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26 Jan 2009

Volume 94, Issue 4, Articles (04xxxx)

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Appl. Phys. Lett. 94, 043101 (2009); http://dx.doi.org/10.1063/1.3070319 (3 pages)

Da-Yan Chen, Ming-Wang Shao, Liang Cheng, Xiu-Hua Wang, and Dorothy Duo-Duo Ma
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Band gap enhancement and electrical properties of La2O3 films doped with Y2O3 as high-k gate insulators

Yi Zhao, Koji Kita, Kentaro Kyuno, and Akira Toriumi

Appl. Phys. Lett. 94, 042901 (2009); http://dx.doi.org/10.1063/1.3075954 (3 pages) | Cited 19 times

Online Publication Date: 26 January 2009

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In this study, we prepare the well crystallized La2O3 films by doping Y2O3 with different contents (La2−xYxO3) and examine the dielectric and electrical properties of La2−xYxO3 films experimentally. It is found that the optical band gap of La2−xYxO3 film increases with the increase in Y content (x) monotonically. Furthermore, a low leakage current of about 10−5 A/cm2 (equivalent oxide thickness: 1 nm) when the gate voltage is 1 V larger than the flat band voltage, and good capacitance-voltage characteristics in Au/La2−xYxO3/Si metal-insulator-semiconductor capacitors are observed. Our results also indicate that Pt/La2−xYxO3/Au metal-insulator-metal capacitor shows a low leakage current and a small voltage dependence of the capacitance.
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73.61.Ng Insulators
77.55.-g Dielectric thin films
61.72.up Other materials
71.20.Ps Other inorganic compounds
84.32.Tt Capacitors
77.22.Ch Permittivity (dielectric function)

High-dielectric-permittivity high-elasticity three-component nanocomposites with low percolation threshold and low dielectric loss

Zhi-Min Dang, Bing Xia, Sheng-Hong Yao, Mei-Juan Jiang, Hong-Tao Song, Li-Qun Zhang, and Dan Xie

Appl. Phys. Lett. 94, 042902 (2009); http://dx.doi.org/10.1063/1.3072355 (3 pages) | Cited 9 times

Online Publication Date: 26 January 2009

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Three-component high-elasticity nanocomposites consisting of methyl vinyl silicone rubber (VMQ) and nanosized barium titanate (BT) and carbon black (CB) were fabricated. Studies on dielectric property and elastic modulus of the CB-BT/VMQ nanocomposites showed that the composites had a low percolation threshold (fc = 0.0355) due to the use of nanosized CB, and the maximum of dielectric permittivity was 960 at 103 Hz with a low dielectric loss (0.04). When the concentration of CB was close to fc, the dielectric permittivity was sensitive to the change in temperature. The present dielectric properties and excellent elasticity would satisfy the need in practical applications, especially in some fields of cable accessories and heat sensitive sensors.
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77.22.Ch Permittivity (dielectric function)
81.16.-c Methods of micro- and nanofabrication and processing
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
77.22.Gm Dielectric loss and relaxation

Polarization loss and leakage current reduction in Au/Bi3.15Nd0.85Ti3O12/Pt capacitors induced by electron radiation

Yushu Li, Ying Ma, and Yichun Zhou

Appl. Phys. Lett. 94, 042903 (2009); http://dx.doi.org/10.1063/1.3075956 (3 pages) | Cited 3 times

Online Publication Date: 27 January 2009

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Bi3.15Nd0.85Ti3O12 (BNT) thin films have been deposited on Pt/Ti/SiO2/Si substrates by a sol-gel method. Au top electrodes were formed by sputtering to fabricate capacitors with Au/BNT/Pt structure. The prepared capacitors were then subjected to 10 Mrad(Si) electron radiation. Loss in the remanent polarization and reduction in the leakage current were observed after radiation. Possible mechanisms concerning the radiation-induced changes were discussed. The polarization loss was attributed to the screening effects of trapped charge carriers, while the observed leakage currents showed a grain boundary limited conduction behavior.
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84.32.Tt Capacitors
77.55.-g Dielectric thin films
77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Passivation of oxygen vacancy states and suppression of Fermi pinning in HfO2 by La addition

D. Liu and J. Robertson

Appl. Phys. Lett. 94, 042904 (2009); http://dx.doi.org/10.1063/1.3076119 (3 pages) | Cited 8 times

Online Publication Date: 27 January 2009

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We show that group III elements such as La, Y, Sc, and Al can passivate adjacent oxygen vacancies in HfO2 and ZrO2 by shifting the vacancy gap state up into the conduction band. The shift arises from the outward relaxation of the cations around the vacancy due to its positive charge, becoming a closed shell configuration. La substitution at Hf sites in HfO2 suppresses Fermi level pinning because its holes offer a deeper sink for electrons generated by the vacancy than transfer to the metal gate.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
77.22.Ch Permittivity (dielectric function)
81.65.Rv Passivation
61.72.jd Vacancies
73.20.At Surface states, band structure, electron density of states

Morphotropic phase boundary and electrical properties of K1−xNaxNbO3 lead-free ceramics

Ye-Jing Dai, Xiao-Wen Zhang, and Ke-Pi Chen

Appl. Phys. Lett. 94, 042905 (2009); http://dx.doi.org/10.1063/1.3076105 (3 pages) | Cited 33 times

Online Publication Date: 29 January 2009

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Lead-free K1−xNaxNbO3 ceramics with x = 0.48–0.54 were prepared by a conventional solid-state reaction method to investigate the influence of the K/Na ratio on phase structures and electrical properties. The results suggest that a typical morphotropic phase boundary exists at x = 0.52–0.525, separating the monoclinic and orthorhombic phases. The sample with the composition near x = 0.52 shows the maximum values of the piezoelectric constant (d33 = 160 pC/N) and the electromechanical coupling coefficient (kt = 47%). The results provide a helpful guidance to consider the optimal ratio of K to Na for designing and developing new (K,Na)NbO3-based ceramics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.65.-j Piezoelectricity and electromechanical effects
64.70.K- Solid-solid transitions
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Switching spectroscopy piezoresponse force microscopy of polycrystalline capacitor structures

Patamas Bintachitt, Susan Trolier-McKinstry, Katyayani Seal, Stephen Jesse, and Sergei V. Kalinin

Appl. Phys. Lett. 94, 042906 (2009); http://dx.doi.org/10.1063/1.3070543 (3 pages) | Cited 18 times

Online Publication Date: 29 January 2009

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Polarization switching in polycrystalline PbZr0.52Ti0.48O3 films on Pt-coated Si substrates was studied by switching spectroscopy piezoresponse force microscopy (SSPFM). Acquisition of multiple hysteresis loops allows polarization switching parameters, including nucleation, coercive biases, and switchable response to be mapped in real space. In contrast to measurements made on the free surface, those on the metal-ferroelectric-metal capacitor structures show the evolution of correlated switching of 102–103 grain clusters with well-defined imprint and nucleation biases. The role of substrate bending on clustering and SSPFM detection mechanisms are discussed. These studies demonstrate real-space imaging of mesoscopic polarization reversal in real-world devices.
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77.80.Fm Switching phenomena
77.55.-g Dielectric thin films
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
73.40.Rw Metal-insulator-metal structures
77.80.Dj Domain structure; hysteresis

Instability of incorporated nitrogen in HfO2 films grown on strained Si0.7Ge0.3 layers

K. B. Chung, G. Lucovsky, W. J. Lee, M.-H. Cho, and Hyeongtag Jeon

Appl. Phys. Lett. 94, 042907 (2009); http://dx.doi.org/10.1063/1.3077014 (3 pages) | Cited 1 time

Online Publication Date: 29 January 2009

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The interfacial characteristics and thermal stability of nitrided HfO2 films grown on strained Si0.7Ge0.3 layers were investigated by medium energy ion scattering, high-resolution x-ray photoelectron spectroscopy, and near-edge x-ray absorption fine structure. N incorporation of HfO2 films grown on Si0.7Ge0.3 layers was strongly related to the diffusion of Si and Ge from strained Si0.7Ge0.3 layers in the interfacial region between HfO2 films and Si0.7Ge0.3 layers by the annealing treatment in NH3 ambient. The chemical states of SiOxNy and GeOxNy were formed in the interfacial region by N incorporation, and SiOxNy was dominant chemical states rather than that of GeOxNy. However, the incorporated N was not stable, which was mostly diffused out during the postnitridation annealing in a N2 ambient. The instability of incorporated N through the additional annealing treatment extensively caused the change in the structure of HfO2.
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68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Jv Interfaces; heterostructures; nanostructures
78.70.Dm X-ray absorption spectra
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Broadband dielectric spectroscopy of Ruddlesden–Popper Srn+1TinO3n+1 (n = 1,2,3) thin films

N. D. Orloff, W. Tian, C. J. Fennie, C. H. Lee, D. Gu, J. Mateu, X. X. Xi, K. M. Rabe, D. G. Schlom, I. Takeuchi, and J. C. Booth

Appl. Phys. Lett. 94, 042908 (2009); http://dx.doi.org/10.1063/1.3046792 (3 pages) | Cited 5 times

Online Publication Date: 29 January 2009

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We explore the frequency-dependent relative permittivity of Ruddlesden–Popper series Srn+1TinO3n+1 (n = 1,2,3) thin films as a function of temperature and dc electric field. Interdigitated capacitors and coplanar waveguides were used to extract the frequency response from 500 Hz to 40 GHz. At room temperature, the in-plane relative permittivities (ϵ11) obtained for Srn+1TinO3n+1 (n = 1,2,3) were 42±3, 54±3, and 77±2, respectively, and were independent of frequency. At low temperatures, ϵ11 increases and electric field tunability develops in Sr4Ti3O10.
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77.55.-g Dielectric thin films
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.22.Ch Permittivity (dielectric function)

Auxetic behavior under electrical loads in an induced ferroelectric phase

X. Tan, W. Jo, T. Granzow, J. Frederick, E. Aulbach, and J. Rödel

Appl. Phys. Lett. 94, 042909 (2009); http://dx.doi.org/10.1063/1.3076109 (3 pages) | Cited 11 times

Online Publication Date: 30 January 2009

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The longitudinal and transverse strains were measured as a function of applied electric fields in a bulk ceramic sample of Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 at room temperature. Instead of a transverse contraction, a transverse expansion was observed in the electric-field-induced ferroelectric phase after the antiferroelectric-to-ferroelectric phase transition. Therefore, an auxetic behavior was established in monolithic ferroelectric polycrystalline ceramics under electrical loads. The behavior is characterized by a negative strain ratio that is analogous to the Poisson’s ratio. The transverse expansion leads to a large hydrostatic piezoelectric coefficient dh, which suggests new applications of antiferroelectric ceramics in piezoelectric devices.
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77.80.B- Phase transitions and Curie point
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Ly Strain-induced piezoelectric fields
81.40.Lm Deformation, plasticity, and creep

Electrocaloric effect of the relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer

Bret Neese, S. G. Lu, Baojin Chu, and Q. M. Zhang

Appl. Phys. Lett. 94, 042910 (2009); http://dx.doi.org/10.1063/1.3077189 (3 pages) | Cited 34 times

Online Publication Date: 30 January 2009

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We investigate the temperature dependence of the electrocaloric effect in a relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer and show that the isothermal entropy change ΔS is proportional to the square of the electric displacement D (ΔS = −1/2βΔD2) and the coefficient β increases with temperature. This temperature dependent behavior of β is caused by the ferroelectric relaxor nature of the polymer in which the polarization response from the nanopolar regions does not generate much entropy change. Consequently, the electrocaloric effect in the relaxor ferroelectric terpolymer is smaller than that in the normal ferroelectric copolymer.
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77.70.+a Pyroelectric and electrocaloric effects
77.84.Jd Polymers; organic compounds
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.

Performance and reliability improvement of HfSiON gate dielectrics using chlorine plasma treatment

Hong Bae Park, Byongsun Ju, Chang Yong Kang, Chanro Park, Chang Seo Park, Byoung Hun Lee, Tea Wan Kim, Beom Seok Kim, and Rino Choi

Appl. Phys. Lett. 94, 042911 (2009); http://dx.doi.org/10.1063/1.3078277 (3 pages) | Cited 1 time

Online Publication Date: 30 January 2009

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The effects of chlorine plasma treatment on HfSiON gate dielectrics were investigated with respect to device performance and reliability characteristics. The chlorine plasma treatment was performed on atomic layer deposited HfSiON films to remove the residual carbon content. The optimal chlorine plasma treatment is shown to lower gate leakage current density without increasing equivalent oxide thickness of the gate stack. Secondary ion mass spectroscopy depth profiling showed that the carbon residue in HfSiON was reduced by the chlorine plasma treatment. It is demonstrated that an optimized chlorine plasma treatment improves the transistor Ion-Ioff characteristics and reduces negative-bias temperature instability.
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85.30.Tv Field effect devices
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
52.77.-j Plasma applications
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