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5 Nov 2007

Volume 91, Issue 19, Articles (19xxxx)

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Appl. Phys. Lett. 91, 191106 (2007); http://dx.doi.org/10.1063/1.2804016 (3 pages)

A. Pikulin, N. Bityurin, G. Langer, D. Brodoceanu, and D. Bäuerle
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Orientation dependence of dielectric and ferroelectric properties of Pb(Zr0.8Ti0.2)O3/Pb(Zr0.2Ti0.8)O3 multilayered thin films

Jiagang Wu, Dingquan Xiao, Jiliang Zhu, and Jianguo Zhu

Appl. Phys. Lett. 91, 192901 (2007); http://dx.doi.org/10.1063/1.2807839 (3 pages) | Cited 8 times

Online Publication Date: 5 November 2007

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The Pb(Zr1−xTix)O3 multilayered films consisting of Pb(Zr0.8Ti0.2)O3 and Pb(Zr0.2Ti0.8)O3 layers with different orientations were deposited by radio frequency magnetron sputtering with PbOx and LaNiO3 (LNO) buffer layers. The PbOx and LNO buffer layers lead to the (001)/(100) and (101)/(110) orientations of the multilayered films, respectively. The orientation dependence of electrical properties of the multilayered films was investigated. Enhanced remnant polarization (2Pr = 79.3 μC/cm2) and dielectric constant (εr = 857) were obtained for the multilayered films with (001)/(100) orientation as compared to those of the multilayered films with other orientations. These results reveal that the orientation control is important in obtaining good electrical properties.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.65.Ac Multilayers
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)

Conduction band offset of HfO2 on GaAs

G. Seguini, M. Perego, S. Spiga, M. Fanciulli, and A. Dimoulas

Appl. Phys. Lett. 91, 192902 (2007); http://dx.doi.org/10.1063/1.2805811 (3 pages) | Cited 22 times

Online Publication Date: 5 November 2007

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A detailed analysis of the band alignment between molecular beam deposited amorphous HfO2 and GaAs is reported. The conduction band offset, measured by internal photoemission (IPE), is 1.9±0.2 eV. The valence band offset (VBO) is probed by x-ray photoelectron spectroscopy (XPS). The accurate determination of the VBO requires a careful evaluation of differential charging phenomena and consequently a proper correction of the energy scale. The measured VBO value is 2.1±0.1 eV. Since the HfO2 gap is 5.6 eV, as detected by photoconductivity analysis, the results obtained by IPE and XPS are in excellent agreement.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
79.60.Bm Clean metal, semiconductor, and insulator surfaces
73.61.Ng Insulators
73.50.Pz Photoconduction and photovoltaic effects

Metal-high-k-high-k-oxide-semiconductor capacitors and field effect transistors using Al/La2O3/Ta2O5/SiO2/Si structure for nonvolatile memory applications

Chih-Hao Cheng and Joseph Ya-Min Lee

Appl. Phys. Lett. 91, 192903 (2007); http://dx.doi.org/10.1063/1.2800821 (3 pages) | Cited 13 times

Online Publication Date: 6 November 2007

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A metal-high-k-high-k-oxide-silicon structure was fabricated for nonvolatile memory applications. Al/La2O3/Ta2O5/SiO2/Si capacitors and field effect transistors were fabricated using Ta2O5 as the charge storage layer and La2O3 as the blocking layer. The programing time of the Al/La2O3/Ta2O5/SiO2/Si transistors was characterized. With a programing pulse voltage of 6 V, a threshold voltage shift of more than 0.5 V was achieved in 10 ns. As for the retention properties, the Al/La2O3/Ta2O5/SiO2/Si transistors can keep a ΔVth window of 0.83 V for 10 yr.
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85.30.Tv Field effect devices
84.32.Tt Capacitors
84.30.Sk Pulse and digital circuits

High-resolution synchrotron x-ray diffraction study of Zr-rich compositions of Pb(ZrxTi1−x)O3 (0.525 ⩽ x ⩽ 0.60): Evidence for the absence of the rhombohedral phase

Akhilesh Kumar Singh, Dhananjai Pandey, Songhak Yoon, Sunggi Baik, and Namsoo Shin

Appl. Phys. Lett. 91, 192904 (2007); http://dx.doi.org/10.1063/1.2804008 (3 pages) | Cited 20 times

Online Publication Date: 7 November 2007

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Results of Rietveld analysis of the synchrotron x-ray diffraction data on Pb(ZrxTi1−x)O3 (PZT) for 0.525 ⩽ x ⩽ 0.60 are presented to show the absence of rhombohedral phase on the Zr-rich side of the morphotropic phase boundary. Our results reveal that the structure of PZT is monoclinic in the Cm space group for 0.525 ⩽ x ⩽ 0.60. The nature of the monoclinic distortion changes from pseudotetragonal for 0.525 ⩽ x ⩽ 0.54 to pseudo-rhombohedral for x>0.54.
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61.66.Fn Inorganic compounds
81.30.Dz Phase diagrams of other materials
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

Migration of oxygen vacancy in HfO2 and across the HfO2/SiO2 interface: A first-principles investigation

Nathalie Capron, Peter Broqvist, and Alfredo Pasquarello

Appl. Phys. Lett. 91, 192905 (2007); http://dx.doi.org/10.1063/1.2807282 (3 pages) | Cited 18 times

Online Publication Date: 7 November 2007

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Oxygen vacancy migration is studied in monoclinic HfO2 and across its interface with SiO2 through density functional calculations. In HfO2, long-range diffusion shows activation barriers of 2.4 and 0.7 eV for the neutral and doubly positively charged vacancy, respectively. In the latter case, the migration preferentially occurs along one-dimensional pathways. A HfO2/SiO2 interface model is constructed to address O vacancy migration across high-κ gate stacks. The vacancy is shown to stabilize in its neutral charge state upon entering the SiO2 layer.
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66.30.Lw Diffusion of other defects
66.30.Ny Chemical interdiffusion; diffusion barriers
77.55.-g Dielectric thin films

The improvement of retention time of metal-ferroelectric (PbZr0.53Ti0.47O3)-insulator (ZrO2)-semiconductor transistors and capacitors by leakage current reduction using surface treatment

Wen-Chieh Shih, Kun-Yung Kang, and Joseph Ya-Min Lee

Appl. Phys. Lett. 91, 192906 (2007); http://dx.doi.org/10.1063/1.2807842 (3 pages)

Online Publication Date: 7 November 2007

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Metal-ferroelectric-insulator-semiconductor transistors (MFISFETs) and capacitors with the structure of Al/Pb (Zr0.53,Ti0.47) O3/ZrO2/Si were fabricated. The wafers were pretreated with H2O2 before ZrO2 deposition and/or post-treated with HCl after ZrO2 deposition. The leakage current density at 5 V is reduced from 10−1 to 5×10−6 A/cm2. The subthreshold slope was improved to 91 mV/decade. The MFISFETs maintain a threshold voltage window of about 1.1 V after an elapsed time of 3000 s. The mobility is 267 cm2/V s. The improvements are most likely due to the reduction of interfacial layer thickness and the interface states at the ZrO2/Si interface.
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85.30.Tv Field effect devices
84.32.Tt Capacitors
81.65.-b Surface treatments

Dielectric tunability of Ba0.6Sr0.4TiO3/poly(methyl methocrylate) composites in 1-3-type structure

Feng Xiang, Hong Wang, Kecheng Li, Yuehua Chen, Minghui Zhang, Ziyuan Shen, and Xi Yao

Appl. Phys. Lett. 91, 192907 (2007); http://dx.doi.org/10.1063/1.2807845 (3 pages) | Cited 14 times

Online Publication Date: 7 November 2007

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The Ba0.6Sr0.4TiO3 (BST)/poly(methyl methacrylate) (PMMA) tunable composites in 1-3-type structure consisting of BST rods in low-permittivity PMMA matrix are fabricated by dice and fill technique. For the composite containing 41.6 vol % BST, the permittivity and the loss tangent of the composite are 1212 and 0.026 at 10 kHz, respectively, while the dielectric tunability is about 36% under the 16 kV/cm dc bias flied. The theoretical tunability and permittivity are in agreement with the experimental data. The 1-3-type BST/PMMA composites can meet the device requirement for tunable dielectrics with high dielectric tunability and low permittivity.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
81.20.-n Methods of materials synthesis and materials processing

Discontinuous temperature-dependent macroscopic strain due to ferroelastic domain switching and structural phase transitions in barium strontium titanate

Can Wang, Fernando Aguado, and Simon A. T. Redfern

Appl. Phys. Lett. 91, 192908 (2007); http://dx.doi.org/10.1063/1.2809388 (3 pages) | Cited 3 times

Online Publication Date: 8 November 2007

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Remnant strain has been measured as a function of temperature in (Ba0.8Sr0.2)TiO3 (BST) ceramic by mechanical poling in three point bending configuration. BST ceramic exhibits recoverable macroscopic strain with shape memory effect and three jumps in the temperature-dependent strain during thermal cycling under applied force. The jumps are associated with the three structural phase transitions of BST, as confirmed by the simultaneous measurements of dynamic modulus and internal friction. In addition, the orthorhombic phase of BST exhibits a significantly higher strain comparing to that in the tetragonal and rhombohedral phases. X-ray diffraction confirms that the macroscopic strain is due to ferroelastic domain switching and particularly the dominant contribution to the higher macroscopic strain at orthorhombic phase is the higher probability of non-180° domain switching rather than the variation of domain switching strain at different phases.
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77.80.Fm Switching phenomena
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Ultralow equivalent oxide thickness obtained for thin amorphous LaAlO3 layers grown on Si(001)

L. Becerra, C. Merckling, N. Baboux, C. Plossu, O. Marty, M. El-Kazzi, G. Saint-Girons, B. Vilquin, and G. Hollinger

Appl. Phys. Lett. 91, 192909 (2007); http://dx.doi.org/10.1063/1.2811956 (3 pages) | Cited 4 times

Online Publication Date: 9 November 2007

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Electron beam evaporation in a molecular beam epitaxy reactor was used to deposit, at 400 °C, amorphous LaAlO3 high-κ oxide films on p-type Si(001). X-ray photoelectron spectroscopy and transmission electron microscopy showed that the interface with Si is free of SiO2 or silicates. Electrical measurements performed on as-deposited samples reveal an equivalent oxide thickness as low as 5 Å for a film having a physical thickness of 41 Å, a leakage current of 5.6×10−2 A/cm2 at ∣Vg−VFB∣ = 1 V, and no flatband voltage shift.
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77.55.-g Dielectric thin films
81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
79.60.Bm Clean metal, semiconductor, and insulator surfaces

(Na0.5Bi0.5)0.87Pb0.13TiO3 thin films on different substrates for ferroelectric memory applications

C. H. Yang, G. D. Hu, and X. Q. Sun

Appl. Phys. Lett. 91, 192910 (2007); http://dx.doi.org/10.1063/1.2811957 (3 pages) | Cited 3 times

Online Publication Date: 9 November 2007

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(Na0.5Bi0.5)0.87Pb0.13TiO3 thin films have been prepared on Pt/Ti/SiO2/Si and Bi2Ti2O7/Si substrates using a metal organic decomposition method. The electrical measurements were conducted on metal-ferroelectric-metal or metal-ferroelectric-insulator-semiconductor capacitors. As Bi2Ti2O7 is an effective diffusion barrier, the leakage current and memory properties of (Na0.5Bi0.5)0.87Pb0.13TiO3/Bi2Ti2O7/Si are relatively improved. The polarization-electric field and capacitance-voltage measurements of (Na0.5Bi0.5)0.87Pb0.13TiO3 on Pt show good ferroelectric properties. The three phase transitions in (Na0.5Bi0.5)0.87Pb0.13TiO3 can be recognized by the change of capacitance with temperature.
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85.50.Gk Non-volatile ferroelectric memories
84.30.Sk Pulse and digital circuits
84.32.Tt Capacitors
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