomena
77.55.-g Dielectric thin films
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
77.80.Dj Domain structure; hysteresis
73.61.Ph Polymers; organic compounds
77.22.Ej Polarization and depolarization
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