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23 Mar 2009

Volume 94, Issue 12, Articles (12xxxx)

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Appl. Phys. Lett. 94, 122502 (2009); http://dx.doi.org/10.1063/1.3100783 (3 pages)

Junhua Wang, Yisheng Shi, Juexian Cao, and Ruqian Wu
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Charge-transition levels of oxygen vacancy as the origin of device instability in HfO2 gate stacks through quasiparticle energy calculations

Eun-Ae Choi and K. J. Chang

Appl. Phys. Lett. 94, 122901 (2009); http://dx.doi.org/10.1063/1.3106643 (3 pages) | Cited 17 times

Online Publication Date: 23 March 2009

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We perform quasiparticle energy calculations to study the charge-transition levels of oxygen vacancy (VO) in HfO2. The negative-U property of VO can explain flat band voltage shifts and threshold voltage (Vth) instability in hafnium based devices. In p+ Si gate electrode, the Fermi level pinning varies by up to 0.55 eV, in good agreement with the measured values. Depending on gate bias, VO traps electrons or holes from the Si channel, causing the Vth instability. It is suggested that short time-scale charge trapping/detrapping is due to metastable VO−1 centers, whereas stable VO−2 centers dominate long time-scale instability.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices
61.72.jd Vacancies
61.72.jn Color centers

In situ investigation of the stability field and relaxation behavior of nanodomain structures in morphotropic Pb[Zr1−xTix]O3 under variations in electric field and temperature

Kristin A. Schönau, Michael Knapp, Mario Maglione, and Hartmut Fuess

Appl. Phys. Lett. 94, 122902 (2009); http://dx.doi.org/10.1063/1.3098073 (3 pages) | Cited 3 times

Online Publication Date: 23 March 2009

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The stability field of nanodomain structures recently discovered at the morphotropic phase boundary of undoped lead zirconate titanate [ Schönau et al., Phys. Rev. B 75, 184117 (2007) ] has been investigated with respect to temperature and electric field. Under electric field for distinct compositions, such as PbZr0.535Ti0.465O3, the starting domain structure of tetragonal microdomains and nanodomains is reversibly alternated into rhombohedral microdomains at high voltage. We now show that this material exhibits a dielectric relaxation directly below the formation temperature of nanodomain structures, correlated either to a high domain wall density or to polar nanoregions with activation energies in the range observed for relaxor ferroelectrics.
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77.80.Dj Domain structure; hysteresis
61.46.-w Structure of nanoscale materials
77.22.Gm Dielectric loss and relaxation
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Colossal dielectric constant up to gigahertz at room temperature

S. Krohns, P. Lunkenheimer, Ch. Kant, A. V. Pronin, H. B. Brom, A. A. Nugroho, M. Diantoro, and A. Loidl

Appl. Phys. Lett. 94, 122903 (2009); http://dx.doi.org/10.1063/1.3105993 (3 pages) | Cited 24 times

Online Publication Date: 23 March 2009

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The applicability of recently discovered materials with extremely high (“colossal”) dielectric constants, required for future electronics, suffers from the fact that their dielectric constant ε′ only is huge in a limited frequency range below about 1 MHz. In the present report, we show that the dielectric properties of a charge-ordered nickelate, La15/8Sr1/8NiO4, surpass those of other materials. Especially, ε′ retains its colossal magnitude of >10 000 well into the gigahertz range.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

Temperature- and field-dependent leakage current of epitaxial YMnO3/GaN heterostructure

H. Wu, J. Yuan, T. Peng, Y. Pan, T. Han, and C. Liu

Appl. Phys. Lett. 94, 122904 (2009); http://dx.doi.org/10.1063/1.3106635 (3 pages) | Cited 8 times

Online Publication Date: 24 March 2009

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Epitaxial ferroelectric YMnO3 (YMO) thin films were fabricated on (0001) GaN substrates by pulsed laser deposition followed by rapid thermal annealing. The temperature and field dependence of the leakage current of YMO/GaN interface was studied in a temperature range from 150 to 300 K and for an applied voltage up to 10 V. In a low temperature region from 180 to 220 K, the YMO/GaN interface acted as a Schottky barrier with a height of 0.27 eV for a field below 1.4 MV/cm, while the leakage mechanism was governed by the Fowler–Nordheim tunneling for a field above 1.4 MV/cm. Moreover, a space-charge-limited-current behavior was observed in a high field for a temperature above 270 K, while an Ohmic behavior was observed in a low field. In comparison, the dominant leakage mechanism of In/YMO interface was an Ohmic behavior in the whole measured voltage and temperature ranges.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
81.15.Fg Pulsed laser ablation deposition
73.30.+y Surface double layers, Schottky barriers, and work functions

Systematic study on work-function-shift in metal/Hf-based high-k gate stacks

Yuki Kita, Shinichi Yoshida, Takuji Hosoi, Takayoshi Shimura, Kenji Shiraishi, Yasuo Nara, Keisaku Yamada, and Heiji Watanabe

Appl. Phys. Lett. 94, 122905 (2009); http://dx.doi.org/10.1063/1.3103314 (3 pages) | Cited 1 time

Online Publication Date: 24 March 2009

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Change in the work function (WF) of the gate electrode material caused by the contact with Hf-based high-k gate dielectrics was investigated by means of the flat-band voltage (Vfb) shift in capacitance-voltage curves, and the interface dipole, which modifies the WF, was characterized by x-ray photoelectron spectroscopy. We observed a negative Vfb shift and corresponding interface dipole, which suggest the formation of oxygen vacancy (VO) in the Hf-based oxides. In contrast, we observed an opposite (positive) Vfb shift and interface dipole when Au electrodes were formed on cleaned Hf-based dielectrics. This indicates that Au–Hf bond hybridization at the Au/HfSiON interface also causes effective WF modulation, as theoretically predicted by Shiraishi et al. ( Tech. - Dig. Int. Electron Devices Meet. 2005, 43 ).
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.jd Vacancies

Ultralow dielectric losses in pyrochlore films of the PbO–MgO–Nb2O5–TiO2 system

X. H. Zhu, E. Defaÿ, A. Suhm, E. Fribourg-blanc, and M. Aïd

Appl. Phys. Lett. 94, 122906 (2009); http://dx.doi.org/10.1063/1.3106107 (3 pages) | Cited 5 times

Online Publication Date: 25 March 2009

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(1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMNT) (with x = 0.1) thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. A well-crystallized pyrochlore phase structure, which started to nucleate and grow at 450–500 °C, was formed in the PMNT thin films. These pyrochlore-structured PMNT thin films show ultralow dielectric losses with a typical loss tangent as low as 0.001, accompanied by a relatively high dielectric constant (εr = 176). Such an extremely low dielectric loss, having never been obtained in thin films of perovskite PMNT, is probably ascribed to the specific structural feature of pyrochlore phase, chemically different from its perovskite counterpart, and ascribed to the avoidance of the polar domain-related losses.
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77.55.-g Dielectric thin films
77.22.Gm Dielectric loss and relaxation
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments
77.22.Ch Permittivity (dielectric function)

Metal-oxide-semiconductor capacitors with erbium oxide dielectrics on In0.53Ga0.47As channels

Yoontae Hwang, Mark A. Wistey, Joël Cagnon, Roman Engel-Herbert, and Susanne Stemmer

Appl. Phys. Lett. 94, 122907 (2009); http://dx.doi.org/10.1063/1.3106618 (3 pages) | Cited 5 times

Online Publication Date: 26 March 2009

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Erbium oxide dielectrics with a thickness of ∼ 6 nm were fabricated in situ on In0.53Ga0.47As channels. Leakage current and capacitance densities were characterized as a function of applied voltage using metal-oxide-semiconductor capacitors with two different top electrode materials, Pt and Al. Leakage current densities were less than 10−3 A/cm2 at gate voltages up to ±2 V. The capacitance densities were lower with the Al electrode, which was attributed to a low-permittivity aluminum oxide layer at the electrode interface. The capacitors with the Pt electrode showed a pronounced increase in the capacitance in the depletion region at frequencies as high as 1 MHz, which was not observed for the Al electrode. Possible origins of the differences in the capacitance-voltage characteristics with Pt and Al electrodes are discussed.
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84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films

Domain growth dynamics in single-domain-like BiFeO3 thin films

Y. C. Chen (陳宜君), Q. R. Lin (林其叡), and Y. H. Chu (朱英豪)

Appl. Phys. Lett. 94, 122908 (2009); http://dx.doi.org/10.1063/1.3109779 (3 pages) | Cited 12 times

Online Publication Date: 26 March 2009

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We present a quantitative study of 180° domain wall motion in epitaxial BiFeO3 (111) films, which can be treated as a nearly ideal single-domain environment. The domains were dynamically written by applying voltage pulses and examined by the piezoresponse force microscope technique. A transition of domain growth behaviors from the activated type to the nonactivated type was observed when increasing the pulse voltages. The obtained activation field was close to the ideally thermodynamic switching field of BiFeO3. The asymmetry of activated fields showed the preference of the downward polarization in the BiFeO3/SrRuO3 films.
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75.80.+q Magnetomechanical effects, magnetostriction
75.70.Kw Domain structure (including magnetic bubbles and vortices)
65.40.G- Other thermodynamical quantities
77.80.Dj Domain structure; hysteresis
75.50.Ee Antiferromagnetics

High piezoelectricity of Pb(Zr,Ti)O3-based ternary compound thin films on silicon substrates

Tao Zhang, Kiyotaka Wasa, Shu-yi Zhang, Zhao-jiang Chen, Feng-mei Zhou, Zhong-ning Zhang, and Yue-tao Yang

Appl. Phys. Lett. 94, 122909 (2009); http://dx.doi.org/10.1063/1.3103553 (3 pages) | Cited 3 times

Online Publication Date: 27 March 2009

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Pb(Zr,Ti)O3 (PZT)-based ternary compound thin films, 0.06PMnN-0.94PZT(50/50) (PMnN-PZT), are deposited on Si-based heterostructures by rf magnetron sputtering system. The intrinsic PZT(50/50) thin films are also deposited on the same kind of substrates for comparison. The PMnN-PZT thin films show the similar polycrystalline structures as those of PZT with highly (111) oriented perovskite phase. The PMnN-PZT thin films show excellent piezoelectricity and ferroelectricity which are distinctly better than those of PZT thin films prepared with the same deposition conditions. Besides, the cantilevers of PMnN-PZT thin films on the heterostructure substrates also exhibit higher sensitivities than the PZT thin film cantilevers.
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77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects
77.80.-e Ferroelectricity and antiferroelectricity
81.15.Cd Deposition by sputtering
68.55.aj Insulators
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