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22 Oct 2012

Volume 101, Issue 17, Articles (17xxxx)

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Appl. Phys. Lett. 101, 171101 (2012); http://dx.doi.org/10.1063/1.4758996 (4 pages)

Wolfram H. P. Pernice and Harish Bhaskaran
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Poole-Frenkel emission in epitaxial nickel oxide on AlGaN/GaN heterostructures

Patrick Fiorenza, Giuseppe Greco, Filippo Giannazzo, Raffaella Lo Nigro, and Fabrizio Roccaforte

Appl. Phys. Lett. 101, 172901 (2012); http://dx.doi.org/10.1063/1.4761961 (4 pages) | Cited 1 time

Online Publication Date: 22 October 2012

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In this letter, the conduction mechanism through epitaxial nickel oxide (NiO) dielectric films grown by metal-organic chemical vapor deposition on AlGaN/GaN heterostructures was investigated. In particular, macroscopic current-voltage measurements carried out at different temperatures allowed to demonstrate that Poole-Frenkel (PF) mechanism rules the conduction through the dielectric layer, with an emission barrier of 0.2 eV. Conductive atomic force microscopic measurements were carried out to directly image the presence of preferential current spots on the NiO surface, which have been correlated to the defects responsible for the PF emission.
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73.50.Fq High-field and nonlinear effects
68.55.aj Insulators
77.84.Lf Composite materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Method for investigating threshold field of charge injection at electrode/dielectric interfaces by space charge observation

Zhenlian An, Jun Cang, Xuan Chen, and Yaqiang Liu

Appl. Phys. Lett. 101, 172902 (2012); http://dx.doi.org/10.1063/1.4757985 (4 pages)

Online Publication Date: 22 October 2012

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We propose a dielectric sample model to investigate the threshold field for charge injection at electrode/dielectric interfaces by space charge observation. The model sample consists of a dielectric layer and two thin charge blocking layers, respectively, placed at the inside and one side of the dielectric layer. The method has been applied to investigate the threshold field for charge injection from Al, Au, or semiconductive electrode into polyethylene. Experimental results show that charge injection occurs so long as the interface electric field is nonzero, i.e., there is no indication of a threshold field for the charge injection.
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73.40.Ns Metal-nonmetal contacts
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Jp Dielectric breakdown and space-charge effects

High-resolution structural studies and covalent bond interactions in BiFeO3-PbTiO3 compounds: The role of ferroism

L. F. Cotica, V. F. Freitas, I. B. Catellani, I. A. Santos, D. Garcia, and J. A. Eiras

Appl. Phys. Lett. 101, 172903 (2012); http://dx.doi.org/10.1063/1.4761989 (4 pages) | Cited 1 time

Online Publication Date: 23 October 2012

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The origin of enhanced ferroism in La-modified BiFeO3-PbTiO3 compounds is investigated by examining chemical bonding in high-resolution structural measurements. It is shown that structural modifications in the perovskite A-site, such as absent or inactive lone-pair ions, lead to reduced covalence in A-O bonds and increased covalence in B-O bonds for the tetragonal phase. This change in bond character results in a structural accommodation that favors the rhombohedral over the tetragonal phase, which also enhances the ferroic properties. These observations highlight the influence of modifiers on BiFeO3-PbTiO3 bonds and phase stabilization mechanisms.
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77.80.-e Ferroelectricity and antiferroelectricity
75.85.+t Magnetoelectric effects, multiferroics
77.65.-j Piezoelectricity and electromechanical effects
61.50.Lt Crystal binding; cohesive energy
61.66.Fn Inorganic compounds

A method to observe fast dynamic space charge in thin dielectric films

Feihu Zheng, Chen Lin, Chuandong Liu, Zhenlian An, Qingquan Lei, and Yewen Zhang

Appl. Phys. Lett. 101, 172904 (2012); http://dx.doi.org/10.1063/1.4763473 (4 pages) | Cited 1 time

Online Publication Date: 23 October 2012

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A method is proposed to observe the fast dynamic space charge in thin dielectric film within hundreds of nanoseconds. The method is based on measuring the transient current when a polarized sample is short-circuited. The transient short-circuit current shows damped oscillating feature. For polarized dielectric films, the initial period of damped oscillating current is partly determined by the applied electric field intensity and then the subsequent periods rapidly decrease with the oscillating cycles. The phenomena were demonstrated to be due to space charge formation and fast discharge procedure of space charge by stepwise heat treatment based experiments.
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77.22.Jp Dielectric breakdown and space-charge effects
77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization
81.40.Gh Other heat and thermomechanical treatments
73.61.Ph Polymers; organic compounds

Magneto-optical Kerr effect investigation on magnetoelectric coupling in ferromagnetic/antiferroelectric multilayer thin film structures

Meysam Sharifzadeh Mirshekarloo, Nikolai Yakovlev, Meng Fei Wong, Kui Yao, Thirumany Sritharan, and Charanjit Singh Bhatia

Appl. Phys. Lett. 101, 172905 (2012); http://dx.doi.org/10.1063/1.4764023 (4 pages)

Online Publication Date: 23 October 2012

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Magnetoelectric (ME) membranes comprising soft ferromagnetic Ni and antiferroelectric (AFE) (Pb,La)(Zr,Sn,Ti)O3 (PLZST) layers were proposed and fabricated through a bulk micro-machining process on silicon wafers. An AC-mode magneto-optical Kerr effect technique was proposed to examine the magnetoelectric coupling in the multilayer membranes, in which the electric field-induced magnetization rotation was analyzed for understanding the underlying coupling mechanisms. The AFE to ferroelectric phase transformation of PLZST induced a rotation of magnetization of about 0.5° in Ni, persuaded by strain-induced anisotropy of about −0.5 kJ/m3.
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78.20.Ls Magneto-optical effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
77.80.B- Phase transitions and Curie point
75.50.Cc Other ferromagnetic metals and alloys

Coaction and competition between the ferroelectric field effect and the strain effect in Pr0.5Ca0.5MnO3 film/0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 crystal heterostructures

Q. X. Zhu, W. Wang, S. W. Yang, X. M. Li, Y. Wang, H.-U. Habermeier, H. S. Luo, H. L. W. Chan, X. G. Li, and R. K. Zheng

Appl. Phys. Lett. 101, 172906 (2012); http://dx.doi.org/10.1063/1.4761948 (5 pages)

Online Publication Date: 24 October 2012

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The coaction and competition between the ferroelectric field effect and the strain effect in Pr0.5Ca0.5MnO3 (PCMO) film/0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 crystal heterostructures were studied. Based on different types of resistance-electric field hysteresis loops at various temperatures, it is clearly identified that the strain effect dominates over the ferroelectric field effect for temperature T above the charge-ordering temperature TCO of PCMO. With the strong localization of charge carriers for T < TCO, the ferroelectric field effect strongly competes with the strain effect and finally dominates over the latter for T < 0.8TCO. Moreover, the poling-induced strain effect is considerably enhanced by a magnetic field, demonstrating the important role of the phase separation in understanding the strain effect in such heterostructures.
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77.55.F- High-permittivity capacitive films
77.80.-e Ferroelectricity and antiferroelectricity
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.66.Fn Inorganic compounds
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Control of Schottky barrier heights by inserting thin dielectric layers

L. Lin, H. Li, and J. Robertson

Appl. Phys. Lett. 101, 172907 (2012); http://dx.doi.org/10.1063/1.4764521 (4 pages)

Online Publication Date: 25 October 2012

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The insertion of ultra-thin dielectric layers to lower n-type Schottky barrier heights is shown to partly involve the creation of a net interfacial dipole as well as unpinning of the Fermi level by suppression of metal-induced gap states. The existence of a net dipole requires a lack of cancellation of dipoles at the two interfaces. This requires a different metal(Ge)-O bond density at the two interfaces, in general requiring differing oxygen chemical potentials. This would need the inserted dielectric to be a diffusion barrier, not just able to create dipoles, favoring the use of Al2O3-based or nitrided dielectrics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
77.55.-g Dielectric thin films
71.20.Ps Other inorganic compounds

Very high remnant polarization and phase-change electromechanical response of BiFeO3-PbTiO3 at the multiferroic morphotropic phase boundary

H. Amorín, C. Correas, P. Ramos, T. Hungría, A. Castro, and M. Algueró

Appl. Phys. Lett. 101, 172908 (2012); http://dx.doi.org/10.1063/1.4764537 (5 pages)

Online Publication Date: 25 October 2012

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We have investigated the occurrence of phase-change functional responses in the BiFeO3-PbTiO3 perovskite solid solution, analogous to those anticipated by a recent first-principles study of BiFeO3-BiCoO3. Like the former system, BiFeO3-PbTiO3 shows a morphotropic phase boundary (MPB) between multiferroic polymorphs of rhombohedral and tetragonal symmetries. MPB BiFeO3-PbTiO3 is a high temperature ferroelectric with the phase transition around 900 K, and a room temperature square-shape hysteresis loop with remnant polarization as high as 62 μC cm−2. Strain under the electric field was studied, and a phase-change response was found. Analogous magnetoelectric effects are expected from the multiferroic nature of this MPB.
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77.22.Ej Polarization and depolarization
77.65.-j Piezoelectricity and electromechanical effects
77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)

Cost-effective and high frequency surface acoustic wave filters on ZnO:Fe/Si for low-loss and wideband application

J. T. Luo, F. Pan, P. Fan, F. Zeng, D. P. Zhang, Z. H. Zheng, and G. X. Liang

Appl. Phys. Lett. 101, 172909 (2012); http://dx.doi.org/10.1063/1.4764540 (3 pages) | Cited 2 times

Online Publication Date: 25 October 2012

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ZnO:Fe films with various piezoelectric coefficient d33 were employed to fabricate high frequency surface acoustic wave (SAW) filters on Si by conventional photolithography technology. Comparing with the SAW filters on undoped ZnO films, the electromechanical coupling factor and bandwidth, respectively, increases 75.7% and 14.8%, while the insertion loss decreases 20.3% when using Zn0.988Fe0.012O films with a d33 of ∼127 pC/N. Through annealing demonstration, d33 is considered as the intrinsic factor determining the SAW properties of filters, and the properties are improved by O2 annealing. ZnO:Fe films with enhanced d33 is promising for high frequency, low-loss, and wideband SAW applications.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.55.hf ZnO
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
84.30.Vn Filters

Scaling of equivalent oxide thickness of atomic layer deposited HfO2 film using RuO2 electrodes suppressing the dielectric dead-layer effect

Hyo Kyeom Kim, Il-Hyuk Yu, Jae Ho Lee, Tae Joo Park, and Cheol Seong Hwang

Appl. Phys. Lett. 101, 172910 (2012); http://dx.doi.org/10.1063/1.4764541 (5 pages) | Cited 1 time

Online Publication Date: 25 October 2012

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The influences of RuO2 metal gate on the dielectric performance of high-k HfO2 film on Si substrate were examined. The equivalent oxide thickness (EOT) of HfO2 film can be scaled down by ∼0.5 nm in the EOT range from 0.8 to 2.5 nm compared with the standard Pt gate case. This was attributed to the suppression of the dielectric dead-layer effect at the HfO2/RuO2 interface due to the possible ionic polarization of RuO2 within the screening length of the electrode. The estimated work function of RuO2 on HfO2 is ∼5.0 eV suggesting the appropriateness of RuO2 for p-transistor.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
77.55.D- High-permittivity gate dielectric films
73.30.+y Surface double layers, Schottky barriers, and work functions
73.61.Ng Insulators
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