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16 Apr 2001

Volume 78, Issue 16, pp. 2267-2404

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Dependence of dielectric properties on internal stresses in epitaxial barium strontium titanate thin films

Hao Li, A. L. Roytburd, S. P. Alpay, T. D. Tran, L. Salamanca-Riba, and R. Ramesh

Appl. Phys. Lett. 78, 2354 (2001); http://dx.doi.org/10.1063/1.1359141 (3 pages) | Cited 83 times

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A series of heteroepitaxial BaxSr1−xTiO3 thin films with composition x = 0.50 were deposited on (001) MgO substrates by pulsed-laser deposition. The thickness of the films was varied from 14 to 500 nm to produce a systematically decreasing level of in-plane tensile stresses. The microstructural and crystallographic features of the films were determined via transmission electron microscopy and x-ray diffraction. A theoretical treatment of the in-plane misfit strain as a function of film thickness is in agreement with the measured out-of-plane lattice parameters. Electrical measurements indicate a drop in the dielectric constant from 2350 for highly stressed thin films to 1700 for relaxed thicker films. The variation in the dielectric constant with the misfit strain is in accordance with a thermodynamic model developed. The relationship between the dielectric constant and electric field is also described by extending the thermodynamic model and taking the effect of electric field into account. A new definition of tunability is adopted to study the effect of strain on tunability. © 2001 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.60.Bs Mechanical and acoustical properties
77.22.Ch Permittivity (dielectric function)

Electrical and materials properties of ZrO2 gate dielectrics grown by atomic layer chemical vapor deposition

Charles M. Perkins, Baylor B. Triplett, Paul C. McIntyre, Krishna C. Saraswat, Suvi Haukka, and Marko Tuominen

Appl. Phys. Lett. 78, 2357 (2001); http://dx.doi.org/10.1063/1.1362331 (3 pages) | Cited 98 times

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Structural and electrical properties of gate stack structures containing ZrO2 dielectrics were investigated. The ZrO2 films were deposited by atomic layer chemical vapor deposition (ALCVD) after different substrate preparations. The structure, composition, and interfacial characteristics of these gate stacks were examined using cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy. The ZrO2 films were polycrystalline with either a cubic or tetragonal crystal structure. An amorphous interfacial layer with a moderate dielectric constant formed between the ZrO2 layer and the substrate during ALCVD growth on chemical oxide-terminated silicon. Gate stacks with a measured equivalent oxide thickness (EOT) of 1.3 nm showed leakage values of 10−5 A/cm2 at a bias of −1 V from flatband, which is significantly less than that seen with SiO2 dielectrics of similar EOT. A hysteresis of 8–10 mV was seen for ±2 V sweeps while a midgap interface state density (Dit) of ∼ 3×1011 states/cm eV was determined from comparisons of measured and ideal capacitance curves. © 2001 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.60.Dp Adsorbed layers and thin films
61.66.Fn Inorganic compounds
77.22.Ch Permittivity (dielectric function)
73.20.At Surface states, band structure, electron density of states
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Ferroelectric and electromechanical properties of poly(vinylidene-fluoride–trifluoroethylene–chlorotrifluoroethylene) terpolymer

Haisheng Xu, Z.-Y. Cheng, Dana Olson, T. Mai, Q. M. Zhang, and G. Kavarnos

Appl. Phys. Lett. 78, 2360 (2001); http://dx.doi.org/10.1063/1.1358847 (3 pages) | Cited 66 times

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See Also: Erratum

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This letter reports the ferroelectric and electromechanical properties of a class of ferroelectric polymer, poly(vinylidene-fluoride–trifluoroethylene–chlorotrifluoroethylene) terpolymer, which exhibits a slim polarization hysteresis loop and a high electrostrictive strain at room temperature. The dielectric and polarization behaviors of this terpolymer are typical of the ferroelectric relaxor. The x-ray and Fourier transform infrared results reveal that the random incorporation of bulky chlorotrifluoroethylene (CTFE) ter-monomers into polymer chains causes disordering of the ferroelectric phase. Furthermore, CTFE also acts as random defect fields which randomize the inter- and intrachain polar coupling, resulting in the observed ferroelectric relaxor behavior. © 2001 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Jd Polymers; organic compounds
77.22.Ej Polarization and depolarization
77.65.Fs Electromechanical resonance; quartz resonators
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
77.65.Bn Piezoelectric and electrostrictive constants

Effect of microstructures on the microwave dielectric properties of ZrTiO4 thin films

Yongjo Kim, Jeongmin Oh, Tae-Gon Kim, and Byungwoo Park

Appl. Phys. Lett. 78, 2363 (2001); http://dx.doi.org/10.1063/1.1366359 (3 pages) | Cited 27 times

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To obtain various paraelectric ZrTiO4 thin-film microstructures, the films were synthesized at different deposition temperatures using rf magnetron sputtering. Both the dielectric losses (tan δ) and dielectric constants (ϵ) of the ZrTiO4 thin films were measured up to 6 GHz using a circular-patch capacitor geometry. The films showed enhanced crystallinity with increasing deposition temperature, as determined from the x-ray diffraction peak widths at various scattering vectors. The microwave dielectric losses correlated very well with the level of crystallinity or strain, while the dielectric constants did not alter significantly. © 2001 American Institute of Physics.
Show PACS
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
61.72.-y Defects and impurities in crystals; microstructure
68.60.Bs Mechanical and acoustical properties
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