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22 Jan 2001

Volume 78, Issue 4, pp. 393-559

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Magnetic susceptibility and microstructure of hydrogenated amorphous silicon measured by nuclear magnetic resonance on a single thin film

Jonathan Baugh, Daxing Han, Alfred Kleinhammes, and Yue Wu

Appl. Phys. Lett. 78, 466 (2001); http://dx.doi.org/10.1063/1.1341217 (3 pages) | Cited 12 times

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A nuclear magnetic resonance technique for precisely measuring the bulk magnetic susceptibility of micron-thick hydrogenated amorphous silicon (a-Si:H) film is introduced. The large disorder-induced diamagnetic enhancement exhibited by a-Si:H is shown to provide a sensitive bulk measurement for detecting variations in structural order in a-Si:H films. Furthermore, this approach is shown to be effective in revealing the details of microstructure in a-Si:H, including the presence of microstructural anisotropy. © 2001 American Institute of Physics.
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75.20.Ck Nonmetals
68.55.-a Thin film structure and morphology
76.60.-k Nuclear magnetic resonance and relaxation
75.70.Ak Magnetic properties of monolayers and thin films
61.43.Dq Amorphous semiconductors, metals, and alloys

Strip inverse-configuration photopyroelectric technique to measure the thermal conductivity of bulk samples

Srirang Manohar and S. Asokan

Appl. Phys. Lett. 78, 469 (2001); http://dx.doi.org/10.1063/1.1342782 (3 pages) | Cited 1 time

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The strip inverse-configuration photopyroelectric technique to measure the thermal conductivity of bulk samples of metals, semiconductors, and insulators is presented. It utilizes a narrow (500 μm wide) strip of a 9 μm thick pyroelectric sensor in an inverse configuration. A mathematical model is outlined that yields an expression for the output voltage of the pyroelectric sensor following heat dissipation into the sample, in a frequency range where the proposed measurement is possible. Experimentally, the sensor was operated in an “isothermal-voltage” mode to identify the frequency regime within which the measurement of the thermal conductivity of representative samples was possible after suitable calibration of the system. © 2001 American Institute of Physics.
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07.20.-n Thermal instruments and apparatus
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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Monolithic integration of a quantum-well infrared photodetector array with a read-out circuit

D. Mandelik, M. Schniederman, V. Umansky, and I. Bar-Joseph

Appl. Phys. Lett. 78, 472 (2001); http://dx.doi.org/10.1063/1.1340862 (3 pages) | Cited 2 times

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We demonstrate the feasibility of monolithic integration of a quantum-well infrared detector and a read-out circuit on the same GaAs/AlGaAs crystal. Charge storage capability of 2×107 electrons in a 50×50 μm2 pixel is obtained. The operation of a 5×5 test array is reported, performing all the basic functions of a practical focal plane array. © 2001 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Gz Photodetectors (including infrared and CCD detectors)
73.63.Hs Quantum wells
78.67.De Quantum wells
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Large and abrupt optical band gap variation in In-doped ZnO

Kwang Joo Kim and Young Ran Park

Appl. Phys. Lett. 78, 475 (2001); http://dx.doi.org/10.1063/1.1342042 (3 pages) | Cited 63 times

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Optical absorption properties of n-type In-doped ZnO films were investigated by spectroscopic ellipsometry for varying carrier concentration. The fundamental optical band gap (E0) edge of the compound showed a blueshift below the carrier concentration n0 = 5×1019 cm−3, which can be explained in terms of the Burstein–Moss band-filling effect. An abrupt jump of the E0 edge from blue- to redshift was observed as the carrier concentration increased beyond n0. It is interpreted as due to a merging of the donor and conduction bands of the compound near n0. The redshift increases quite linearly with the carrier concentration, reaching 600 meV for n = 1.2×1020 cm−3. Such linear increase is interpreted as mainly due to a band gap narrowing caused by impurity-induced potential fluctuations. © 2001 American Institute of Physics.
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78.66.Hf II-VI semiconductors
71.20.Nr Semiconductor compounds
73.61.Ga II-VI semiconductors
78.40.Fy Semiconductors
71.55.Gs II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Comparison of field effect transistor characteristics between space-grown and earth-grown gallium arsenide single crystal substrates

Nuo Fu Chen, Xingru Zhong, Lanying Lin, Mian Zhang, Yunsheng Wang, Xiwei Bai, and Jing Zhao

Appl. Phys. Lett. 78, 478 (2001); http://dx.doi.org/10.1063/1.1342201 (2 pages)

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Semi-insulating gallium arsenide single crystal grown in space has been used in fabricating low noise field effect transistors and analog switch integrated circuits by the direct ion-implantation technique. All key electrical properties of these transistors and integrated circuits have surpassed those made from conventional earth-grown gallium arsenide. This result shows that device-grade space-grown semiconducting single crystal has surpassed the best terrestrial counterparts. © 2001 American Institute of Physics.
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85.30.De Semiconductor-device characterization, design, and modeling
81.10.Mx Growth in microgravity environments
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
85.30.Tv Field effect devices

Direct observation of electrical charges at dislocations in GaAs by cross-sectional scanning tunneling microscopy

Ph. Ebert, C. Domke, and K. Urban

Appl. Phys. Lett. 78, 480 (2001); http://dx.doi.org/10.1063/1.1341219 (3 pages) | Cited 16 times

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We demonstrate the possibility of simultaneous determination of the type and electrical charge state of dislocations in GaAs by cross-sectional scanning tunneling microscopy (STM). The methodology is demonstrated for a dissociated perfect dislocation in highly Si-doped GaAs(110) surfaces. The STM images of the dislocation penetrating GaAs cleavage surface show that both partial dislocation cores as well as the stacking fault between the two partial dislocation cores are negatively charged. © 2001 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.Dv Composition, segregation; defects and impurities
61.72.Nn Stacking faults and other planar or extended defects

Low turn-on voltage GaAs heterojunction bipolar transistors with a pseudomorphic GaAsSb base

Tohru Oka, Tomoyoshi Mishima, and Makoto Kudo

Appl. Phys. Lett. 78, 483 (2001); http://dx.doi.org/10.1063/1.1343853 (3 pages) | Cited 10 times

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We have developed GaAs heterojunction bipolar transistors (HBTs) with low turn-on voltage by using pseudomorphic GaAsSb as the base layer. The turn-on voltage of GaAs/GaAs0.91Sb0.09 HBT is 0.10 V lower than that of InGaP/GaAs HBT. The lower turn-on voltage is attributed to the smaller band gap of the GaAsSb base layer, indicating that GaAsSb is useful material for reducing turn-on voltage of GaAs HBTs. The current gain of 20 is obtained for GaAs/GaAs0.91Sb0.09 HBT, which is larger than those of previously reported GaAs/GaAsSb HBTs owing to the pseudomorphic, fully strained GaAsSb with no misfit dislocations. The knee voltage of 0.47 V is attained at the collector current density of 5×104 A/cm2. These results indicate that GaAs/GaAsSb HBTs have a great potential for reducing operating voltage and power dissipation. © 2001 American Institute of Physics.
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85.30.Pq Bipolar transistors
81.05.Ea III-V semiconductors

Enhanced tunnel current through thin oxide due to single-defect scattering

Y. Fu, M. Willander, P. Lundgren, and E. Aderstedt

Appl. Phys. Lett. 78, 486 (2001); http://dx.doi.org/10.1063/1.1338958 (3 pages) | Cited 1 time

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We have studied the conduction current from an n-silicon substrate to n+-polycrystalline-silicon gate through an ultrathin oxide layer. Carrier transmission through the thin oxide layer is enhanced by the presence of an ionized impurity in the oxide layer. In addition to the normal direct tunnel current, the Coulomb potential of the ionized impurity provides extra conduction channels for carriers in the n-silicon substrate to transmit to the polycrystalline-silicon gate. It has been found that the ratio between the conduction current through the extra conduction channels and the direct tunnel current can be as large as 1.9. The exact value of the ratio depends on the location of the charge in the oxide layer. © 2001 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
71.55.Ht Other nonmetals
72.20.Dp General theory, scattering mechanisms

Microwave transmission through a two-dimensional, isotropic, left-handed metamaterial

R. A. Shelby, D. R. Smith, S. C. Nemat-Nasser, and S. Schultz

Appl. Phys. Lett. 78, 489 (2001); http://dx.doi.org/10.1063/1.1343489 (3 pages) | Cited 351 times

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We present experimental data, numerical simulations, and analytical transfer-matrix calculations for a two-dimensionally isotropic, left-handed metamaterial (LHM) at X-band microwave frequencies. A LHM is one that has a frequency band with simultaneously negative εeff(ω) and μeff(ω), thereby having real values of index of refraction and wave vectors, and exhibiting extended wave propagation over that band. Our physical demonstration of a two-dimensional isotropic LHM will now permit experiments to verify some of the explicit predictions of reversed electromagnetic-wave properties including negative index of refraction as analyzed by Veselago [Usp. Fiz. Nauk 92, 517 (1964), Sov. Phys. Usp. 10, 509 (1968)]. © 2001 American Institute of Physics.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation

Snapback behavior of the postbreakdown I–V characteristics in ultrathin SiO2 films

T. P. Chen, M. S. Tse, and X. Zeng

Appl. Phys. Lett. 78, 492 (2001); http://dx.doi.org/10.1063/1.1342214 (3 pages) | Cited 16 times

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With the I–V measurement technique that forced a current to an ultrathin gate oxide and measured the voltage drop, a snapback phenomenon, i.e., the gate oxide was switched from a higher-impedance state to a lower-impedance state suddenly, was observed during the postbreakdown I–V measurement. The snapback could be triggered at a very low measurement current. Single or multiple snapbacks have been observed, and it was found that the occurrence of snapback was a random event. The snapback is explained in terms of the formation of an additional percolation path due to the neutralization of negatively charged traps or the generation of neutral electron traps at certain strategic positions during the measurement. © 2001 American Institute of Physics.
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73.61.Ng Insulators
77.22.Jp Dielectric breakdown and space-charge effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Infrared multispectral detection using Si/SixGe1−x quantum well infrared photodetectors

D. Krapf, B. Adoram, J. Shappir, A. Sa’ar, S. G. Thomas, J. L. Liu, and K. L. Wang

Appl. Phys. Lett. 78, 495 (2001); http://dx.doi.org/10.1063/1.1343498 (3 pages) | Cited 10 times

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A modified p-type Si/SiGe quantum well infrared photodetector for multispectral infrared imaging applications is demonstrated. In order to improve the detector’s performances we have used a SiGe emitter and a low-temperature wet passivation process that give rise to a reduced dark current, even at relatively high bias voltages. Multispectral photoresponse at the long, mid and short wavelength infrared atmospheric windows was observed. The response peaks are assigned to the various classes of intervalence band transitions in the quantum wells and in the SiGe emitter layers. © 2001 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.21.Fg Quantum wells
81.07.St Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.65.Rv Passivation
72.40.+w Photoconduction and photovoltaic effects
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Layered chiral metallic microstructures with inductive coupling

Yuri Svirko, Nikolay Zheludev, and Michail Osipov

Appl. Phys. Lett. 78, 498 (2001); http://dx.doi.org/10.1063/1.1342210 (3 pages) | Cited 40 times

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A bilayered quasiplanar metallic microstructure, comprising an ensemble of fully metallic “molecules” with inductive coupling between two parts of the molecule, is predicted to show strong optical rotatory power. © 2001 American Institute of Physics.
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42.25.Ja Polarization
78.20.Ek Optical activity
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Interfacial capacitance effects in magnetic tunneling junctions

G. Landry, Y. Dong, J. Du, X. Xiang, and John Q. Xiao

Appl. Phys. Lett. 78, 501 (2001); http://dx.doi.org/10.1063/1.1336816 (3 pages) | Cited 18 times

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We have fabricated magnetic tunneling junctions by oxidizing a wedge-shaped aluminum layer to produce junctions with ideal oxidized as well as under and over oxidized junctions on a single wafer. By investigating the capacitance spectra, we are able to study the effects due to interface charge accumulation. The electron–electron interaction among accumulated interface charges leads to a voltage drop inside the magnetic electrodes, resulting in the measured capacitance differing from the geometric capacitance. We have extracted an interfacial capacitance of 16 μF/cm2 per interface and a screening length of 0.55 Å for FeNi electrodes. © 2001 American Institute of Physics.
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75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Enhanced initial susceptibility in small amorphous disks

Amikam Aharoni

Appl. Phys. Lett. 78, 504 (2001); http://dx.doi.org/10.1063/1.1342052 (2 pages) | Cited 3 times

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A highly enhanced initial susceptibility is predicted theoretically for thin, amorphous ferromagnetic films when they are patterned as separate disks of appropriate dimensions. The relation between the required disk radius and the film thickness is given as a function of the exchange constant and the saturation magnetization of the amorphous material. © 2001 American Institute of Physics.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions

Josephson plasma observed in underdoped (110) YBa2Cu3O7−δ films

X. G. Qiu, H. Koinuma, M. Iwasaki, T. Itoh, A. K. Sarin Kumar, M. Kawasaki, E. Saitoh, Y. Tokura, K. Takehana, G. Kido, and Y. Segawa

Appl. Phys. Lett. 78, 506 (2001); http://dx.doi.org/10.1063/1.1342208 (3 pages) | Cited 4 times

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(110) oriented YBa2Cu3O7−δ thin films have been epitaxially grown on vicinal (110)SrTiO3 substrates by pulsed-laser deposition. Films with different oxygen deficiencies were obtained by annealing under various oxygen ambient. These films have very smooth surface and with their c axis aligned in one direction in the substrate plane. Electronic transport and polarized far-infrared reflectivity measurements reveal the unique features of the c-axis charge dynamics. A c-axis far-infrared reflectivity edge associated with the Josephson plasma in the superconducting state is observed. Our results demonstrate the potential usage of (110) thin films for the investigation of intrinsic interlayer charge dynamics as well as device application of high Tc superconductors. © 2001 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.50.+r Tunneling phenomena; Josephson effects
74.25.F- Transport properties
81.15.Fg Pulsed laser ablation deposition
74.25.Gz Optical properties

Single-crystal magnetotunnel junctions

W. Wulfhekel, M. Klaua, D. Ullmann, F. Zavaliche, J. Kirschner, R. Urban, T. Monchesky, and B. Heinrich

Appl. Phys. Lett. 78, 509 (2001); http://dx.doi.org/10.1063/1.1342778 (3 pages) | Cited 66 times

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We have grown epitaxial single-crystal magnetotunnel junctions using Fe(001) substrates, MgO(001) spacers and Fe top electrodes. We have used scanning tunneling microscopy and atomic force microscopy to measure the tunneling characteristics as a function of position and demonstrated that local tunneling can be obtained such that the buried MgO can be characterized with nm resolution. Local I(V) curves revealed that most of the area had intrinsic tunneling properties corresponding to the proper MgO tunneling barrier. A small fraction of the scanned areas showed localized spikes in the tunneling current which are most likely caused by defects in the MgO. © 2001 American Institute of Physics.
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73.40.Rw Metal-insulator-metal structures
73.40.Gk Tunneling
75.45.+j Macroscopic quantum phenomena in magnetic systems
85.75.Dd Magnetic memory using magnetic tunnel junctions
68.37.Ps Atomic force microscopy (AFM)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
61.72.-y Defects and impurities in crystals; microstructure
68.35.Ct Interface structure and roughness

Atomic ordering in the LaFe0.5Mn0.5O3 solid solution film

K. Ueda, Y. Muraoka, H. Tabata, and T. Kawai

Appl. Phys. Lett. 78, 512 (2001); http://dx.doi.org/10.1063/1.1343844 (3 pages) | Cited 15 times

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LaFe0.5Mn0.5O3 solid solution films have been formed on SrTiO3 (111) substrates using a pulsed laser deposition technique and their magnetic properties have been examined. The films showed ferromagnetic (or ferromagnetic) behavior with a Curie temperature of 380 K and the saturation magnetization was estimated to be about 1.5μB per magnetic ion site (B site). The x-ray photoemission spectra indicated that this behavior was due to the partial ordering of magnetic ions (Fe and Mn ions) which is caused by the charge disproportion between Fe and Mn ions under the film formation conditions. © 2001 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
68.55.-a Thin film structure and morphology
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.-s Critical-point effects, specific heats, short-range order
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.Fg Pulsed laser ablation deposition
79.60.Dp Adsorbed layers and thin films
64.75.-g Phase equilibria

Enhanced tunnel magnetoresistance in granular nanobridges

K. Yakushiji, S. Mitani, K. Takanashi, S. Takahashi, S. Maekawa, H. Imamura, and H. Fujimori

Appl. Phys. Lett. 78, 515 (2001); http://dx.doi.org/10.1063/1.1341231 (3 pages) | Cited 50 times

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We have fabricated granular nanobridge structures consisting of electrodes separated by a nanometer-sized gap in which a thin insulating CoAlO granular film is filled, and measured the current–bias voltage characteristics in a magnetic field to investigate the spin-dependent transport. The Coulomb blockade with a clear threshold voltage (Vth) is observed at 4.2 K. Tunnel magnetoresistance (TMR) is enhanced by fabricating nanobridges. TMR shows a maximum exceeding about 30% at the voltage slightly above Vth. This enhancement is explained by the orthodox theory of single electron tunneling in ferromagnetic multiple tunnel junctions. © 2001 American Institute of Physics.
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75.47.De Giant magnetoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.23.Hk Coulomb blockade; single-electron tunneling
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Dd Nonmetallic ferromagnetic materials
75.45.+j Macroscopic quantum phenomena in magnetic systems

Control of magnetization reversal process by light illumination in ferromagnetic semiconductor heterostructure p-(In, Mn)As/GaSb

A. Oiwa, T. Słupinski, and H. Munekata

Appl. Phys. Lett. 78, 518 (2001); http://dx.doi.org/10.1063/1.1343497 (3 pages) | Cited 46 times

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The reduction in coercive force by light illumination has been found in ferromagnetic semiconductor heterostructure p-(In, Mn)As/GaSb prepared by molecular-beam epitaxy. Enhanced ferromagnetic coupling between Mn ions, arising from excess photogenerated holes, reduces the domain wall energy and changes the magnetization hysteresis characteristics. The value of coercive force returns to the original value when excess holes recombine with trapped electrons. © 2001 American Institute of Physics.
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75.60.Jk Magnetization reversal mechanisms
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
75.70.Kw Domain structure (including magnetic bubbles and vortices)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Potential phase control of chromium oxide thin films prepared by laser-initiated organometallic chemical vapor deposition

Ruihua Cheng, C. N. Borca, P. A. Dowben, Shane Stadler, and Y. U. Idzerda

Appl. Phys. Lett. 78, 521 (2001); http://dx.doi.org/10.1063/1.1343846 (3 pages) | Cited 11 times

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We have used laser-initiated chemical vapor deposition to grow the chromium oxide thin films through the oxidation of Cr(CO)6 in an oxygen environment. While both Cr2O3 and CrO2 are present in the film, the relative weight of each phase depends on the oxygen partial pressure. The Curie temperature of the film increases and approaches the bulk TC of CrO2 (397 K) as the partial oxygen pressure is increased. © 2001 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
68.55.Nq Composition and phase identification
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.-s Critical-point effects, specific heats, short-range order
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Origin of the “up,” “down” hysteresis offsets observed from polarization-graded ferroelectric materials

Whitney Fellberg, Joseph Mantese, Norman Schubring, and Adolph Micheli

Appl. Phys. Lett. 78, 524 (2001); http://dx.doi.org/10.1063/1.1342045 (3 pages) | Cited 31 times

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“Up” and “down” hysteresis offsets were observed in polarization-graded ferroelectrics. The polarization gradients were achieved by imposing temperature gradients across a bulk ferroelectric material near its Curie temperature. In the absence of temperature gradients, no hysteresis offsets were observed, ruling out extraneous sources as the cause of the aberrant behavior, thereby establishing the origin of the offsets in the class of polarization-graded ferroelectric devices. © 2001 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point

Dielectric nonlinearities in ferroelectric thin-film heterostructures

M. Tyunina, J. Levoska, S. Leppävuori, and A. Sternberg

Appl. Phys. Lett. 78, 527 (2001); http://dx.doi.org/10.1063/1.1342051 (3 pages) | Cited 10 times

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The influence of the film–electrode interface on the ac-electric field dependence of the dielectric permittivity in ferroelectric thin-film heterostructures has been studied. The dielectric nonlinearities in epitaxial thin-film heterostructures of ferroelectric PbZr0.65Ti0.35O3 and relaxor ferroelectric (PbMg1/3Nb2/3O3)0.68–(PbTiO3)0.32 were measured at subswitching fields. A dramatic difference between the dielectric nonlinearities possessed by ferroelectric films and those exhibited by the corresponding heterostructures was revealed both by model evaluations and experimental observations. In the heterostructures, due to the presence of an interface layer the dielectric nonlinearities can be considerably suppressed and their type can be changed compared to those in the films. © 2001 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.80.Fm Switching phenomena

In-plane polarization states and their instabilities in polydomain epitaxial ferroelectric thin films

V. G. Koukhar, N. A. Pertsev, and R. Waser

Appl. Phys. Lett. 78, 530 (2001); http://dx.doi.org/10.1063/1.1338960 (3 pages) | Cited 11 times

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A Landau–Ginsburg–Devonshire-type thermodynamic theory is used to describe epitaxial ferroelectric films with dense laminar domain structures, where spontaneous polarizations in both domains are oriented in the film plane. For PbTiO3 films, it is found that, at positive misfit strains, the domain patterning transforms the orthorhombic aa phase, which is stable in single-domain films, into a pseudotetragonal a1/a2/a1/a2 polydomain state. In BaTiO3 films, the latter is further replaced at low temperatures by a polydomain aa1/aa2/aa1/aa2 state. With decreasing misfit strain, both a1/a2/a1/a2 and aa1/aa2/aa1/aa2 patterns become unstable with respect to the appearance of polarization component orthogonal to film surfaces. This results in the formation of polydomain states in BaTiO3 films, which do not exist in bulk crystals. The stability ranges of various states in the misfit strain-temperature phase diagram are determined. © 2001 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis

Effects of very thin strain layers on dielectric properties of epitaxial Ba0.6Sr0.4TiO3 films

B. H. Park, E. J. Peterson, Q. X. Jia, J. Lee, X. Zeng, W. Si, and X. X. Xi

Appl. Phys. Lett. 78, 533 (2001); http://dx.doi.org/10.1063/1.1340863 (3 pages) | Cited 96 times

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We have epitaxially grown Ba0.6Sr0.4TiO3 (BST-0.4) thin films on MgO(001) substrates. By inserting a very thin Ba1−xSrxTiO3 (x = 0.1–0.7) interlayer between the MgO substrate and the main layer of BST-0.4, we are able to manipulate the degree of the stress in BST-0.4 films. We have controlled the stress states, i.e., the lattice distortion ratio (D = in-plane lattice constant/out-of-plane lattice constant) of the BST-0.4 films by varying the chemical composition of the interlayers. We have found that small variations of D value can result in significantly large changes of dielectric properties. A BST-0.4 film under small tensile stress, which has a D value of 1.0023, shows the largest dielectric permittivity and tunability. © 2001 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
81.15.Fg Pulsed laser ablation deposition
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Construction of highly conductive nanowires on a DNA template

Jan Richter, Michael Mertig, Wolfgang Pompe, Ingolf Mönch, and Hans K. Schackert

Appl. Phys. Lett. 78, 536 (2001); http://dx.doi.org/10.1063/1.1338967 (3 pages) | Cited 125 times

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We present measurements of the electrical conductivity of metallic nanowires which have been fabricated by chemical deposition of a thin continuous palladium film onto single DNA molecules to install electrical functionality. The DNA molecules have been positioned between macroscopic Au electrodes and are metallized afterwards. Low-resistance electrical interfacing was obtained by pinning the nanowires at the electrodes with electron-beam-induced carbon lines. The investigated nanowires exhibit ohmic transport behavior at room temperature. Their specific conductivity is only one order of magnitude below that of bulk palladium, confirming that DNA is an ideal template for the production of electric wires, which can be utilized for the bottom-up construction of miniaturized electrical circuits. © 2001 American Institute of Physics.
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81.07.Lk Nanocontacts
85.65.+h Molecular electronic devices
81.16.Fg Supramolecular and biochemical assembly
73.63.Rt Nanoscale contacts
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
73.40.Cg Contact resistance, contact potential
87.14.G- Nucleic acids
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