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30 Jul 2001

Volume 79, Issue 5, pp. 557-700

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Low driving voltages and memory effect in organic thin-film transistors with a ferroelectric gate insulator

G. Velu, C. Legrand, O. Tharaud, A. Chapoton, D. Remiens, and G. Horowitz

Appl. Phys. Lett. 79, 659 (2001); http://dx.doi.org/10.1063/1.1379059 (3 pages) | Cited 43 times

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In this letter, two organic thin-film transistors with SiO2 and ferroelectric PbZrTiO3 (PZT) gate insulator are compared. The fabrication of the devices is described and their electrical properties estimated. The PZT-based devices show better performance: Low driving voltage, high Ion/Ioff ratio, etc. Moreover, a memory effect is reported in correlation with ferroelectric properties of PZT thin films. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
73.61.Ph Polymers; organic compounds

Dielectric relaxation in Ba-based layered perovskites

A. L. Kholkin, M. Avdeev, M. E. V. Costa, J. L. Baptista, and S. N. Dorogovtsev

Appl. Phys. Lett. 79, 662 (2001); http://dx.doi.org/10.1063/1.1386616 (3 pages) | Cited 47 times

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Ferroelectric materials with Bi-layered structure such as SrBi2Ta2O9 and SrBi2Nb2O9 are now intensively investigated in view of their applications in nonvolatile computer memories and high-temperature piezoelectric transducers. When Sr2+ is substituted with Ba2+, a significant disorder is induced and the material exhibits broadening of the phase transition. Such broadening is essential for applications since it allows achieving smooth temperature characteristics while maintaining high dielectric and piezoelectric properties. In this work, stoichiometric dense BaBi2Nb2O9 (BBN) ceramics are sintered using a mixed oxide route. Dielectric and ferroelectric properties are investigated in a broad range of temperatures and frequencies. Strong dispersion of the complex relative dielectric permittivity is observed including typical relaxor features such as shift of the permittivity maximum with frequency and broadening of the relaxation time spectrum with decreasing temperature. The dielectric relaxation obeys the Vögel–Fulcher relationship with anomalously low freezing temperature (Tf ≈ 100 K), which is much lower than the permittivity maximum in the radio-frequency range. Polarization hysteresis loops testify linear properties of BBN at all temperatures above Tf. The properties of BBN ceramics are compared to conventional relaxor systems such as Pb(Mg, Nb)O3 and (Pb, La)(Zr, Ti)O3. © 2001 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis

Low-temperature formation of silicon nitride gate dielectrics by atomic-layer deposition

Anri Nakajima, Takashi Yoshimoto, Toshirou Kidera, and Shin Yokoyama

Appl. Phys. Lett. 79, 665 (2001); http://dx.doi.org/10.1063/1.1388026 (3 pages) | Cited 21 times

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Thin (equivalent oxide thickness Teq of 2.4 nm) silicon nitride layers were deposited on Si substrates by an atomic-layer-deposition (ALD) technique at low temperatures (<550 °C). The interface state density at the ALD silicon nitride/Si-substrate interface was almost the same as that of the gate SiO2. No hysteresis was observed in the gate capacitance–gate voltage characteristics. The gate leakage current was the level comparable with that through SiO2 of the same Teq. The conduction mechanism of the leakage current was investigated and was found to be the direct tunneling. The ALD technique allows us to fabricate an extremely thin, very uniform silicon nitride layer with atomic-scale control for the near-future gate dielectrics. © 2001 American Institute of Physics.
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68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.20.At Surface states, band structure, electron density of states

Electrical and pyroelectric properties of in-plane polarized lead lanthanum titanate thin film

Z. T. Song, N. Chong, H. L. W. Chan, and C. L. Choy

Appl. Phys. Lett. 79, 668 (2001); http://dx.doi.org/10.1063/1.1387265 (3 pages) | Cited 8 times

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Pb0.9La0.1Ti0.975O3 (PLT10) thin films were deposited on SiO2/Si(100) substrates coated with a ZrO2 buffer layer. Studies by x-ray diffraction and scanning electron microscopy reveal that the ZrO2 film consists of both tetragonal and monoclinic phases, with the tetragonal phase being the dominant one. The PLT10 film has a perovskite structure and the grains in the film have a rather uniform size of about 50 nm. By using interdigital transducer (IDT) electrodes the in-plane electrical properties, hysteresis loop, and pyroelectric coefficient of the PLT10 film were measured. The dielectric constant and loss factor vary only slightly with frequency in the range 103–106 Hz, with the loss factor being less than 0.01 over the entire range. The leakage current density is lower than 2×10−8 A/cm2 at a bias field of 5 kV/cm. The remnant polarization and coercive field are 12.6 μC/cm2 and 9.93 kV/cm, respectively. The film exhibits a reasonably high pyroelectric coefficient (95 μC/m2 K) after it has been poled by applying 120 V ac at 0.1 Hz across the IDT electrodes. © 2001 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.70.+a Pyroelectric and electrocaloric effects
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

Epitaxial growth of Pr2O3 on Si(111) and the observation of a hexagonal to cubic phase transition during postgrowth N2 annealing

J. P. Liu, P. Zaumseil, E. Bugiel, and H. J. Osten

Appl. Phys. Lett. 79, 671 (2001); http://dx.doi.org/10.1063/1.1389509 (3 pages) | Cited 37 times

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We demonstrate the epitaxial growth of hexagonal Pr2O3(001) on Si(111), with x-ray ω-scan full width at half maximum values as low as 0.06°, which is comparable with Si substrates. We find that a phase transition takes place during the anneal of the as-grown films in N2 below the growth temperature. The annealed films display a cubic structure isomorphic to manganese oxide, (111) oriented but 180° rotated about the Si(111) surface normal. The phase transition can be due to nitrogen incorporation. © 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
64.70.K- Solid-solid transitions
68.55.-a Thin film structure and morphology
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