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1 Oct 2007

Volume 91, Issue 14, Articles (14xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 143101 (2007); http://dx.doi.org/10.1063/1.2789812 (3 pages)

Hyun S. Kim, Hua Qin, and Robert H. Blick
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Direct mechanical mixing in a nanoelectromechanical diode

Hyun S. Kim, Hua Qin, and Robert H. Blick

Appl. Phys. Lett. 91, 143101 (2007); http://dx.doi.org/10.1063/1.2789812 (3 pages) | Cited 5 times

Online Publication Date: 1 October 2007

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We observe direct mechanical mixing in nanoelectromechanical transistors fabricated in semiconductor materials operating in the radio frequency band of 10–1000 MHz. The device is made of a mechanically flexible pillar with a length of 240 nm and a diameter of 50 nm placed between two electrodes in an impedance matched coplanar wave guide. We find a nonlinear I-V characteristic, which enables radio frequency mixing of two electromagnetic signals via the nanomechanical transistor. Potential applications for this mixer are ultrasensitive displacement detection or signal processing in communication electronic circuits requiring high-throughput insulation.
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85.35.Gv Single electron devices
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Ferromagnetism of Co-doped TiO2(B) nanotubes

X. W. Wang, X. P. Gao, G. R. Li, L. Gao, T. Y. Yan, and H. Y. Zhu

Appl. Phys. Lett. 91, 143102 (2007); http://dx.doi.org/10.1063/1.2789734 (3 pages) | Cited 13 times

Online Publication Date: 1 October 2007

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The Co-doped titanate nanotubes, synthesized via a hydrothermal reaction, are calcined at 300, 400, and 500 °C for 2 h in an argon atmosphere to yield Co-doped TiO2(B) nanotubes and anatase nanotubes with a dark gray color. It is shown that all calcined titania nanotubes have a stronger absorption in visible region, attributed to the formation of oxygen vacancies. The saturation magnetization of all Co-doped titania nanotubes is stronger than that of as-prepared Co-doped titanate nanotubes. In particular, Co-doped TiO2(B) nanotubes calcined at 300 °C exhibit the strongest ferromagnetism due to the existence of oxygen vacancies, as confirmed further by electron paramagnetic resonance spectra.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.16.-c Methods of micro- and nanofabrication and processing
76.30.Mi Color centers and other defects
61.72.J- Point defects and defect clusters

Temperature-dependent photoemission spectroscopy study of RExC60 (RE = Yb and Sm) films

Shaolong He, Masashi Nakatake, Masashi Arita, Xiaoyu Cui, Shan Qiao, Hirofumi Namatame, Masaki Taniguchi, Haiyang Li, and Hongnian Li

Appl. Phys. Lett. 91, 143103 (2007); http://dx.doi.org/10.1063/1.2790377 (3 pages) | Cited 2 times

Online Publication Date: 1 October 2007

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Temperature-dependent electronic structures of RExC60 (where RE denotes Yb and Sm) films have been studied by high-resolution photoemission spectroscopy (PES). Our results indicate that Yb5C60 is the only metallic phase among all the phases in Yb doped C60 films. For the Sm fullerides, PES results show that there is no Sm valence transition during the negative thermal expansion in Sm2.75C60 below 32 K. The Sm valence state in Sm2.75C60 films is nearly +2 at room temperature and remains stable in the films down to 16 K. In addition, the negative thermal expansion effect does not result any distinct change in valence-band electronic structures of Sm2.75C60.
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79.60.Dp Adsorbed layers and thin films
71.20.Tx Fullerenes and related materials; intercalation compounds
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
74.78.-w Superconducting films and low-dimensional structures

Hexagonal Cu2SnS3 with metallic character: Another category of conducting sulfides

Changzheng Wu, Zhenpeng Hu, Chengle Wang, Hua Sheng, Jinlong Yang, and Yi Xie

Appl. Phys. Lett. 91, 143104 (2007); http://dx.doi.org/10.1063/1.2790491 (3 pages) | Cited 11 times

Online Publication Date: 1 October 2007

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A hexagonal Cu2SnS3 with uniform and well-dispersed nanoparticle morphology has been synthesized, representing an example of hexagonal system in the Cu–Sn–E (S, Se) ternary chalcogenides. Both theoretical calculation and experimental results give the unique metallic character of Cu2SnS3, which is significantly different from the traditional opinion that I-IV-VI ternary chalcogenides were regarded previously as small or middle band-gap semiconductors. Also, M(I)2SnS3 (M = Ag, Au, Rb, and Cs) serial compounds are another potential family of conducting sulfides. The conducting Cu2SnS3 product with the interlayer space and tunnels in the crystal structures could be fascinatingly introduced to the lithium battery application.
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61.66.Fn Inorganic compounds
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
82.47.Aa Lithium-ion batteries
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys

Patterning-controlled morphology of spatially and dimensionally constrained oxide nanostructures

Zixiao Pan, Shuyou Li, Zhaoyu Wang, Min-Feng Yu, and Vinayak P. Dravid

Appl. Phys. Lett. 91, 143105 (2007); http://dx.doi.org/10.1063/1.2790496 (3 pages) | Cited 5 times

Online Publication Date: 1 October 2007

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This letter reports a facile approach for morphologic control of complex oxide nanostructures patterned by “soft” electron beam lithography (soft-eBL). The authors demonstrate fabrication of epitaxial nanofrustum and nanopyramidal morphologies of ferroelectric BaTiO3 and magnetic CoFe2O4 lines, with controlled zig-zag or smooth edges. The dimensional and shape control is achieved by simply tuning the patterning parameters such as resist thickness and patterning directions with respect to underlying substrate orientation. The crystal orientation, element distribution, and piezoelectric behavior of BaTiO3 nanofrustums are evaluated with analytical transmission electron microscopy and piezoresponse force microscopy. It is argued that soft-eBL allows for exquisite control over morphology, shape evolution, and orientation of zero- and one-dimensional nanostructures akin to what has been possible in the past with semiconductor heterostructures by thin film approaches.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.07.Bc Nanocrystalline materials
81.16.Nd Micro- and nanolithography
61.46.Hk Nanocrystals
75.50.Gg Ferrimagnetics
77.80.-e Ferroelectricity and antiferroelectricity

Rapid directed self assembly of lamellar microdomains from a block copolymer containing hybrid

Joy Y. Cheng, Jed Pitera, Oun-Ho Park, Myron Flickner, Ricardo Ruiz, Charles T. Black, and Ho-Cheol Kim

Appl. Phys. Lett. 91, 143106 (2007); http://dx.doi.org/10.1063/1.2791003 (3 pages) | Cited 10 times

Online Publication Date: 1 October 2007

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The directed self-assembly of a lamellar-forming hybrid block copolymer system comprising of a poly(styrene-b-ethylene oxide) and organosilicates (OSs) has been investigated. The addition of OS to the block copolymer is found to provide additional control over the persistence length of lamellae as well as the behavior of directed self assembly. Two OSs with different molecular weights and reactivities have been compared in this experiment. Both OSs yield the same local structure of lamellar domains but different degrees of mid- and long-range order. Longer correlation length and better alignment of lamellar domains were observed with the lower molecular weight, more reactive OS, which suggest a potential guidance for controlling over microdomains in block copolymer-containing hybrid systems.
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61.41.+e Polymers, elastomers, and plastics
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.16.Dn Self-assembly

A very low temperature single crystal germanium growth process on insulating substrate using Ni-induced lateral crystallization for three-dimensional integrated circuits

Jin-Hong Park, Pawan Kapur, Krishna C. Saraswat, and Hailin Peng

Appl. Phys. Lett. 91, 143107 (2007); http://dx.doi.org/10.1063/1.2793183 (3 pages) | Cited 16 times

Online Publication Date: 1 October 2007

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Metal (Ni)-induced lateral crystallization (MILC) of amorphous (α)-germanium (Ge) films on silicon dioxide (SiO2) is investigated on α-Ge planar films, annealing at 350–380 °C in a N2 ambient. MILC is not observed after annealing for 1 h at 350 °C, and self-nucleation with its small, deleterious microcrystals plagues the process at 380 °C. 360 °C is determined to be an optimum annealing temperature. These conditions are subsequently applied to a patterned nanowire to obtain a single-crystal Ge wire on SiO2. The method is promising for integrating high quality Ge transistors at low temperatures as required by three-dimensional integrated circuits.
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81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
64.70.D- Solid-liquid transitions
61.72.Cc Kinetics of defect formation and annealing

Layer-by-layer assembly of capped CdSe nanoparticles: Electrical bistability and memory phenomenon

Satyajit Sahu, Swarup K. Majee, and Amlan J. Pal

Appl. Phys. Lett. 91, 143108 (2007); http://dx.doi.org/10.1063/1.2793617 (3 pages) | Cited 13 times

Online Publication Date: 1 October 2007

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The authors demonstrate thin-film formation of capped-CdSe nanoparticles via layer-by-layer electrostatic assembly. The assembly of two types of nanoparticles in sequence—with anionic and cationic capping agents, respectively—results in thin films of CdSe nanoparticles. Devices based on such thin films demonstrate electrical bistability. The bistability, which is reversible in nature, is due to charge confinement in the nanoparticles and has an associated memory phenomenon. The devices based on the CdSe nanoparticles exhibit high on/off ratio and demonstrate read-only and random-access memory applications.
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81.07.Bc Nanocrystalline materials
81.05.Dz II-VI semiconductors
81.16.Dn Self-assembly
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.A- Nucleation and growth
73.61.Ga II-VI semiconductors

Design and fabrication of segmented, slotted waveguides for electro-optic modulation

Guangxi Wang, Tom Baehr-Jones, Michael Hochberg, and Axel Scherer

Appl. Phys. Lett. 91, 143109 (2007); http://dx.doi.org/10.1063/1.2793618 (3 pages) | Cited 20 times

Online Publication Date: 1 October 2007

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Recently, slotted waveguides have been used in conjunction with second order nonlinear optical polymers to provide a platform for electro-optic modulation at telecommunication frequencies. A challenge with these devices is the need to provide high-frequency electrical driving signals to the slots. The silicon resistivity must be high to reduce optical loss, and as a result electrical performance can be severely limited. We have designed and fabricated a class of waveguide that achieves quasicontinuous electrical contact with subwavelength segmentations and has low optical losses of 4 dB/cm, allowing both millimeter-wave and optical fields to be concentrated in the same area.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Gn Optical waveguides and couplers

Large-area, ordered hexagonal arrays of nanoscale holes or dots from block copolymer templates

Josee Vedrine, Young-Rae Hong, Andrew P. Marencic, Richard A. Register, Douglas H. Adamson, and Paul M. Chaikin

Appl. Phys. Lett. 91, 143110 (2007); http://dx.doi.org/10.1063/1.2794010 (3 pages) | Cited 9 times

Online Publication Date: 1 October 2007

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Hexagonal arrays of nanoscale holes or metal dots (25 nm in diameter and 39 nm in period), with orientational order extending over the entire square-centimeter array area, were fabricated on unpatterned silicon wafer substrates using a shear-aligned sphere-forming diblock copolymer template. Since two or more layers of spherical nanodomains are required to achieve alignment in the block copolymer film, but pattern transfer requires a single layer, a multistep etching process was developed, whereby the top layer of a shear-aligned bilayer was evenly removed, leaving the ordered bottom layer as the fabrication template for hole and dot arrays free from grain boundaries.
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81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
81.07.Ta Quantum dots
81.05.Bx Metals, semimetals, and alloys
81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning

Contact potential measurement using a heated atomic force microscope tip

Jessica L. Remmert, Yan Wu, Jungchul Lee, Mark A. Shannon, and William P. King

Appl. Phys. Lett. 91, 143111 (2007); http://dx.doi.org/10.1063/1.2789927 (3 pages) | Cited 8 times

Online Publication Date: 2 October 2007

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This letter reports contact potential measurement between the tip of a heated atomic force microscope cantilever and a biased gold film. Force-distance experiments were performed with tip temperature, tip potential, and substrate potential independently controlled. Experiments were conducted for probe temperatures of 23 to 200 °C and tip potentials of −1 V to 1 V. The measured contact potential was a function of temperature, due to the thermoelectric properties of the tip and substrate. The Seebeck coefficient for the combined system was close to −4.30 mV/K, consistent with the tip and substrate materials. The technique is scalable to arrays suitable for large area imaging.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
73.50.Lw Thermoelectric effects
72.15.Jf Thermoelectric and thermomagnetic effects
72.20.Pa Thermoelectric and thermomagnetic effects
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Direct imaging of quantum wires nucleated at diatomic steps

S. I. Molina, M. Varela, D. L. Sales, T. Ben, J. Pizarro, P. L. Galindo, D. Fuster, Y. González, L. González, and S. J. Pennycook

Appl. Phys. Lett. 91, 143112 (2007); http://dx.doi.org/10.1063/1.2790483 (3 pages) | Cited 4 times

Online Publication Date: 2 October 2007

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Atomic steps at growth surfaces are important heterogeneous sources for nucleation of epitaxial nano-objects. In the presence of misfit strain, we show that the nucleation process takes place preferentially at the upper terrace of the step as a result of the local stress relaxation. Evidence for strain-induced nucleation comes from the direct observation by postgrowth, atomic resolution, Z-contrast imaging of an InAs-rich region in a nanowire located on the upper terrace surface of an interfacial diatomic step.
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81.07.Vb Quantum wires
81.05.Ea III-V semiconductors
81.16.Dn Self-assembly
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.La Quantum wires (patterned in quantum wells)
81.40.Jj Elasticity and anelasticity, stress-strain relations

Frequency response of an atomic force microscope in liquids and air: Magnetic versus acoustic excitation

Elena T. Herruzo and Ricardo Garcia

Appl. Phys. Lett. 91, 143113 (2007); http://dx.doi.org/10.1063/1.2794426 (3 pages) | Cited 19 times

Online Publication Date: 2 October 2007

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We discuss the dynamics of an amplitude modulation atomic force microscope in different environments such as water and air. Experiments, analytical expressions, and numerical simulations show that the resonance curves depend on the excitation method used to drive the cantilever, either mechanical or magnetic. This dependence is magnified for small force constants and quality factors, i.e., below 1 N/m and 10, respectively. We show that the equation for the observable, the cantilever deflection, depends on the excitation method. Under mechanical excitation, the deflection involves the base and tip displacements, while in magnetic excitation, the cantilever deflection and tip displacement coincide.
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07.79.Lh Atomic force microscopes
07.10.Cm Micromechanical devices and systems

In situ integration of freestanding zinc oxide nanorods using copper silicide nanobeams

Nitin Kumar, Omkar Parajuli, and Jong-in Hahm

Appl. Phys. Lett. 91, 143114 (2007); http://dx.doi.org/10.1063/1.2794403 (3 pages) | Cited 3 times

Online Publication Date: 3 October 2007

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In this letter, we describe an in situ integration method to produce freestanding zinc oxide nanorods (ZnO NRs) on copper silicide nanobeams (Cu3Si NBs). The integration of ZnO NRs with Cu3Si NBs is straightforwardly achieved immediately after ZnO NR synthesis by exploiting self-assembled Cu3Si NBs as catalysts. The resulting ZnO NRs on Cu3Si NBs exhibit atomic defect-free structures with superb optical quality which, in turn, can be beneficial when applied in micro- and nanoelectromechanical systems.
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81.05.Dz II-VI semiconductors
81.07.Bc Nanocrystalline materials
81.16.Dn Self-assembly

Defects in interfacial layers and their role in the growth of ZnO nanorods by metallorganic chemical vapor deposition

Dong Jun Park, Jeong Yong Lee, Dong Chan Kim, Sanjay Kumar Mohanta, and Hyung Koun Cho

Appl. Phys. Lett. 91, 143115 (2007); http://dx.doi.org/10.1063/1.2794418 (3 pages) | Cited 10 times

Online Publication Date: 3 October 2007

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We report the evolution of ZnO nanorods by metalorganic chemical vapor deposition on sapphire substrates and an investigation of their microstructure. Well-aligned ZnO nanorods with a high aspect ratio were grown on an interfacial layer with several types of defects at a lower reactor pressure. Planar defects such as stacking mismatch boundaries and inversion domain boundaries were formed in the interfacial layer during the coalescence of the islands, and finally constituted the side facets of the nanorods. Based on the microstructural changes and origin of the defects in the interfacial layers, we propose a model to explain the growth evolution of ZnO nanorods on sapphire substrates.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Be Chemical synthesis methods
61.72.Nn Stacking faults and other planar or extended defects
61.72.Mm Grain and twin boundaries
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Boron-doped carbon nanotube coating for transparent, conducting, flexible photonic devices

Quinton L. Williams, Xi Liu, Wilbur Walters, Jr., Jian-Ge Zhou, Tylvia Y. Edwards, Franchesca L. Smith, Gregory E. Williams, and Brenitra L. Mosley

Appl. Phys. Lett. 91, 143116 (2007); http://dx.doi.org/10.1063/1.2795343 (3 pages) | Cited 5 times

Online Publication Date: 3 October 2007

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Conducting transparent polymer materials were made by applying boron-doped single-walled carbon nanotubes to the surfaces of glass and flexible polyethylene terephthalate film substrates. Optical transmission and sheet resistance measurements showed that the boron-doped coated samples had sheet resistances of ∼ 7 kΩ/◻ and flat optical transmission of ∼ 89% for visible light. Temperature and humidity tests showed that the materials remained conductive after nearly 150 h of testing. The materials are robust and even maintain their conducting properties after being folded. Fabrication of a simple light emitting device demonstrates usage of the material as a flexible transparent electrode.
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85.60.Jb Light-emitting devices

Nanoimprinting of conductive tracks using metal nanopowders

Seok-min Kim, Jinsu Kim, Jiseok Lim, Minseok Choi, Shinill Kang, Sukwon Lee, and Hyuk Kim

Appl. Phys. Lett. 91, 143117 (2007); http://dx.doi.org/10.1063/1.2795789 (3 pages) | Cited 1 time

Online Publication Date: 3 October 2007

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A method for metal nanopowder imprinting is proposed as a patterning process for conductive tracks, which is inexpensive and scalable down to submicrometers. To examine the feasibility of the proposed method, conductive tracks with widths of submicrometers to a few tens of micrometers were formed using a thermal nanoimprinting system, and the effects of processing conditions on the degree of replication and the degree of sintering and the electric conductivity of imprinted conductive tracks were analyzed.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.07.Wx Nanopowders
81.16.Rf Micro- and nanoscale pattern formation
81.16.Nd Micro- and nanolithography
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Hysteretic transfer characteristics of double-walled and single-walled carbon nanotube field-effect transistors

Shaoning Yuan, Qing Zhang, Daisuke Shimamoto, Hiroyuki Muramatsu, Takuya Hayashi, Yoong Ahm Kim, and Morinobu Endo

Appl. Phys. Lett. 91, 143118 (2007); http://dx.doi.org/10.1063/1.2789789 (3 pages) | Cited 5 times

Online Publication Date: 4 October 2007

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In both double-walled carbon nanotube field-effect transistors (DWCNT-FETs) and single-walled carbon nanotube field-effect transistors (SWCNT-FETs), “clockwise” hysteretic transfer characteristics are observed. These characteristics can be attributed to mobile ions or charged clusters in surfactant layers around the tube channels. Compared with SWCNT-FETs, more significant surfactant influences on the transfer characteristics are observed in DWCNT-FETs due to superior surfactant adsorption properties of double-walled carbon nanotubes. Our findings suggest that not only water molecules but also the surfactants play critical roles in dominating the hystereses, especially when the carbon nanotubes are double walled.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices

Diffraction-limited phonon thermal conductance of nanoconstrictions

Ravi Prasher, Tao Tong, and Arun Majumdar

Appl. Phys. Lett. 91, 143119 (2007); http://dx.doi.org/10.1063/1.2794428 (3 pages) | Cited 7 times

Online Publication Date: 4 October 2007

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Thermal transport across nanosized constrictions is calculated considering wave effects. It is shown that Rayleigh-type phonon diffraction reduces thermal transport across nanosized constrictions at low temperatures. We show that for aT/vDebye<0.01×10−9 K s, where a is the radius of the constriction, T the temperature, and vDebye the Debye velocity of the solid material, diffraction effects are important.
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63.20.-e Phonons in crystal lattices
72.20.-i Conductivity phenomena in semiconductors and insulators

Evidence for low density of nonradiative defects in ZnO nanowires grown by metal organic vapor-phase epitaxy

I. C. Robin, B. Gauron, P. Ferret, C. Tavares, G. Feuillet, Le Si Dang, B. Gayral, and J. M. Gérard

Appl. Phys. Lett. 91, 143120 (2007); http://dx.doi.org/10.1063/1.2794790 (3 pages) | Cited 12 times

Online Publication Date: 4 October 2007

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Low temperature cathodoluminescence and temperature dependent time resolved photoluminescence are used to investigate the emission properties of ZnO nanowires grown by metal organic vapor phase epitaxy. Low temperature cathodoluminescence images show that the emission process is more efficient in ZnO nanowires than in the underlying two dimensional layer. Temperature dependent photoluminescence spectra and decay time measurements give a detailed insight on the role of the donor bound exciton, the free exciton, and the nonradiative channels in the emission process. In particular, it is shown that up to room temperature, the escape toward nonradiative channels is limited because of the very low defect density in the ZnO nanowires.
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78.67.Lt Quantum wires
78.60.Hk Cathodoluminescence, ionoluminescence
78.55.Et II-VI semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
71.35.-y Excitons and related phenomena

Metal heterowaveguide superlattices for a plasmonic analog to electronic Bloch oscillations

Weihua Lin and Guo Ping Wang

Appl. Phys. Lett. 91, 143121 (2007); http://dx.doi.org/10.1063/1.2795344 (3 pages) | Cited 25 times

Online Publication Date: 4 October 2007

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A metal heterowaveguide superlattice constructed by alternately stacking two metal gap waveguides with gradually changed geometric thicknesses for observing time-resolved plasmon Bloch oscillations (PBOs) is presented. Analytical result from the transfer matrix method reveals the appearance of tilted plasmonic minibands and minigaps, and plasmonic Wannier-Stark ladder in frequency domain, indicating the existence of time-resolved PBO effects in such superlattices. Finite-difference time-domain simulations on the dynamic evolution of plasmon propagation in the superlattices demonstrate the analytical prediction.
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73.22.Lp Collective excitations
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.79.Gn Optical waveguides and couplers
68.65.Cd Superlattices

Tunable optical negative-index metamaterials employing anisotropic liquid crystals

Xiande Wang, Do-Hoon Kwon, Douglas H. Werner, Iam-Choon Khoo, Alexander V. Kildishev, and Vladimir M. Shalaev

Appl. Phys. Lett. 91, 143122 (2007); http://dx.doi.org/10.1063/1.2795345 (3 pages) | Cited 29 times

Online Publication Date: 4 October 2007

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A full-wave analysis technique based on the finite element-boundary integral method is developed and used to rigorously treat the scattering from periodically structured metamaterials incorporating anisotropic liquid crystals (LCs) and dispersive materials. Reconfiguration of the negative-index metamaterials is achieved by controlling the magnetic resonance via tuning permittivity of the embedded anisotropic LCs. Numerical results show that the refractive index of the metamaterials can be reconfigured by tuning the director orientation of anisotropic LCs or by using temperature-dependent LCs. The design configurations and their characteristics in the near- and the mid-infrared ranges are presented.
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42.70.Df Liquid crystals
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Controlled, perfect ordering in ultrathin anodic aluminum oxide templates on silicon

Adam P. Robinson, Gavin Burnell, Mingzhe Hu, and Judith L. MacManus-Driscoll

Appl. Phys. Lett. 91, 143123 (2007); http://dx.doi.org/10.1063/1.2794031 (3 pages) | Cited 13 times

Online Publication Date: 5 October 2007

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Ultrathin, perfectly ordered anodic aluminum oxide templates have been produced on supporting substrates by focused ion beam prepatterning. This fast, flexible approach produces pore arrays with both hexagonal and square geometries and allows control over the pore pitch and diameter. The orientation of ordering can be controlled with nanometer precision. Pattern transfer into Si produces pore densities of up to 1011 in.−2.
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68.55.-a Thin film structure and morphology
61.43.Gt Powders, porous materials
81.16.Rf Micro- and nanoscale pattern formation

Localized reversible nanoscale phase separation in Pr0.63Ca0.37MnO3 single crystal using a scanning tunneling microscope tip

Sohini Kar and A. K. Raychaudhuri

Appl. Phys. Lett. 91, 143124 (2007); http://dx.doi.org/10.1063/1.2794795 (3 pages) | Cited 4 times

Online Publication Date: 5 October 2007

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We report the destabilization of the charge ordered insulating (COI) state in a localized region of Pr0.63Ca0.37MnO3 single crystal by current injection using a scanning tunneling microscope tip. This leads to controlled phase separation and formation of localized metallic nanoislands in the COI matrix which have been detected by local tunneling conductance mapping. The metallic regions thus created persist even after reducing the injected current to lower values. The original conductance state can be restored by injecting a current of similar magnitude but of opposite polarity. We thus achieve reversible nanoscale phase separation that gives rise to the possibility to “write, read, and erase” nanosized conducting regions in an insulating matrix with high spatial resolution.
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64.75.-g Phase equilibria
71.45.-d Collective effects
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