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21 May 2012

Volume 100, Issue 21, Articles (21xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 213701 (2012); http://dx.doi.org/10.1063/1.3701135 (4 pages)

Wen Lo, Ara Ghazaryan, Chien-Hsin Tso, Po-Sheng Hu, Wei-Liang Chen, Tsung-Rong Kuo, Sung-Jan Lin, Shean-Jen Chen, Chia-Chun Chen, and Chen-Yuan Dong
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Characteristics of indium incorporation in InGaN/GaN multiple quantum wells grown on a-plane and c-plane GaN

Keun-Man Song, Jong-Min Kim, Bong-Kyun Kang, Dae-Ho Yoon, S. Kang, Sang-Won Lee, and Sung-Nam Lee

Appl. Phys. Lett. 100, 212103 (2012); http://dx.doi.org/10.1063/1.4720507 (4 pages)

Online Publication Date: 21 May 2012

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We investigated the characteristics of InGaN-based multiple quantum wells (MQWs) grown on a-plane and c-plane GaN templates, which were grown by metal-organic chemical vapor deposition onto r-plane and c-plane sapphire, respectively. A shorter photoluminescence peak wavelength and peaks with larger full-width at half-maximum are observed for MQWs grown on an a-plane GaN template compared with a c-plane GaN template, despite the same growth conditions used. A growth model based on the atomic configuration of the growing surfaces is proposed to explain the difference in optical emission properties and indium incorporation between a-plane and c-plane MQWs.
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61.72.uj III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.67.De Quantum wells
81.05.Ea III-V semiconductors
82.33.Ya Chemistry of MOCVD and other vapor deposition methods

High power, continuous wave, room temperature operation of λ ∼ 3.4 μm and λ ∼ 3.55 μm InP-based quantum cascade lasers

N. Bandyopadhyay, S. Slivken, Y. Bai, and M. Razeghi

Appl. Phys. Lett. 100, 212104 (2012); http://dx.doi.org/10.1063/1.4719110 (4 pages) | Cited 8 times

Online Publication Date: 21 May 2012

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We report two highly strain-balanced InP-based AlInAs/GaInAs quantum cascade lasers emitting near 3.39 and 3.56 μm. A pulsed threshold current density of only 1.1 kA/cm2 has been achieved at room temperature for both lasers with characteristic temperatures (T0) of 166 K and 152 K, respectively. The slope efficiency is also relatively temperature insensitive with characteristic temperatures (T1) of 116 K and 191 K, respectively. Continuous wave powers of 504 mW and 576 mW are obtained at room temperature, respectively. This was accomplished without buried ridge processing.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Parity oscillations of Kondo temperature in a single molecule break junction

B. M. F. de Resende and E. Vernek

Appl. Phys. Lett. 100, 212105 (2012); http://dx.doi.org/10.1063/1.4720506 (4 pages)

Online Publication Date: 22 May 2012

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We study the Kondo temperature (TK) of a single molecule break junction. By employing a numerical renormalization group calculations we have found that TK depends dramatically upon the position of the molecule in the wire formed between the contacts. We show that TK exhibits strong oscillations when the parity of the left and/or right number of atomic sites (NL,NR) is changed. For a given set of parameters, the maximum value of TK occurs for (odd, odd) combination, while its minimum value is observed for (even, even). These oscillations are fully understood in terms of the effective hybridization function.
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85.65.+h Molecular electronic devices

Acceptor-like deep level defects in ion-implanted ZnO

L. Vines, J. Wong-Leung, C. Jagadish, V. Quemener, E. V. Monakhov, and B. G. Svensson

Appl. Phys. Lett. 100, 212106 (2012); http://dx.doi.org/10.1063/1.4720514 (4 pages)

Online Publication Date: 22 May 2012

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N-type ZnO samples have been implanted with MeV Zn+ ions at room temperature to doses between 1×108 and 2×1010cm-2, and the defect evolution has been studied by capacitance-voltage and deep level transient spectroscopy measurements. The results show a dose dependent compensation by acceptor-like defects along the implantation depth profile, and at least four ion-induced deep-level defects arise, where two levels with energy positions of 1.06 and 1.2 eV below the conduction band increase linearly with ion dose and are attributed to intrinsic defects. Moreover, a re-distribution of defects as a function of depth is observed already at temperatures below 400 K.
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71.55.Gs II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
79.10.Ca Deep-level photothermal spectroscopy
71.20.Nr Semiconductor compounds

In situ study of self-assembled GaN nanowires nucleation on Si(111) by plasma-assisted molecular beam epitaxy

K. Hestroffer, C. Leclere, V. Cantelli, C. Bougerol, H. Renevier, and B. Daudin

Appl. Phys. Lett. 100, 212107 (2012); http://dx.doi.org/10.1063/1.4721521 (5 pages) | Cited 3 times

Online Publication Date: 22 May 2012

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Nucleation of GaN nanowires grown by plasma-assisted molecular beam epitaxy is studied through a combination of two in situ tools: grazing incidence x-ray diffraction and reflection high energy electron diffraction. Growth on bare Si(111) and on AlN/Si(111) is compared. A significantly larger delay at nucleation is observed for nanowires grown on bare Si(111). The difference in the nucleation delay is correlated to a dissimilarity of chemical reactivity between Al and Ga with nitrided Si(111).
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81.16.Dn Self-assembly
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
68.55.ag Semiconductors
52.77.Dq Plasma-based ion implantation and deposition
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Transport and angular resolved photoemission measurements of the electronic properties of In2O3 bulk single crystals

V. Scherer, C. Janowitz, A. Krapf, H. Dwelk, D. Braun, and R. Manzke

Appl. Phys. Lett. 100, 212108 (2012); http://dx.doi.org/10.1063/1.4719665 (5 pages) | Cited 3 times

Online Publication Date: 22 May 2012

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High quality In2O3 single crystals of bcc structure were grown by chemical vapour transport. The temperature dependence of resistivity, Hall constant, and mobility yielded an electron density of n = 1.3 × 1019 cm−3. The transport properties showed characteristics best describable by the degenerate semiconductor model. The crystals were additionally investigated by high resolution angular resolved photoelectron spectroscopy (ARPES). Emission from the valence band and the partially filled conduction band at the Γ point yielded a direct bandgap of (2.7 ± 0.1)eV. The partially filled conduction band furthermore enabled the determination of its three dimensional Fermi surface and the effective masses m* by ARPES.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.20.Nr Semiconductor compounds
72.20.My Galvanomagnetic and other magnetotransport effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Threshold voltage shift and drain current degradation by negative bias temperature instability in Si (110) p-channel metal-oxide-semiconductor field-effect transistor

K. Ota, M. Saitoh, Y. Nakabayashi, T. Ishihara, K. Uchida, and T. Numata

Appl. Phys. Lett. 100, 212109 (2012); http://dx.doi.org/10.1063/1.4722796 (3 pages)

Online Publication Date: 23 May 2012

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Negative bias temperature instability in Si (100) and (110) p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) is systematically studied. Threshold voltage shift in (110) pMOSFETs is found to be larger than that in (100) pMOSFETs because of larger amount of the generated interface traps. On the other hand, mechanisms behind the generation of the interface traps are independent of the surface orientations. We newly found that drain current degradation in (110) pMOSFETs is severer than that in (100) pMOSFETs even when the same amount of charges is generated at the interface. This can be explained by larger mobility degradation in (110) pMOSFETs.
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85.30.Tv Field effect devices

Intrinsic origin of negative fixed charge in wet oxidation for silicon carbide

Yasuhiro Ebihara, Kenta Chokawa, Shigenori Kato, Katsumasa Kamiya, and Kenji Shiraishi

Appl. Phys. Lett. 100, 212110 (2012); http://dx.doi.org/10.1063/1.4722782 (3 pages) | Cited 1 time

Online Publication Date: 24 May 2012

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We demonstrate on the basis of first-principles calculations that the formation of carbonate-like moiety in SiO2 could be the intrinsic origin of negative fixed charge in SiC thermal oxidation. We find that two possible origins for the negative fixed charges are O-lone-pair state and a negatively charged CO3 ion in SiO2. Such CO3 ion is able to be formed as a result of the existence of residual C atoms in SiO2, which are expected to be emitted from the interface between SiC and SiO2, and the incorporation of H atoms during wet oxidation.
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81.65.Mq Oxidation

Resistive switching properties of amorphous Pr0.7Ca0.3MnO3 films grown on indium tin oxide/glass substrate using pulsed laser deposition method

Tae-Geun Seong, Kyu Bum Choi, In-Tae Seo, Joon-Ho Oh, Ji Won Moon, Kwon Hong, and Sahn Nahm

Appl. Phys. Lett. 100, 212111 (2012); http://dx.doi.org/10.1063/1.4722797 (4 pages) | Cited 1 time

Online Publication Date: 24 May 2012

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Amorphous Pr0.7Ca0.3MnO3 (APCMO) films, which were grown on indium tin oxide (ITO)/glass at room temperature (RT), were n-type materials. The APCMO/ITO/glass device exhibited an average transparency of 77% in the visible range with a maximum transparency of 84% at a wavelength of 530 nm. The Pt/APCMO/ITO device showed stable bipolar resistive switching behavior over 200 cycles that did not degrade after 105 s at RT. The resistance of the APCMO film decreased in both low- and high-resistance states with increasing device area. The resistive switching behavior of the Pt/APCMO/ITO device can be explained by the trap-charged space-charge-limited current mechanism.
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73.61.Jc Amorphous semiconductors; glasses
78.66.Jg Amorphous semiconductors; glasses
81.15.Fg Pulsed laser ablation deposition
84.30.Sk Pulse and digital circuits
72.20.Ht High-field and nonlinear effects
73.50.Fq High-field and nonlinear effects

The recovery mechanism of the light-induced instability of the amorphous InGaZnO thin film transistors

Chao-Lung Wang, Huang-Chung Cheng, Chun-Yu Wu, I-Che Lee, Yu-Ting Cheng, Po-Yu Yang, Chih-Hung Tsai, Chun-Hsiang Fang, and Chung-Chun Lee

Appl. Phys. Lett. 100, 212112 (2012); http://dx.doi.org/10.1063/1.4721517 (4 pages)

Online Publication Date: 24 May 2012

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The recovery mechanism of the light-induced instability of amorphous InGaZnO thin-film transistors was examined. Following light illumination, the bare devices displayed more dark recovery of the threshold voltage (Vth) shifts than the ones encapsulated in nitrogen ambient. This was attributed to the adsorption of more oxygen (O2) in the back channel of the bare devices. Further, much more recovery was also observed for the bare devices than the nitrogen-encapsulated ones under positive gate bias. This implied the recovery effect under gate bias could be further enhanced because the induced electrons could greatly increase the adsorption of more O2 for the bare devices.
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85.30.Tv Field effect devices

Extremely high-density GaAs quantum dots grown by droplet epitaxy

M. Jo, T. Mano, Y. Sakuma, and K. Sakoda

Appl. Phys. Lett. 100, 212113 (2012); http://dx.doi.org/10.1063/1.4721663 (3 pages) | Cited 4 times

Online Publication Date: 24 May 2012

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We report the fabrication of extremely high-density GaAs quantum dots (QDs) by droplet epitaxy. We investigated the dependence of temperature and coverage on the dot density. As a result, an areal density of 7.3 × 1011  cm−2 was achieved at a growth temperature of 30 °C by controlling the amount of Ga. The QDs showed clear luminescence even when grown at a low temperature of 30 °C.
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81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
81.05.Ea III-V semiconductors

Controlling photo-induced spectral changes in CdSe/ZnS quantum dots by tuning inter-dot energy transfer

G. V. Shcherbatyuk, P. Talbot, and S. Ghosh

Appl. Phys. Lett. 100, 212114 (2012); http://dx.doi.org/10.1063/1.4721808 (4 pages) | Cited 1 time

Online Publication Date: 24 May 2012

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We study photo-induced spectral changes in films containing two sizes of chemically synthesized CdSe/ZnS quantum dots (QDs) using static and time-resolved spectroscopies. As the concentration of the smaller (donor) QDs is varied over two orders of magnitude relative to the larger (acceptor) dots, we find that with decreasing proportion of donors, the photo-oxidation rate increases in acceptors but slows down in donors. We conclude that these differences originate from the variations in the amount of inter-dot energy transfer from donors to acceptors, and this tunability can be used to enhance the shelf-life of QD based opto-electronic and photovoltaic devices.
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78.67.Hc Quantum dots
78.47.jd Time resolved luminescence
78.40.Fy Semiconductors
78.55.Et II-VI semiconductors
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Spin-dependent Seebeck effect in non-local spin valve devices

Mikhail Erekhinsky, Fèlix Casanova, Ivan K. Schuller, and Amos Sharoni

Appl. Phys. Lett. 100, 212401 (2012); http://dx.doi.org/10.1063/1.4717752 (4 pages) | Cited 1 time

Online Publication Date: 21 May 2012

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We performed measurements of Py/Cu and Py/Ag lateral spin valves as a function of injection current direction and magnitude. Above a “critical” current, there is an unexpected dependence of spin injection on current direction. Positive currents show higher polarization of spin injection than negative. This implies that in addition to current-induced spin injection, there is a thermally induced injection from a spin-dependent Seebeck effect. A temperature gradient in the Py electrode, caused by Joule heating, is responsible for injecting excess spins into the non-magnetic channel. This effect has important consequences for understanding high-current spin-based devices, such as spin transfer torque devices.
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72.15.Jf Thermoelectric and thermomagnetic effects
75.47.-m Magnetotransport phenomena; materials for magnetotransport
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Gate-controlled linear magnetoresistance in thin Bi2Se3 sheets

B. F. Gao (高波), P. Gehring, M. Burghard, and K. Kern

Appl. Phys. Lett. 100, 212402 (2012); http://dx.doi.org/10.1063/1.4719196 (4 pages) | Cited 5 times

Online Publication Date: 21 May 2012

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We explore the emergence of linear magnetoresistance in thin Bi2Se3 sheets upon tuning the carrier density using a back gate. With increasingly negative gate voltage, a pronounced magnetoresistance of ∼100% is observed, while the associated B-field dependence changes from quadratic to linear. Concomitantly, the resistance-versus-temperature curves evolve from metallic to semiconductor-like, and increasingly strong weak anti-localization behavior is manifested. Analysis of the magnetoresistance data reveals two contributions, namely from the bulk conduction band and from a state inside the bulk gap. The latter is responsible for the linear magnetoresistance and likely represents the topologically protected surface state.
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72.20.My Galvanomagnetic and other magnetotransport effects
73.20.At Surface states, band structure, electron density of states
73.25.+i Surface conductivity and carrier phenomena

Contact resistance as a probe of near-interface ferromagnetism in GaMnAs/Cu bilayers

K. F. Eid, B. Paudel, G. Riley, D. Dahliah, X. Liu, and J. K. Furdyna

Appl. Phys. Lett. 100, 212403 (2012); http://dx.doi.org/10.1063/1.4716471 (4 pages)

Online Publication Date: 21 May 2012

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We used contact resistance measurements as a sensitive probe of near-surface magnetism in GaMnAs by studying the temperature dependence of the contact resistance at Cu/GaMnAs interfaces. The specific contact resistance (ARC) has a peak that is clearly shifted towards lower temperature than that seen in GaMnAs resistivity. This shift suggests that the magnetization in the GaMnAs film is suppressed near the Cu interface. Furthermore, we show that when a native oxide layer is present between GaMnAs and Cu, the behavior of ARC is dramatically different, due to the thicker tunnel barrier at the interface.
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75.70.Ak Magnetic properties of monolayers and thin films
75.70.Rf Surface magnetism
73.40.Cg Contact resistance, contact potential
73.40.Gk Tunneling
73.40.Ns Metal-nonmetal contacts
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetization switching of an MgO/Co/Pt layer by in-plane current injection

Can Onur Avci, Kevin Garello, Ioan Mihai Miron, Gilles Gaudin, Stéphane Auffret, Olivier Boulle, and Pietro Gambardella

Appl. Phys. Lett. 100, 212404 (2012); http://dx.doi.org/10.1063/1.4719677 (3 pages)

Online Publication Date: 21 May 2012

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We demonstrate magnetization switching of a perpendicularly magnetized MgO/Co/Pt trilayer by application of an in-plane current and a constant in-plane magnetic field of small amplitude. Switching occurs due to an effective torque generated by spin-orbit coupling intrinsic to the trilayer structure. We investigate the dependence of the critical switching current on the current pulse width, showing that magnetization reversal in the dc limit is assisted by thermal fluctuations.
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75.60.Jk Magnetization reversal mechanisms
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Tj Spin-orbit effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Spin-orbit field switching of magnetization in ferromagnetic films with perpendicular anisotropy

D. Wang

Appl. Phys. Lett. 100, 212405 (2012); http://dx.doi.org/10.1063/1.4722929 (4 pages) | Cited 1 time

Online Publication Date: 25 May 2012

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As an alternative to conventional magnetic field, the effective spin-orbit field in transition metals, derived from the Rashba field experienced by itinerant electrons confined in a spatial inversion asymmetric plane through the s-d exchange interaction, is proposed for the manipulation of magnetization. Magnetization switching in ferromagnetic thin films with perpendicular magnetocrystalline anisotropy can be achieved by current induced spin-orbit field, with small in-plane applied magnetic field. Spin-orbit field induced by current pulses as short as 10 ps can initiate ultrafast magnetization switching effectively, with experimentally achievable current densities. The whole switching process completes in about 100 ps.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.30.Gw Magnetic anisotropy
75.70.Ak Magnetic properties of monolayers and thin films
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
75.30.Et Exchange and superexchange interactions

Magnetic bit stability: Competition between domain-wall and monodomain switching

Silas Hoffman, Yaroslav Tserkovnyak, Pedram Khalili Amiri, and Kang L. Wang

Appl. Phys. Lett. 100, 212406 (2012); http://dx.doi.org/10.1063/1.4716023 (4 pages) | Cited 1 time

Online Publication Date: 25 May 2012

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We numerically study the thermal stability properties of computer memory storage realized by a magnetic ellipse. In the case of practical magnetic random-access memory devices, the bit can form a spin texture during switching events. To study the energy barrier for thermally induced switching, we develop a variational procedure to force the bit to traverse a smooth path through configuration space between the points of stability. We identify textured configurations realizing domain-wall propagation, which may have an energy barrier less than that of the corresponding monodomain model. We contrast the emergence of such micromagnetic effects in thermal versus field-induced switching.
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85.75.Bb Magnetic memory using giant magnetoresistance
85.75.Dd Magnetic memory using magnetic tunnel junctions
75.78.Jp Ultrafast magnetization dynamics and switching
75.60.Ch Domain walls and domain structure
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Fluctuation of mean free path and transition temperature induced vortex pinning in (Ba,K)Fe2As2 superconductors

S. R. Ghorbani, X. L. Wang, M. Shahbazi, S. X. Dou, and C.T. Lin

Appl. Phys. Lett. 100, 212601 (2012); http://dx.doi.org/10.1063/1.4714543 (4 pages) | Cited 1 time

Online Publication Date: 21 May 2012

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The vortex pinning mechanisms of Ba0.72K0.28Fe2As2 single crystal have been studied systematically as a function of temperature and magnetic field. The temperature dependence of the critical current density, Jc(T), was analysed within the collective pinning model at different magnetic fields. It was found that both the δl pinning mechanism, i.e., pinning associated with charge-carrier mean free path fluctuation, and the δTc pinning mechanism, which is associated with spatial fluctuations of the transition temperature, coexist in the Ba0.72K0.28Fe2As2 single crystal in fields smaller than 4 T. Their contributions are strongly temperature and magnetic field dependent. At lower temperature and B ≤ 4 T, the δl pinning is the dominant mechanism, and its contributions decrease with increasing temperature. At temperatures close to the critical temperature, however, there is evidence for δTc pinning. At magnetic fields larger than 4 T, the δl pinning mechanism is the only effect.
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74.25.fc Electric and thermal conductivity
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
74.25.Sv Critical currents
74.62.Yb Other effects
74.25.Wx Vortex pinning (includes mechanisms and flux creep)
74.72.Cj Insulating parent compounds
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Tunable magnetoelectric response of dimensionally gradient laminate composites

C.-S. Park, D. Avirovik, M. I. Bichurin, V. M. Petrov, and S. Priya

Appl. Phys. Lett. 100, 212901 (2012); http://dx.doi.org/10.1063/1.4720095 (5 pages) | Cited 1 time

Online Publication Date: 21 May 2012

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A magnetoelectric (ME) sensor exhibiting wideband behavior as a function of applied magnetic DC bias and frequency was designed by combining the dimensionally gradient piezoelectric layer with Metglas magnetostrictive layers in laminate configuration. The ME coefficient of the band in the DC magnetic range of 52–242 Oe was measured to be 3000 mV/cm Oe under the resonant condition of f = 107 kHz. The wideband in the AC magnetic field frequency range of 41–110 kHz had the ME coefficient in the vicinity of 260 mV/cm Oe under the conditions of HAC = 1 Oe and HDC = 70 Oe. This frequency-dependent ME behavior clearly showed two different states on each side of the resonance peak which could open the possibility of developing new applications such as magnetic field-controlled switches.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.55.-w Magnetic instruments and components
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Tunable electric properties of PbZrO3 films related to the coexistence of ferroelectricity and antiferroelectricity at room temperature

Yaoyang Liu, Xiaomei Lu, Yaming Jin, Song Peng, Fengzhen Huang, Yi Kan, Tingting Xu, Kangli Min, and Jinsong Zhu

Appl. Phys. Lett. 100, 212902 (2012); http://dx.doi.org/10.1063/1.4720146 (4 pages) | Cited 3 times

Online Publication Date: 21 May 2012

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Polycrystalline PbZrO3 films with a preferred orientation were fabricated via the metal-organic decomposition method. For heat-treated PbZrO3 films, the P-E hysteresis loops, dielectric spectra, and I-V curves show interesting changes with time, which strongly suggest the coexistence of antiferroelectric and ferroelectric phases at room temperature. Based on the easy transition between these two phases, the electric properties of the films become tunable. A dielectric tunability of about 50.2% below 8.2 V makes it a promising low working-voltage dielectric tunable material, and the significant current change of four orders of magnitude indicates potential application as a voltage-controlled rheostat.
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77.55.fg Pb(Zr,Ti)O3-based films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.40.Gh Other heat and thermomechanical treatments
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Dielectric relaxation and electrical conductivity in ferroelectric ceramic/polymer composites around the glass transition

A. Peláiz-Barranco

Appl. Phys. Lett. 100, 212903 (2012); http://dx.doi.org/10.1063/1.4720159 (3 pages) | Cited 1 time

Online Publication Date: 22 May 2012

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The electrical conductivity behavior of the [(Pb0.88Sm0.08)(Ti0.99Mn0.01)O3]/polyetherketoneketone ceramic/polymer composite is studied in a wide temperature and frequency ranges around the glass transition of the polymer phase (Tg). The universal relaxation law is applied to model the experimental response. The dc conductivity (σdc) and the hopping frequency (ωH) follow an Arrhenius dependence. The activation energy values for σdc are associated to oxygen migration. The contribution of the conductive processes to the dielectric relaxation is analyzed, considering the oxygen vacancies concentration in the ceramic phase. It is also considered the structural change around Tg and its influence on the dielectric relaxation.
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77.80.Jk Relaxor ferroelectrics
64.70.K- Solid-solid transitions
77.22.Gm Dielectric loss and relaxation
61.41.+e Polymers, elastomers, and plastics
61.72.jd Vacancies

Spin-charge-orbital coupling in multiferroic LuFe2O4 thin films

R. C. Rai, A. Delmont, A. Sprow, B. Cai, and M. L. Nakarmi

Appl. Phys. Lett. 100, 212904 (2012); http://dx.doi.org/10.1063/1.4720401 (4 pages) | Cited 1 time

Online Publication Date: 22 May 2012

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We report optical, electronic, and electrical properties of LuFe2O4 thin films deposited on (001) sapphire and (111) YSZ substrates by electron beam deposition. The absorption spectra of LuFe2O4 thin films contain several electronic transitions above its direct energy band gap of ∼2.18 eV at 300 K. The Fe2+ d to d on-site and O 2p to Fe 3d charge-transfer electronic transitions display a ferrimagnetic transition at ∼235 ± 5 K and the charge-ordered transition at ∼350 ± 10 K. Resistivity and the energy band gap also exhibit the two transitions, confirming a strong spin-charge-orbital coupling in the LuFe2O4 thin film.
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75.85.+t Magnetoelectric effects, multiferroics
75.50.Gg Ferrimagnetics
81.15.Dj E-beam and hot filament evaporation deposition
68.55.at Other materials
78.66.Nk Insulators
73.61.Ng Insulators

Mn-doped 0.15BiInO3-0.85PbTiO3 piezoelectric films deposited by pulsed laser deposition

Sun Young Lee, Song Won Ko, Soonil Lee, and Susan Trolier-McKinstry

Appl. Phys. Lett. 100, 212905 (2012); http://dx.doi.org/10.1063/1.4718528 (3 pages)

Online Publication Date: 22 May 2012

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Undoped, 0.5 and 1.0 mol. % Mn-doped 0.15BiInO3-0.85PbTiO3 films were grown on PbTiO3/Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Phase-pure perovskite films were obtained at a substrate temperature of 585 °C irrespective of Mn doping level. The 0.5 mol. % Mn-doped films showed a room temperature permittivity of 480 and a dielectric loss tangent of 0.015 at 100 kHz after 650 °C post-deposition annealing. The coercive field and remanent polarization were 80 kV/cm and 29 µC/cm2, respectively. The ferroelectric transition temperature of the films ranged from 535 to 585 °C. The e31,f piezoelectric coefficient was −7.1 C/m2. X-ray diffraction and phase transition temperature data showed that the Mn atoms substitute on the Ti-site as Mn3+; the resulting films have p-type conduction characteristics.
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77.65.-j Piezoelectricity and electromechanical effects
81.15.Fg Pulsed laser ablation deposition
61.72.up Other materials
77.22.Ch Permittivity (dielectric function)
77.80.B- Phase transitions and Curie point
77.22.Ej Polarization and depolarization

Photoexcitation of gigahertz longitudinal and shear acoustic waves in BiFeO3 multiferroic single crystal

P. Ruello, T. Pezeril, S. Avanesyan, G. Vaudel, V. Gusev, I. C. Infante, and B. Dkhil

Appl. Phys. Lett. 100, 212906 (2012); http://dx.doi.org/10.1063/1.4719069 (3 pages) | Cited 2 times

Online Publication Date: 25 May 2012

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Show Abstract
Using femtosecond laser pulses, coherent GHz acoustic phonons are efficiently photogenerated and photodetected in BiFeO3 (BFO) multiferroic single crystal. Due to the crystal lattice symmetry, longitudinal as well as two transverse acoustic modes are generated and detected, and the corresponding sound velocities are determined. This provides the opportunity to experimentally evaluate the elastic coefficients of the multiferroic compound BiFeO3 that have been estimated so far only through ab initio calculations. The knowledge of the elastic properties of BFO is highly desired for BFO integration in nanoelectronic devices. Moreover, our findings highlight also that BFO may be a good candidate for light-controlled coherent acoustic phonons sources.
Show PACS
62.65.+k Acoustical properties of solids
62.30.+d Mechanical and elastic waves; vibrations
75.85.+t Magnetoelectric effects, multiferroics
78.47.J- Ultrafast spectroscopy (<1 psec)
63.20.-e Phonons in crystal lattices
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
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