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31 Aug 2009

Volume 95, Issue 9, Articles (09xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 091901 (2009); http://dx.doi.org/10.1063/1.3212896 (3 pages)

Noy Bassik, George M. Stern, and David H. Gracias
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Size-dependent yield stress in twinned gold nanowires mediated by site-specific surface dislocation emission

Chuang Deng and Frederic Sansoz

Appl. Phys. Lett. 95, 091914 (2009); http://dx.doi.org/10.1063/1.3222936 (3 pages) | Cited 11 times

Online Publication Date: 4 September 2009

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Large-scale molecular dynamics simulations were performed to demonstrate the synergistic effects of twin boundaries and free surfaces on dislocation emission in gold nanowires under tensile loading. It is revealed that the addition of nanoscale twins to crystalline nanowires can act to either increase or decrease their resistance to slip in tension, depending on both sample diameter and number of twins per unit length. Site-specific surface dislocation emission and image forces due to twin boundaries are used to explain the size-dependence of yield stress in twinned gold nanowires.
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62.23.Hj Nanowires
61.72.Mm Grain and twin boundaries
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)
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity

Interaction of phosphorus with dislocations in heavily phosphorus doped silicon

Y. Ohno, T. Shirakawa, T. Taishi, and I. Yonenaga

Appl. Phys. Lett. 95, 091915 (2009); http://dx.doi.org/10.1063/1.3224184 (3 pages) | Cited 5 times

Online Publication Date: 4 September 2009

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Effects of annealing at 1173 K, that is comparable to the typical temperatures for the fabrication of Si-based devices, on the dissociated dislocations in Czochralski-grown silicon crystals heavily doped with phosphorus atoms were determined. Dislocation segments with edge component are constricted. They climbed out of the slip plane toward the compression side, forming complete dislocation segments. The dissociation width of the rest segments is increased. These results suggest that phosphorus atoms segregate nearby dislocations and the high doping level at the dislocations lowers the formation energy of negatively charged vacancies.
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61.72.uf Ge and Si
81.05.Cy Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.10.Fq Growth from melts; zone melting and refining
61.72.Lk Linear defects: dislocations, disclinations
61.72.jd Vacancies
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
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Optical and electron beam studies of carrier transport in quasibulk GaN

Y. Lin, E. Flitsyian, L. Chernyak, T. Malinauskas, R. Aleksiejunas, K. Jarasiunas, W. Lim, S. J. Pearton, and K. Gartsman

Appl. Phys. Lett. 95, 092101 (2009); http://dx.doi.org/10.1063/1.3220062 (3 pages) | Cited 3 times

Online Publication Date: 31 August 2009

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Variable temperature light-induced transient grating technique combined with electron beam-induced current measurements in situ in a scanning electron microscope were employed for carrier transport studies in quasibulk hydride-vapor phase epitaxy grown undoped GaN layers. Diffusion length of carriers independently determined from both techniques was found to increase with temperature in the range from 70 to 400 K. This increase was attributed to the temperature-induced growth of carrier lifetime, as was confirmed by light-induced transient grating measurements below 300 K and by cathodoluminescence above room temperature.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
68.55.ag Semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.60.Hk Cathodoluminescence, ionoluminescence

Electroluminescence from Ge on Si substrate at room temperature

Weixuan Hu (胡炜玄), Buwen Cheng (成步文), Chunlai Xue (薛春来), Haiyun Xue (薛海韵), Shaojian Su (苏少坚), Anqi Bai (白安琪), Liping Luo (罗丽萍), Yude Yu (俞育德), and Qiming Wang (王启明)

Appl. Phys. Lett. 95, 092102 (2009); http://dx.doi.org/10.1063/1.3216577 (3 pages) | Cited 10 times

Online Publication Date: 31 August 2009

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A Ge/Si heterojunction light emitting diode with a p+-Ge/i-Ge/N+–Si structure was fabricated using the ultrahigh vacuum chemical vapor deposition technology on N+–Si substrate. The device had a good I-V rectifying behavior. Under forward bias voltage ranging from 1.1 to 2.5 V, electroluminescence around 1565 nm was observed at room temperature. The mechanism of the light emission is discussed by the radiative lifetime and the scattering rate. The results indicate that germanium is a potential candidate for silicon-based light source material.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Resistivity noise in crystalline magnetic nanowires and its implications to domain formation and kinetics

Amrita Singh, Debtosh Chowdhury, and Arindam Ghosh

Appl. Phys. Lett. 95, 092103 (2009); http://dx.doi.org/10.1063/1.3212872 (3 pages) | Cited 1 time

Online Publication Date: 31 August 2009

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We have investigated the time-dependent fluctuations in electrical resistance, or noise, in high-quality crystalline magnetic nanowires within nanoporous templates. The noise increases exponentially with increasing temperature and magnetic field, and has been analyzed in terms of domain wall depinning within the Neel–Brown framework. The frequency-dependence of noise also indicates a crossover from nondiffusive kinetics to long-range diffusion at higher temperatures, as well as a strong collective depinning, which need to be considered when implementing these nanowires in magnetoelectronic devices.
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75.60.Ch Domain walls and domain structure
75.50.Tt Fine-particle systems; nanocrystalline materials
72.70.+m Noise processes and phenomena
66.30.Pa Diffusion in nanoscale solids
61.43.Gt Powders, porous materials
73.63.-b Electronic transport in nanoscale materials and structures

Gate-controlled current switch in graphene

Kimmo Sääskilahti, Ari Harju, and Pirjo Pasanen

Appl. Phys. Lett. 95, 092104 (2009); http://dx.doi.org/10.1063/1.3216580 (3 pages) | Cited 1 time

Online Publication Date: 1 September 2009

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We numerically study cross conductances in a four-terminal all-graphene setup. We show that far away from the Dirac point, current flows along zigzag directions, giving the possibility to guide the current between terminals using a tunable pn-junction. The device operates as a gate-controlled current switch, and the electronic properties of graphene are crucial for efficient performance.
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73.63.Fg Nanotubes
85.35.Kt Nanotube devices
72.10.Bg General formulation of transport theory

Nonuniform doping distribution along silicon nanowires measured by Kelvin probe force microscopy and scanning photocurrent microscopy

E. Koren, Y. Rosenwaks, J. E. Allen, E. R. Hemesath, and L. J. Lauhon

Appl. Phys. Lett. 95, 092105 (2009); http://dx.doi.org/10.1063/1.3207887 (3 pages) | Cited 17 times

Online Publication Date: 1 September 2009

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We use Kelvin probe force microscopy and scanning photocurrent microscopy to measure the doping distribution along single phosphorous-doped silicon nanowire grown by the vapor-liquid-solid method. A nonlinear potential drop along biased silicon nanowires is detected both by measuring the surface potential directly via Kelvin probe force microscopy and by integrating the photocurrent measured by scanning photocurrent microscopy. These variations in the potential and field are further analyzed to extract the longitudinal dopant distribution along an individual silicon nanowire. The results show a very good agreement between the two methods to quantitatively detect potential, field, and doping variations within doped silicon nanowires.
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61.72.uf Ge and Si
81.16.-c Methods of micro- and nanofabrication and processing
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)
81.07.-b Nanoscale materials and structures: fabrication and characterization
72.40.+w Photoconduction and photovoltaic effects
73.63.Nm Quantum wires
81.05.Cy Elemental semiconductors
68.65.La Quantum wires (patterned in quantum wells)

Electron tunneling characteristics on La0.7Sr0.3MnO3 thin-film surfaces at high temperature

Khabiboulakh Katsiev, Bilge Yildiz, Kavaipatti Balasubramaniam, and Paul A. Salvador

Appl. Phys. Lett. 95, 092106 (2009); http://dx.doi.org/10.1063/1.3204022 (3 pages) | Cited 9 times

Online Publication Date: 1 September 2009

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We report on the electron tunneling characteristics on La0.7Sr0.3MnO3 (LSM) thin-film surfaces up to 580 °C in 10−3 mbar oxygen pressure, using scanning tunneling microscopy/spectroscopy (STM/STS). A thresholdlike drop in the tunneling current was observed at positive bias in STS, which is interpreted as a unique indicator for the activation polarization in cation-oxygen bonding on LSM cathodes. Sr-enrichment was found on the surface at high temperature using Auger electron spectroscopy, and was accompanied by a decrease in tunneling conductance in STS. This suggests that Sr-terminated surfaces are less active for electron transfer in oxygen reduction compared to Mn-terminated surfaces on LSM.
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73.61.Ng Insulators
73.20.At Surface states, band structure, electron density of states
79.20.Fv Electron impact: Auger emission
82.47.Ed Solid-oxide fuel cells (SOFC)
77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films
73.40.Gk Tunneling

Optical injection and detection of ballistic pure spin currents in Ge

Eric J. Loren, Brian A. Ruzicka, Lalani K. Werake, Hui Zhao, Henry M. van Driel, and Arthur L. Smirl

Appl. Phys. Lett. 95, 092107 (2009); http://dx.doi.org/10.1063/1.3222869 (3 pages) | Cited 9 times

Online Publication Date: 2 September 2009

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Ballistic pure spin currents are injected into Ge at 295 K using quantum interference between one and two photon absorption processes for 1786 and 893 nm, 200 fs optical pulses. The spin currents are spatially and temporally detected using polarization- and phase-dependent differential transmission techniques with nanometer spatial and femtosecond temporal resolution. We interpret the dynamics in terms of the fast spin relaxation of the holes and intervalley transfer of electrons.
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72.20.Ht High-field and nonlinear effects
72.25.Rb Spin relaxation and scattering
72.25.Dc Spin polarized transport in semiconductors
72.80.Cw Elemental semiconductors
73.23.Ad Ballistic transport

Electrochemical growth and resistive switching of flat-surfaced and (111)-oriented Cu2O films

Sung-Oong Kang, Sahwan Hong, Jinsik Choi, Jin-Soo Kim, Inrok Hwang, Ik-Su Byun, Kyu-Sik Yun, and Bae Ho Park

Appl. Phys. Lett. 95, 092108 (2009); http://dx.doi.org/10.1063/1.3202394 (3 pages) | Cited 10 times

Online Publication Date: 2 September 2009

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Flat-surfaced and fully (111)-oriented Cu2O films were grown through a chelate-assisted electrochemical approach. Based on key roles of chelating agent, the flat surface of films controlled over the columnar-grained growth was obtainable with a root-mean-square roughness value below 3 nm. Cu2O films treated by a rapid-thermal-annealing process at 200 °C exhibited unipolar switching I-V characteristics, presenting the bistable resistance states with a high resistance ratio (Roff/Ron) over 3 orders of magnitude and considerably stable switching properties within 100 switching cycles.
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81.15.Pq Electrodeposition, electroplating
81.05.Hd Other semiconductors
68.35.bg Semiconductors
61.72.Cc Kinetics of defect formation and annealing
73.61.Le Other inorganic semiconductors

Influence of Si–N complexes on the electronic properties of GaAsN alloys

Y. Jin, Y. He, H. Cheng, R. M. Jock, T. Dannecker, M. Reason, A. M. Mintairov, C. Kurdak, J. L. Merz, and R. S. Goldman

Appl. Phys. Lett. 95, 092109 (2009); http://dx.doi.org/10.1063/1.3198207 (3 pages) | Cited 3 times

Online Publication Date: 3 September 2009

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We have investigated the influence of Si–N complexes on the electronic properties of GaAsN alloys. The presence of Si–N complexes is suggested by a decrease in carrier concentration, n, with increasing N-composition, observed in GaAsN:Si films but not in modulation-doped heterostructures. In addition, for GaAsN:Te (GaAsN:Si), n increases substantially (minimally) with annealing-T, suggesting a competition between annealing-induced Si–N complex formation and a reduced concentration of N-related traps. Since Si–N complex formation is enhanced for GaAsN:Si growth with the (2×4) reconstruction, which has limited group V sites for As–N exchange, the (Si–N)As interstitial pair is identified as the dominant Si–N complex.
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81.05.Ea III-V semiconductors
71.20.Nr Semiconductor compounds
73.61.Ey III-V semiconductors
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.jj Interstitials

Coulomb blockade behavior in an indium nitride nanowire with disordered surface states

K. Aravind, Y. W. Su, I. L. Ho, C. S. Wu, K. S. Chang-Liao, W. F. Su, K. H. Chen, L. C. Chen, and C. D. Chen

Appl. Phys. Lett. 95, 092110 (2009); http://dx.doi.org/10.1063/1.3216071 (3 pages) | Cited 2 times

Online Publication Date: 4 September 2009

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We present electron transport phenomena in a single electron transistor based on an individual indium nitride nanowire. Meticulous Coulomb oscillations are observed at low temperatures. While the device shows single period Coulomb oscillation at high temperatures or at high bias voltages, additional satellite peaks along with the main Coulomb peak appear at low temperatures and low bias voltages. The quasiperiodic structure is attributed to the mixing of dissimilar Coulomb oscillations arising from two serially coupled islands embedded inadvertently in the surface metallic states of the nanowire. The proposed model is numerically simulated with good agreement with the experimental data.
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73.63.Nm Quantum wires
73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Gv Single electron devices
73.20.At Surface states, band structure, electron density of states
73.21.Hb Quantum wires
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Enhancement in the field sensitivity of magnetoelectric laminate heterostructures

J. Das, J. Gao, Z. Xing, J. F. Li, and D. Viehland

Appl. Phys. Lett. 95, 092501 (2009); http://dx.doi.org/10.1063/1.3222914 (3 pages) | Cited 29 times

Online Publication Date: 2 September 2009

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The effect of magnetostrictive layer thickness on the magnetoelectric (ME) response and field sensitivity of Pb(Zr,Ti)O3-metglas based sandwiched ME heterostructures has been studied. Such structures hold promise for sensor applications. The increase in metglas thickness results in a significant increase in the ME response and magnetic field sensitivity. The ME coefficient and field sensitivity increase by about 1.5–1.75 and 2.7 times, respectively, for a structure with 150 μm thick six metglas layers on both sides of the Pb(Zr,Ti)O3, in comparison to a 50 μm thick two layered structure.
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75.80.+q Magnetomechanical effects, magnetostriction
61.43.Fs Glasses
77.55.-g Dielectric thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Microscopic origin of training in exchange bias system

Amitesh Paul and Stefan Mattauch

Appl. Phys. Lett. 95, 092502 (2009); http://dx.doi.org/10.1063/1.3211857 (3 pages) | Cited 14 times

Online Publication Date: 2 September 2009

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The microscopic origin of training in exchange coupled systems has been identified from our experimentally observed microscopic suppression of training. It is an interplay of uniaxial anisotropy and uncompensated spins in the antiferromagnet grains that are rotatable in polycrystalline antiferromagnetic layer similar to spin-glass-like behavior.
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75.30.Gw Magnetic anisotropy
75.50.Ee Antiferromagnetics
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Three-dimensional spin structure in exchange-biased antiferromagnetic/ferromagnetic thin films

R. Morales, M. Vélez, O. Petracic, Igor V. Roshchin, Z.-P. Li, X. Batlle, J. M. Alameda, and Ivan K. Schuller

Appl. Phys. Lett. 95, 092503 (2009); http://dx.doi.org/10.1063/1.3216055 (3 pages) | Cited 5 times

Online Publication Date: 2 September 2009

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A coexistence of lateral and in-depth domain walls in antiferromagnet/ferromagnet (AF/FM) thin films exhibiting double hysteresis loops (DHLs) is demonstrated. Comparison of single and DHLs together with local and global measurements confirms the formation of two oppositely oriented domains in the AF that imprint a lateral domain structure into the FM layer. Most significantly, the magnetization reversal mechanism within each opposite domain takes place by incoherent rotation of spring-like domain walls extending through the Ni thickness. Therefore, complex three-dimensional domain walls are created perpendicular and parallel to the AF/FM interface in exchange biased systems.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Ee Antiferromagnetics
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Jk Magnetization reversal mechanisms
71.70.Gm Exchange interactions
75.30.Et Exchange and superexchange interactions
75.70.Kw Domain structure (including magnetic bubbles and vortices)

Possible origins of the magnetoresistance gain in colossal magnetoresistive oxide La0.69Ca0.31MnO3: Structure fluctuation and pinning effect on magnetic domain walls

X. Z. Yu, Run-Wei Li, T. Asaka, K. Ishizuka, K. Kimoto, and Y. Matsui

Appl. Phys. Lett. 95, 092504 (2009); http://dx.doi.org/10.1063/1.3216589 (3 pages) | Cited 6 times

Online Publication Date: 2 September 2009

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The spatial fluctuation of the magnetic domain (MD) and charge/orbital ordering (CO/OO) structure at around the Curie temperature (TC) was directly observed in a colossal magnetoresistance (CMR) compound, La0.69Ca0.31MnO3, in which extraordinary anisotropic magnetoresistance (AMR) has also been observed. It was found that the long range MD structure collapses upon the emergence of short range CO/OO in a narrow temperature regime, which provides abundant evidence in support of a gain in magnetoresistance at around TC. Moreover, the pinning effect on the MD wall was discerned and it may contribute to the CMR as well as to the extraordinary AMR effect.
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75.47.Gk Colossal magnetoresistance
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Ds Spin waves
75.60.Ch Domain walls and domain structure
71.20.Ps Other inorganic compounds
61.72.Mm Grain and twin boundaries

Superconducting quantum interference device amplifiers with over 27 GHz of gain-bandwidth product operated in the 4–8 GHz frequency range

Lafe Spietz, Kent Irwin, and José Aumentado

Appl. Phys. Lett. 95, 092505 (2009); http://dx.doi.org/10.1063/1.3220061 (3 pages) | Cited 8 times

Online Publication Date: 3 September 2009

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We describe the performance of amplifiers in the 4–8 GHz range using direct current (dc) superconducting quantum interference devices (SQUIDs) in a lumped element configuration. We have used external impedance transformers to couple power into and out of the dc SQUIDs. By choosing appropriate values for coupling capacitors, resonator lengths and output component values, we have demonstrated useful gains in several frequency ranges with different bandwidths, showing over 27 GHz of power gain-bandwidth product. In this work, we describe our design for the 4–8 GHz range and present data demonstrating gain, bandwidth, dynamic range, and drift characteristics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.30.Le Amplifiers

Enhanced magnetic refrigeration capacity in phase separated manganites

A. L. Lima Sharma, P. A. Sharma, S. K. McCall, S.-B. Kim, and S.-W. Cheong

Appl. Phys. Lett. 95, 092506 (2009); http://dx.doi.org/10.1063/1.3204694 (3 pages) | Cited 13 times

Online Publication Date: 4 September 2009

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Multiple phase transitions and magnetic phase coexistence lead to a negative magnetocaloric effect in a wide temperature range of ∼ 10–250 K in La0.215Pr0.41Ca0.375MnO3. A large fraction of the magnetocaloric effect originates from the low temperature phase separated state, which is composed of coexisting, magnetic field dependent charge ordered, and ferromagnetic regions. While the maximum isothermal entropy change is modest, the persistence of the field-dependent phase separated state over a ∼ 240 K temperature span yields a refrigeration capacity of ∼ 3.2 J/cm3. Materials with magnetic field dependent phase separation can therefore be used to improve regenerative magnetic refrigerators.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
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Spatial variations in local switching parameters of ferroelectric random access memory capacitors

D. Wu, I. Kunishima, S. Roberts, and A. Gruverman

Appl. Phys. Lett. 95, 092901 (2009); http://dx.doi.org/10.1063/1.3192354 (3 pages) | Cited 5 times

Online Publication Date: 1 September 2009

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Spatially resolved studies of the switching behavior of micrometer scale Pb(Zr,Ti)O3 capacitors have been performed by piezoresponse force microscopy (PFM). PFM spectroscopy and bias-dependent imaging of domain patterns have been used to investigate variability in local switching parameters and address the capacitor scaling effect on switching. It was found that average coercive voltage and imprint bias are independent of capacitor size and are similar to the corresponding parameters obtained by polarization hysteresis measurements. This can be attributed to the slow switching kinetics during quasistatic PFM measurements. The obtained results demonstrate a possibility of testing the submicron capacitors in real devices.
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85.50.Gk Non-volatile ferroelectric memories
84.32.Tt Capacitors
84.30.Sk Pulse and digital circuits
77.80.Fm Switching phenomena
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization

Imprint in ferroelectric materials due to space charges: A theoretical analysis

M. B. Okatan and S. P. Alpay

Appl. Phys. Lett. 95, 092902 (2009); http://dx.doi.org/10.1063/1.3222871 (3 pages) | Cited 11 times

Online Publication Date: 1 September 2009

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Imprint is a degradation mechanism in ferroelectrics that results in the displacement of the polarization hysteresis loop along the electric field axis. We develop a model using a nonlinear thermodynamic analysis coupled with electrostatics to show that such internal voltage offsets can originate from asymmetrically distributed trapped space charges. The electrostatic interactions are established through a built-in polarization due to the space charges and the spontaneous polarization. Numerical results for Ba0.8Sr0.2TiO3 show that the maximum electric field offset does not necessarily occur due to charges trapped near the electrodes.
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77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.22.Jp Dielectric breakdown and space-charge effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

On-chip terahertz Goubau-line waveguides with integrated photoconductive emitters and mode-discriminating detectors

L. Dazhang, J. Cunningham, M. B. Byrne, S. Khanna, C. D. Wood, A. D. Burnett, S. M. Ershad, E. H. Linfield, and A. G. Davies

Appl. Phys. Lett. 95, 092903 (2009); http://dx.doi.org/10.1063/1.3216579 (3 pages) | Cited 4 times

Online Publication Date: 1 September 2009

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We have measured the picosecond time-domain response of Goubau-line waveguides, formed on quartz substrates, by integrating regions of low-temperature-grown gallium arsenide into the waveguides to act both as pulsed current emitters and detectors. Using one pair of photoconductive switches for excitation and a second pair for detection, pulsed signal propagation of a low dispersion electric field mode was demonstrated in the Goubau-lines, with the signal bandwidth extending beyond 800 GHz. Furthermore, it was demonstrated that terahertz bandstop filters can be integrated into a Goubau-line for removal of specific frequencies from the transmitted pulses.
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84.40.Az Waveguides, transmission lines, striplines
85.60.-q Optoelectronic devices

Mapping bias-induced phase stability and random fields in relaxor ferroelectrics

B. J. Rodriguez, S. Jesse, A. A. Bokov, Z.-G. Ye, and S. V. Kalinin

Appl. Phys. Lett. 95, 092904 (2009); http://dx.doi.org/10.1063/1.3222868 (3 pages) | Cited 6 times

Online Publication Date: 4 September 2009

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The spatial variability of polarization reversal behavior in the relaxor 0.9Pb(Mg1/3Nb2/3O3)–0.1PbTiO3 crystal, is revealed on the ∼ 100 nm scale using switching spectroscopy piezoresponse force microscopy. Quenched fields conjugate to polarization are found, which show mesoscopic ( ∼ 100–200 nm) spatial fluctuations around near-zero bias values. The mapping of the stability gap of the bias-induced phase and conjugate random fields is demonstrated. The origin of the observed nanoscale domains and the field-induced part of the polarization are discussed.
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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
81.07.Bc Nanocrystalline materials
77.80.B- Phase transitions and Curie point
77.80.Fm Switching phenomena

Universality in phase diagram of (K,Na)NbO3–MTiO3 solid solutions

Ruiping Wang, Hiroshi Bando, and Mitsuru Itoh

Appl. Phys. Lett. 95, 092905 (2009); http://dx.doi.org/10.1063/1.3224196 (3 pages) | Cited 9 times

Online Publication Date: 4 September 2009

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Detailed phase diagrams are necessary for improving the temperature stability of piezoelectric properties of (Na,K)NbO3-based solid solutions. We report the phase diagrams of the (1−x)Na0.5K0.5NbO3–xMTiO3 (M = Pb, Ba, Sr, Ca, and Bi0.5Li0.5) solid solutions over a broad temperature range of 10 K ≤ T ≤ ∼ 770 K. It is found that the phase diagrams show several universal characteristics: (a) Curie temperature TC-T decreases sharply at low x range; (b) the relation between TC-T and x deviates from Vegard’s law; and (c) the tetragonal-orthorhombic phase transition temperature TT-O and the orthorhombic-rhombohedral phase transition temperature TO-R are almost independent of M. We suggest that valence mismatch is the main reason for the rapid decrease in TC-T and the deviation of TC-T from Vegard’s law. It is also found that TC-T is mainly affected by the A-site cations, whereas TT-O and TO-R are mainly affected by the B-site cations.
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81.30.Dz Phase diagrams of other materials
77.65.-j Piezoelectricity and electromechanical effects
64.70.K- Solid-solid transitions
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Confinement, overflow, and emission of holes on SiGe surface with Ge dots: Heterogeneous hole redistribution and its application to virtual dot manipulation

Masashi Ishii, Sarnjeet S. Dhesi, and Bruce Hamilton

Appl. Phys. Lett. 95, 093101 (2009); http://dx.doi.org/10.1063/1.3220065 (3 pages) | Cited 1 time

Online Publication Date: 31 August 2009

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The hole confinement in Ge dots fabricated on a wetting layer in Stranski–Krastanov (S-K) growth was directed by an applied bias. At medium bias voltage, the holes overflowed from the small dots, indicating a moderate potential barrier without a notch at the boundary. The electrostatic force of the confined holes attracted excessive holes to the wetting layer. The system was energetically stabilized by the formation of a “virtual dot” in an open space enclosed by dots. At a high bias voltage, the virtual dot disappeared since the holes in the wetting layer were emitted from the surface.
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73.21.La Quantum dots
73.63.Kv Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance

Conformation-induced self-assembly of rubrene on Au(111) surface

Li Wang, Huihui Kong, Xiu Chen, Xinli Du, Feng Chen, Xiaoqing Liu, and Hongming Wang

Appl. Phys. Lett. 95, 093102 (2009); http://dx.doi.org/10.1063/1.3213563 (3 pages) | Cited 5 times

Online Publication Date: 31 August 2009

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Large -area well-ordered monolayer of rubrene has been fabricated on Au(111) surface by gradually annealing a multilayer of rubrene in vacuum. Scanning tunneling microscopy clearly demonstrates that the rubrene monolayer experiences a disorder-order transition with increase of the annealing temperature and the molecules form dimer rows with opposite directions for two neighbored rows. The π-π and π-H interactions between the molecules induced by conformation of the molecules in monolayer account for the main driving forces to form this kind of ordered layer.
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68.55.-a Thin film structure and morphology
68.65.Ac Multilayers
81.40.Gh Other heat and thermomechanical treatments
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
64.70.K- Solid-solid transitions
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