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7 Jan 2008

Volume 92, Issue 1, Articles (01xxxx)

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Appl. Phys. Lett. 92, 011101 (2008); http://dx.doi.org/10.1063/1.2828458 (3 pages)

F. Pedaci, S. Barland, E. Caboche, P. Genevet, M. Giudici, J. R. Tredicce, T. Ackemann, A. J. Scroggie, W. J. Firth, G.-L. Oppo, G. Tissoni, and R. Jäger
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Epitaxial La2Hf2O7 thin films on Si(001) substrates grown by pulsed laser deposition for high-k gate dielectrics

Feng Wei, Hailing Tu, Yi Wang, Shoujing Yue, and Jun Du

Appl. Phys. Lett. 92, 012901 (2008); http://dx.doi.org/10.1063/1.2828692 (3 pages) | Cited 8 times

Online Publication Date: 2 January 2008

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The La2Hf2O7 (LHO) films have been epitaxially grown on Si(001) substrates using an ultrahigh vacuum pulsed laser deposition system. X-ray diffraction characterization shows the predominant orientation of the LHO film grown at 780 °C is (001)LHO∥(001)Si and [110]LHO∥[110]Si. High-resolution transmission electron microscopy results illustrate that the epitaxial LHO film with high crystallinity is in pure pyrochlore phase and has an unobservable interfacial layer between Si and LHO. The electrical characterization of metal-insulator-semiconductors reveals that the epitaxial LHO film has a dielectric constant of approximately 22, an acceptable gate leakage current density and a negligible hysteresis in capacitance-voltage characterization.
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81.15.Fg Pulsed laser ablation deposition
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis

Characteristics of the low electron density surface layer on BaTiO3 thin films

X. L. Li, H. B. Lu, Ming Li, Zhenhong Mai, Hyunjung Kim, and Q. J. Jia

Appl. Phys. Lett. 92, 012902 (2008); http://dx.doi.org/10.1063/1.2828339 (3 pages) | Cited 6 times

Online Publication Date: 2 January 2008

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The surfaces of epitaxial BaTiO3 films on SrTiO3 substrates were investigated by x-ray reflectivity (XRR) and angle-resolved x-ray photoelectron spectroscopy (ARXPS). It was shown by XRR analysis that there exists a low electron density surface layer (about 87%–93% of the electron density of the underneath BaTiO3 layer) of 15 Å on top of the film. Moreover, ARXPS results revealed a surface core-level shift of Ba in layer of about 11 Å, a value which is in agreement with the thickness obtained by XRR, indicating that the surface core-level shift of Ba stems from the low electron density surface layer.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
79.60.Dp Adsorbed layers and thin films
73.25.+i Surface conductivity and carrier phenomena

High energy density metal-insulator-metal capacitors with Ba[(Ni1/2,W1/2)0.1Ti0.9]O3 thin films

N. K. Karan, J. J. Saavedra-Arias, M. Perez, R. Thomas, and R. S. Katiyar

Appl. Phys. Lett. 92, 012903 (2008); http://dx.doi.org/10.1063/1.2828700 (3 pages) | Cited 8 times

Online Publication Date: 2 January 2008

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Metal-insulator-metal capacitors with high-k Ba[(Ni1/2,W1/2)0.1Ti0.9]O3 thin film dielectrics were fabricated by chemical solution deposition technique. High dielectric constant (85), low dielectric loss (0.007), and high breakdown field ( ∼ 3.0 MV/cm) at room temperature were achieved. The temperature and frequency dependences of capacitance and loss tangent were small around room temperature (300±25 K). At room temperature, high capacitance density (3.1 fF/μm2) along with high energy density (34 J/cm3) and low leakage current (7.7×10−6 A/cm2 at 20 V) were obtained, indicating high potential for this material in the integrated circuits and power electronic applications.
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84.32.Tt Capacitors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Detection of phase transitions in sodium bismuth titanate–barium titanate single crystals by acoustic emission

E. Dul’kin, E. Mojaev, M. Roth, S. Greicius, and T. Granzow

Appl. Phys. Lett. 92, 012904 (2008); http://dx.doi.org/10.1063/1.2828698 (3 pages) | Cited 9 times

Online Publication Date: 2 January 2008

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Acoustic emission measurements are combined with strain, dielectric, and polarization measurements to detect phase transitions in 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 single crystals during thermal cycling as well as electric field cycling at both room temperature and 140 °C. All phase transitions known from the literature (cubic↔tetragonal↔trigonal I↔trigonal II) are determined to be of first order, and the existence of the ferroelectric trigonal II phase at room temperature and its transformation into an antiferroelectric phase during heating above 130 °C is established.
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77.22.Ej Polarization and depolarization
62.65.+k Acoustical properties of solids
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Ferroelectric and piezoelectric properties of 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 lead-free piezoelectric thick film by aerosol deposition

Jungho Ryu, Jong-Jin Choi, Byung-Dong Hahn, Dong-Soo Park, and Woon-Ha Yoon

Appl. Phys. Lett. 92, 012905 (2008); http://dx.doi.org/10.1063/1.2828892 (3 pages) | Cited 25 times

Online Publication Date: 2 January 2008

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Lead-free, piezoelectric thick films of 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 were fabricated by aerosol deposition and the effect of postannealing temperature on the dielectric, ferroelectric, and piezoelectric properties was investigated. The thickness of the films ranged from 5 to 17 μm and highly dense films were obtained after deposition at room temperature. With increasing annealing temperature, the dielectric and ferroelectric properties were markedly increased. The maximum ferroelectric and dielectric properties of ε3T/ε0 = 1012, Pr = 15.5 μC/cm2, and d33 = 50 pm/V were obtained after annealing at 800 °C for 1 h. Above this temperature, the film exhibited rapid property degradation as it was decomposed due to Na2O evaporation.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.-j Piezoelectricity and electromechanical effects
61.72.Cc Kinetics of defect formation and annealing
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Size-dependent ferroelectric behaviors of BaTiO3 nanowires

Jiawang Hong and Daining Fang

Appl. Phys. Lett. 92, 012906 (2008); http://dx.doi.org/10.1063/1.2830662 (3 pages) | Cited 30 times

Online Publication Date: 3 January 2008

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Landau-Ginsburg-Devonshire theory is introduced to investigate the size-dependent ferroelectric properties of BaTiO3 nanowires, with the consideration of polarization orienting along the radial direction. It is shown that the Curie temperature, mean polarization, and area enclosed by hysteresis loop decrease with the reducing diameter of the nanowire. However, this size effect becomes obvious only when the diameter is below 20 nm. Above this, the ferroelectric behaviors of nanowires are almost the same as those of bulk materials. Furthermore, there exists a temperature-dependent critical diameter for BaTiO3 nanowire below which the hysteresis loops vanish and it is 3.6 nm at room temperature.
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61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis

Giant piezoelectric d33 coefficient in ferroelectric vanadium doped ZnO films

Y. C. Yang, C. Song, X. H. Wang, F. Zeng, and F. Pan

Appl. Phys. Lett. 92, 012907 (2008); http://dx.doi.org/10.1063/1.2830663 (3 pages) | Cited 33 times

Online Publication Date: 3 January 2008

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A giant electromechanical d33 coefficient 110 pC/N is obtained in ferroelectric V-doped ZnO films, which is nearly one order of magnitude higher than that of undoped samples. It is considered that the switchable spontaneous polarization induced by V dopants and the accompanying relatively high permittivity should be responsible for the enhancement of piezoelectric response. Moreover, from another point of view, an easier rotation of V–O bonds which are noncollinear with c axis under electric field might be the microscopic origin of this anomaly. The improved piezoelectric properties could make V-doped ZnO a promising candidate for piezoelectric devices.
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77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization
77.80.Fm Switching phenomena
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

The effect of dopants on the dielectric constant of HfO2 and ZrO2 from first principles

Dominik Fischer and Alfred Kersch

Appl. Phys. Lett. 92, 012908 (2008); http://dx.doi.org/10.1063/1.2828696 (3 pages) | Cited 38 times

Online Publication Date: 3 January 2008

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Based on first-principles calculations, we elucidate the influence of dopants on the dielectric properties of the high-k materials HfO2 and ZrO2. Our calculations demonstrate that by doping the tetragonal phase can become energetically more favorable than the monoclinic phase present at ambient conditions. The stabilization of the tetragonal phase increases the dielectric constant significantly. A series of dopants was investigated to understand the efficiency and the mechanism of the stabilization process. The calculations reveal that at a moderate doping level ( ∼ 12%) only some of the dopants stabilize the tetragonal phase and that Si is the most efficient stabilizer atom.
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77.55.-g Dielectric thin films
61.72.up Other materials
77.22.Ch Permittivity (dielectric function)

Band bending and the thermochemistry of oxygen vacancies in ionic metal oxide thin films

S. Guha and P. Solomon

Appl. Phys. Lett. 92, 012909 (2008); http://dx.doi.org/10.1063/1.2828703 (3 pages) | Cited 10 times

Online Publication Date: 3 January 2008

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We address the problem of band bending in a metal oxide thin film/electrode layer and derive equations relating the voltage drop across the oxide to the oxygen activity of the ambient in equilibrium with the oxide. Applied to the case of oxygen vacancies, the results predict situations where the vacancy charge is strongly localized adjacent to the metal interface. Comparing predictions to experimental results for the specific case of HfO2, we find that the free energy of formation of the oxygen vacancies are of the order of ∼ 3 eV, significantly smaller than the numbers theoretically predicted for bulk HfO2.
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82.60.-s Chemical thermodynamics
65.40.G- Other thermodynamical quantities
71.20.-b Electron density of states and band structure of crystalline solids
61.72.jd Vacancies

Schottky-like behavior of progressive breakdown of polycrystalline- silicon/silicon oxynitride gate dielectric stack

V. L. Lo, K. L. Pey, and C. H. Tung

Appl. Phys. Lett. 92, 012910 (2008); http://dx.doi.org/10.1063/1.2829599 (3 pages) | Cited 1 time

Online Publication Date: 3 January 2008

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The postbreakdown (BD) I-V characteristics of a relatively stable percolation path within ultrathin silicon oxynitride have been found to exhibit Schottky-like behavior. The ideality factors in the range of 1.3–1.7 indicate that a Schottky-like barrier could exist in controlling the conduction mechanism in the later stage of progressive BD (PBD). The extracted effective barrier heights associated with the percolation path provides possible insights into the nature of the percolation path. We found that there are two possible mechanisms governing the post-BD I-V characteristics in the later stage of PBD: (1) a material property change in the vicinity of the percolation path and (2) the percolation path dilation.
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73.30.+y Surface double layers, Schottky barriers, and work functions
77.22.Jp Dielectric breakdown and space-charge effects

Effect of epitaxial strain on ferroelectric polarization in multiferroic BiFeO3 films

Dae Ho Kim, Ho Nyung Lee, Michael D. Biegalski, and Hans M. Christen

Appl. Phys. Lett. 92, 012911 (2008); http://dx.doi.org/10.1063/1.2830799 (3 pages) | Cited 63 times

Online Publication Date: 4 January 2008

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Multiferroic BiFeO3 epitaxial films with thicknesses ranging from 40 to 960 nm were grown by pulsed laser deposition on SrTiO3 (001) substrates with SrRuO3 bottom electrodes. X-ray characterization shows that the structure evolves from angularly distorted tetragonal with c/a ≈ 1.04 to more bulklike distorted rhombohedral (c/a ≈ 1.01) as the strain relaxes with increasing thickness. Despite this significant structural evolution, the ferroelectric polarization along the body diagonal of the distorted pseudocubic unit cells, as calculated from measurements along the normal direction, barely changes.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.22.Ej Polarization and depolarization
81.15.Fg Pulsed laser ablation deposition
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Electric surface potential and frozen-in field direct measurements in thermally poled silica

D. Yudistira, D. Faccio, C. Corbari, P. G. Kazansky, S. Benchabane, and V. Pruneri

Appl. Phys. Lett. 92, 012912 (2008); http://dx.doi.org/10.1063/1.2827175 (3 pages) | Cited 1 time

Online Publication Date: 4 January 2008

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We report measurements of the electric surface potential (SP) and its temporal evolution in thermally poled silica samples, thus, providing a direct quantitative evidence of the frozen-in voltage. The SP value is found to be directly related to the voltage across the depletion layer and there is a clear link between frozen-in electric field and nonlinear optical coefficient, inferred from SP and second harmonic generation measurements respectively. Our studies also show the presence of screening surface charge layers. We have calculated the space charge distribution making evident that the thinner the sample, the larger the screening surface charge density.
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77.22.Ej Polarization and depolarization
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Dependence of the structures and properties on LaAlO3 cap layer in LaAlO3/BaTiO3 superlattices

Changming Zuo, Shengbo Lu, Xun Zhou, and Yu Zhang

Appl. Phys. Lett. 92, 012913 (2008); http://dx.doi.org/10.1063/1.2830990 (3 pages) | Cited 1 time

Online Publication Date: 4 January 2008

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The LaAlO3/BaTiO3 artificial superlattices were fabricated on (001)-oriented Nb-doped SrTiO3 substrates by laser molecular-beam epitaxy. The structures of the superlattice were analyzed by normal θ-2θ scan mode x-ray diffraction analysis, high-resolution reciprocal space mapping measurement, and x-ray reflectivity measurement. The use of a LaAlO3 cap layer could effectively reduce dislocation formation at the interface, which released the strain induced by the lattice misfit between the sublayers. The surface and interface were also smoothed by the use of a LaAlO3 cap layer. Therefore, the strain was maintained in the film and the ferroelectric property of the superlattice was significantly enhanced.
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68.65.Cd Superlattices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Localized breakdown in dielectrics and macroscopic charge transport through the whole gate stack: A comparative study

Yi Zheng, Andrew T. S. Wee, Yi Ching Ong, K. L. Pey, Cedric Troadec, Sean J. O’Shea, and N. Chandrasekhar

Appl. Phys. Lett. 92, 012914 (2008); http://dx.doi.org/10.1063/1.2830814 (3 pages) | Cited 2 times

Online Publication Date: 7 January 2008

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Au–HfO2–SiOx–Si structures with 4 nm HfO2 and 1.5 nm SiOx interfacial layer (IL) have been electrically stressed by ballistic electron emission spectroscopy (BEES). The continuous BEES stressing at the same location induced gradual degradations and finally led to breakdowns in the IL. The degradation and breakdown cannot be observed using macroscopic conventional current-voltage (IV) measurements over the same area just before and after the BEES stressing process. The localized degradation and breakdown in the dielectric is masked by the macroscopic gate area. Tunneling calculations can estimate the critical area required for a macroscopic device to be able to measure such microscopic breakdown, a problem that becomes increasingly important for characterizing ultrathin gate dielectrics.
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73.40.Ns Metal-nonmetal contacts
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling

Epitaxial growth of HfO2 doped CeO2 thin films on Si(001) substrates for high-κ application

Yi Wang, Feng Wei, Shoujing Yue, Zhimin Yang, and Jun Du

Appl. Phys. Lett. 92, 012915 (2008); http://dx.doi.org/10.1063/1.2829792 (3 pages) | Cited 4 times

Online Publication Date: 7 January 2008

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The authors report on the growth and characterization of CeO2 epitaxial films doped with 18 at. % HfO2 (HDC) as gate dielectrics for Si technology prepared by ultrahigh vacuum pulsed laser deposition. In situ reflection high-energy electron diffraction and cross-sectional high-resolution transmission electron microscopy reveal the formation of an epitaxial HDC/Si structure with (111)HDC‖(001)Si and [110]HDC‖[110]Si orientation relationship. C-V and I-V measurements indicate a dielectric constant κ ∼ 19.5 for HDC film and the leakage current density at 1 V gate bias is about four orders of magnitude lower than that of the CeO2 in both 25 nm thickness.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.ag Semiconductors
77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition
68.37.Og High-resolution transmission electron microscopy (HRTEM)
77.22.Ch Permittivity (dielectric function)

Enhanced piezoelectric response from barium strontium titanate multilayer films

R. Nath, S. Zhong, S. P. Alpay, B. D. Huey, and M. W. Cole

Appl. Phys. Lett. 92, 012916 (2008); http://dx.doi.org/10.1063/1.2825287 (3 pages) | Cited 14 times

Online Publication Date: 7 January 2008

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Multilayered and homogeneous thin films of BaxSr1−xTiO3 (BST) were grown on Pt-coated Si substrates via metal-organic solution deposition. The multilayer 220 nm thick BST heterostructure consisted of Ba0.60Sr0.40TiO3, Ba0.75Sr0.25TiO3, and Ba0.90Sr0.10TiO3. A single composition 220 nm thick Ba0.60Sr0.40TiO3 was also grown for comparison. The piezoelectric properties were measured using piezoresponse force microscopy. There is approximately a 50% improvement in the piezoelectric response of the multilayered heterostructure compared to the homogeneous sample, with some spatial inhomogeneity. This enhancement can be attributed to the internal potential that arises from the polarization gradient and the commensurate built-in strain in the multilayer sample.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.65.Ly Strain-induced piezoelectric fields
77.22.Ej Polarization and depolarization
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.65.Ac Multilayers

Composition-dependent polarization switching behaviors of (111)-preferred polycrystalline Pb(ZrxTi1−x)O3 thin films

J. Y. Jo, S. M. Yang, H. S. Han, D. J. Kim, W. S. Choi, T. W. Noh, T. K. Song, J.-G. Yoon, C.-Y. Koo, J.-H. Cheon, and S.-H. Kim

Appl. Phys. Lett. 92, 012917 (2008); http://dx.doi.org/10.1063/1.2824839 (3 pages) | Cited 5 times

Online Publication Date: 8 January 2008

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We investigated the time-dependent polarization switching behaviors of (111)-preferred polycrystalline Pb(ZrxTi1−x)O3 thin films with various Zr concentrations. We could explain all the polarization switching behaviors well by assuming Lorentzian distributions in the logarithmic polarization switching time [refer to J. Y. Jo et al., Phys. Rev. Lett. 99, 267602 (2007) ]. Based on this analysis, we found that the Zr ion substitution for Ti ions would induce broad distributions in the local field due to defect dipoles, which makes the ferroelectric domain switching occur more easily.
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77.55.-g Dielectric thin films
77.80.Fm Switching phenomena
77.80.Dj Domain structure; hysteresis

Enhanced dielectric properties in single crystal-like BiFeO3 thin films grown by flux-mediated epitaxy

S.-H. Lim, M. Murakami, J. H. Yang, S.-Y. Young, J. Hattrick-Simpers, M. Wuttig, L. G. Salamanca-Riba, and I. Takeuchi

Appl. Phys. Lett. 92, 012918 (2008); http://dx.doi.org/10.1063/1.2831665 (3 pages) | Cited 6 times

Online Publication Date: 8 January 2008

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We have fabricated single crystal-like BiFeO3 (BFO) thin films by flux-mediated epitaxy using pulsed laser deposition (PLD). The Bi–Cu–O flux composition and its thickness were optimized using composition spread, thickness gradient, and temperature gradient libraries. The optimized BFO thin films grown with this technique showed larger grain size of ∼ 2 μm and higher dielectric constant in the range of 260–340 than those for standard PLD grown films. In addition, the leakage current density of the films was reduced by two orders of magnitude compared to that of standard PLD grown films.
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81.15.Fg Pulsed laser ablation deposition
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.22.Ch Permittivity (dielectric function)
68.55.aj Insulators

Behavior of stress induced leakage current in thin HfOxNy films

Ran Jiang and Zifeng Li

Appl. Phys. Lett. 92, 012919 (2008); http://dx.doi.org/10.1063/1.2831693 (3 pages) | Cited 5 times

Online Publication Date: 10 January 2008

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The behavior of stress induced leakage current (SILC) in thin HfOxNy films is investigated. Except for the H dispersive transport process, the electron trapping process is responsible for the SILC generation in HfOxNy dielectric. This trapping process is severely modulated by temperature, thickness, and stress polarity. The recovery of SILC also proves the influence of trapping process to SILC.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
77.55.-g Dielectric thin films
73.61.Ng Insulators
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Strong magnetoelectric coupling in Tb–Fe/Pb(Zr0.52Ti0.48)O3 thin-film heterostructure prepared by low energy cluster beam deposition

Shifeng Zhao, Yujie Wu, Jian-guo Wan, XinWei Dong, Jun-ming Liu, and Guanghou Wang

Appl. Phys. Lett. 92, 012920 (2008); http://dx.doi.org/10.1063/1.2831695 (3 pages) | Cited 2 times

Online Publication Date: 10 January 2008

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The magnetoelectric Tb–Fe/Pb(Zr0.52Ti0.48)O3 thin-film heterostructure was prepared by low energy cluster beam deposition. The microstructures, ferroelectric property, leakage current, and magnetization, as well as magnetoelectric effect were investigated for the heterostructure. It is shown that the thin-film heterostructure displays the well-defined microstructure with clear interface. The heterostructure not only exhibits good ferromagnetic and ferroelectric properties, but also possesses strong magnetoelectric effect. The present work provides an ideal avenue to prepare magnetoelectric composite films and facilitates their applications on the microelectromechanical system devices.
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75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.80.+q Magnetomechanical effects, magnetostriction
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Spin cast ferroelectric beta poly(vinylidene fluoride) thin films via rapid thermal annealing

Seok Ju Kang, Youn Jung Park, Jinwoo Sung, Pil Sung Jo, Cheolmin Park, Kap Jin Kim, and Beong Ok Cho

Appl. Phys. Lett. 92, 012921 (2008); http://dx.doi.org/10.1063/1.2830701 (3 pages) | Cited 17 times

Online Publication Date: 11 January 2008

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We describe a method of fabricating ferroelectric beta-type poly(vinylidene fluoride) (PVDF) thin films on Au substrate by the humidity controlled spin casting combined with rapid thermal treatment. Our method produces thin uniform ferroelectric PVDF film with ordered beta crystals consisting of characteristic needlelike microdomains. A capacitor with a 160 nm thick ferroelectric PVDF film exhibits the remanent polarization and coercive voltage of ∼ 7.0 μC/cm2 and 8 V, respectively, with the temperature stability of up to 160 °C. A ferroelectric field effect transistor also shows a drain current bistablility of 100 at zero gate voltage with ±20 V gate voltage sweep.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
81.40.Gh Other heat and thermomechanical treatments
77.22.Ej Polarization and depolarization
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Change in band alignment of HfO2 films with annealing treatments

C. J. Yim, D.-H. Ko, M. H. Jang, K. B. Chung, M.-H. Cho, and H. T. Jeon

Appl. Phys. Lett. 92, 012922 (2008); http://dx.doi.org/10.1063/1.2826270 (3 pages) | Cited 11 times

Online Publication Date: 11 January 2008

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Energy band alignment of a nitrided HfO2 film and dependence of the band gap (Eg) on annealing treatments with nitrogen plasma and ambient gases (N2 and O2) were studied by reflection electron energy loss spectra and x-ray photoelectron spectroscopy. We also investigated the nitrogen content in the film and its influence on the band alignment using medium energy ion scattering. The nitrogen incorporated into the HfO2 film by directed nitrogen plasma treatment significantly decreased the band gap and band offsets, i.e., the incorporated N in the film decreased both conduction and valance band offsets. The nitrogen content in depth direction was dependent on the postannealing conditions using O2 or N2.
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71.20.Ps Other inorganic compounds
77.55.-g Dielectric thin films
81.40.Gh Other heat and thermomechanical treatments
79.20.Uv Electron energy loss spectroscopy
79.60.Dp Adsorbed layers and thin films

Small torsional piezoelectric fiber actuators with helical electrodes

C. L. Pan, Z. H. Feng, Y. T. Ma, and Y. B. Liu

Appl. Phys. Lett. 92, 012923 (2008); http://dx.doi.org/10.1063/1.2830009 (3 pages) | Cited 1 time

Online Publication Date: 11 January 2008

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Small piezoelectric fibers wound with helical electrodes on their outer surface will produce torsional displacement. A piece of piezoelectric tube with an outer diameter of 1 mm, a wall thickness of 0.1 mm, and an effective axial length of 40 mm was used as a prototype actuator’s body, while two pieces of copper wires of 40 μm diameter were used as the electrodes. After poled with 2 kV/mm electric field strength, the prototype actuator produces 1.7° torsional angle when it was driven from −500 to 500 V. A resonant frequency as high as 10 kHz was observed on this actuator.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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