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6 Oct 2008

Volume 93, Issue 14, Articles (14xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 141901 (2008); http://dx.doi.org/10.1063/1.2990662 (3 pages)

J. H. Han, K. B. Kim, S. Yi, J. M. Park, S. W. Sohn, T. E. Kim, D. H. Kim, J. Das, and J. Eckert
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Interface as the origin of ferromagnetism in cobalt doped ZnO film grown on silicon substrate

Z. G. Yin, N. F. Chen, Y. Li, X. W. Zhang, Y. M. Bai, C. L. Chai, Y. N. Xie, and J. Zhang

Appl. Phys. Lett. 93, 142109 (2008); http://dx.doi.org/10.1063/1.2989128 (3 pages) | Cited 3 times

Online Publication Date: 10 October 2008

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We have investigated the magnetic properties of Co-doped zinc oxide (ZnO) film deposited on silicon substrate by magnetron sputtering. Co ions have a valence of 2+ and substitute for Zn sites in the lattice. By using a chemical etching method, an extrinsic ferromagnetism was demonstrated. The observed ferromagnetism is neither associated with magnetic precipitates nor with contamination, but originates from the silicon/silicon oxide interface. This interface ferromagnetism is characterized by being temperature independent and by having a parallel magnetic anisotropy.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.ag Semiconductors
75.50.Pp Magnetic semiconductors
75.30.Gw Magnetic anisotropy
81.15.Cd Deposition by sputtering
75.50.Dd Nonmetallic ferromagnetic materials

Two insulating phases in compressed Pr1−xCaxMnO3 thin films

M. Filippi, W. Prellier, P. Auban-Senzier, and C. R. Pasquier

Appl. Phys. Lett. 93, 142110 (2008); http://dx.doi.org/10.1063/1.2993347 (3 pages) | Cited 7 times

Online Publication Date: 10 October 2008

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The temperature-dependent resistivity of two Pr1−xCaxMnO3 (x = 0.5 and 0.6) thin films grown on LaAlO3 has been studied as a function of hydrostatic pressure (up to 2.5 GPa) and magnetic field (up to 9 T). Both samples show a monotonic decrease in the resistivity with an increase in pressure, corresponding to a change of −35% at 2.5 GPa. No pressure induced metal-to-insulator transition was observed in the temperature-dependent resistivity. The nontrivial interaction between high pressure and magnetic field reveals that the effect of pressure cannot be simply rescaled to that of a specific field, as has been reported for the corresponding bulk material. We propose an interpretation of the data based on phase separation, where two different insulating phases coexist: the charge ordered phase, which is sensitive to both magnetic field and pressure, and a second insulating phase that can be tuned by magnetic field. Such a result demonstrates that phase separation can be manipulated in thin films by independent application of magnetic field and/or external pressure.
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73.61.Ng Insulators
72.60.+g Mixed conductivity and conductivity transitions

Transparent Al–Zn–Sn–O thin film transistors prepared at low temperature

Doo-Hee Cho, Shinhyuk Yang, Chunwon Byun, Jaeheon Shin, Min Ki Ryu, Sang-Hee Ko Park, Chi-Sun Hwang, Sung Mook Chung, Woo-Seok Cheong, Sung Min Yoon, and Hye-Yong Chu

Appl. Phys. Lett. 93, 142111 (2008); http://dx.doi.org/10.1063/1.2998612 (3 pages) | Cited 49 times

Online Publication Date: 10 October 2008

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We have fabricated transparent bottom gate thin film transistors (TFTs) using Al-doped zinc tin oxide (AZTO) as active layers. The AZTO active layer was deposited by rf magnetron sputtering at room temperature. The AZTO TFT showed good TFT performance without postannealing. The field effect mobility and the subthreshold swing were improved by postannealing below 180 °C. The AZTO TFT exhibited a field effect mobility (μFET) of 10.1 cm2/V s, a turn-on voltage (Von) of 0.4 V, a subthreshold swing (S/S) of 0.6 V/decade, and an on/off ratio (Ion/Ioff) of 109.
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85.30.Tv Field effect devices
85.40.Sz Deposition technology
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Frequency modulation effect on microwave assisted magnetization switching

S. Okamoto, N. Kikuchi, and O. Kitakami

Appl. Phys. Lett. 93, 142501 (2008); http://dx.doi.org/10.1063/1.2996573 (3 pages) | Cited 10 times

Online Publication Date: 6 October 2008

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Frequency modulation (FM) effect on the microwave assisted switching (MAS) of magnetization has been studied by calculating the Landau–Lifshitz–Gilbert equation. Application of FM microwave can significantly reduce the switching field compared with constant frequency wave, mainly due to more effective microwave energy absorption by the spin system. The FM effect on the MAS is remarkable especially for smaller Gilbert damping of α ⩽ 0.02. For sufficient switching probability, the FM-MAS requires somewhat longer time of a few nanoseconds for the dc magnetic field parallel to the easy axis. The tilt dc field can effectively reduce the switching time.
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75.60.Jk Magnetization reversal mechanisms
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

Spatial distribution of manganese and room temperature ferromagnetism in manganese-doped ZnO nanorods

H. L. Yan, J. B. Wang, X. L. Zhong, and Y. C. Zhou

Appl. Phys. Lett. 93, 142502 (2008); http://dx.doi.org/10.1063/1.2993354 (3 pages) | Cited 11 times

Online Publication Date: 6 October 2008

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Monochromatic cathodoluminescence image of Mn-doped ZnO nanorods shows that Mn elements are mainly distributed on the surface of nanorods. The intensity of ultraviolet luminescence decreases with the increment in Mn-doped concentration. Mn-doped ZnO nanorods exhibit a room temperature ferromagnetic characteristic with a saturation magnetization (MS) of 0.39 μB/Mn and a coercive field of 50 Oe.
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78.60.Hk Cathodoluminescence, ionoluminescence
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Subterahertz excitations and magnetoelectric effects in hexaferrite-piezoelectric bilayers

Alexey B. Ustinov and G. Srinivasan

Appl. Phys. Lett. 93, 142503 (2008); http://dx.doi.org/10.1063/1.2996585 (3 pages) | Cited 5 times

Online Publication Date: 7 October 2008

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A frequency-agile hexaferrite-piezoelectric composite for potential device applications at subterahertz frequencies is studied. The bilayer is composed of aluminum substituted barium hexagonal ferrite (BaAl2Fe10O19) and lead zirconate titanate (PZT). A dc electric field applied to PZT results in mechanical deformation of the ferrite, leading to a frequency shift in ferromagnetic resonance. The bilayer demonstrates magnetoelectric interaction coefficient of about 0.37 Oe cm/kV.
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77.65.-j Piezoelectricity and electromechanical effects
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
75.50.Gg Ferrimagnetics

Phase field modeling of magnetization processes in growth twinned Terfenol-D crystals

Yongxin Y. Huang and Yongmei M. Jin

Appl. Phys. Lett. 93, 142504 (2008); http://dx.doi.org/10.1063/1.2996586 (3 pages) | Cited 8 times

Online Publication Date: 8 October 2008

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Phase field micromagnetic microelastic modeling is used to simulate magnetization processes in growth twinned Terfenol-D crystals under external magnetic field applied along the [11math] growth direction. The simulations reveal complex domain microstructure evolution involving both magnetization rotation and domain wall motion. It is found that domains strongly interact across the (111) growth twin boundaries. The competitions among magnetostatic, elastic, and magnetocrystalline anisotropy energies are analyzed, which explains the underlying domain mechanisms responsible for the experimentally observed magnetostriction jump effect in growth twinned Terfenol-D crystals.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
61.72.Mm Grain and twin boundaries
75.60.Ch Domain walls and domain structure
75.80.+q Magnetomechanical effects, magnetostriction

Ferromagnetic resonance signature of metallic Co clusters in ferromagnetic ZnCoO thin films

H. J. von Bardeleben, N. Jedrecy, and J. L. Cantin

Appl. Phys. Lett. 93, 142505 (2008); http://dx.doi.org/10.1063/1.2998309 (3 pages) | Cited 5 times

Online Publication Date: 8 October 2008

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Highly Co-doped Zn0.7Co0.3O thin films that can be reproducibly grown ferromagnetic by pulsed laser deposition have been investigated by optical absorption and ferromagnetic resonance spectroscopy (FMR). The saturation magnetization depends strongly on the O2 content during the growth, the highest value being obtained for the lowest oxygen pressure conditions. Whereas the optical absorption spectra confirm the incorporation of Co as CoZn2+ in ZnO, the FMR spectra prove the additional presence of randomly oriented metallic Co nanoparticles. The angular variation in the FMR spectra allows us to determine in the most ferromagnetic film the effective magnetization, 4πM ∼ 800 G at 300 K and the g factor, g = 2.18, which is that of metallic Co. The fraction of the two species CoZn2+ and Co metal is estimated to be ∼ 3:1
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
68.55.ag Semiconductors
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance

Fishtail effect and the vortex phase diagram of single crystal Ba0.6K0.4Fe2As2

Huan Yang, Huiqian Luo, Zhaosheng Wang, and Hai-Hu Wen

Appl. Phys. Lett. 93, 142506 (2008); http://dx.doi.org/10.1063/1.2996576 (3 pages) | Cited 39 times

Online Publication Date: 9 October 2008

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By measuring the magnetization hysteresis loops of superconducting Ba0.6K0.4Fe2As2 single crystals, we obtained the high upper critical field and large current carrying ability, which point to optimistic applications. The fishtail (or second peak) effect is also found in the material, and the position of the vortex pinning force shows a maximum at 1/3 of the reduced field, being consistent with the picture of vortex pinning by small size normal cores in the sample. Together with the resistive measurements, for the first time the vortex phase diagram is obtained for superconductor Ba0.6K0.4Fe2As2.
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74.25.Op Mixed states, critical fields, and surface sheaths
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Dw Superconductivity phase diagrams
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.70.Dd Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.)

Room temperature anomalous Hall effect in Co doped ZnO thin films in the semiconductor regime

H. S. Hsu, C. P. Lin, H. Chou, and J. C. A. Huang

Appl. Phys. Lett. 93, 142507 (2008); http://dx.doi.org/10.1063/1.3000015 (3 pages) | Cited 8 times

Online Publication Date: 10 October 2008

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Observation of the room temperature (RT) anomalous Hall effect (AHE) and ferromagnetism in semiconducting like (carrier concentration ∼ 1019 cm−3) Co-doped ZnO samples is reported. These small AHE signals match quantitatively with the magnetic hysteresis and can be correspondent to the intrinsic diluted magnetic oxide (DMO) effect with spin polarized carriers. The contribution to the DMO effect depends on the types of carriers and how they incorporated into the electric conduction, magnetic coupling, and the coupling between them. These findings can provide useful information in the study of the origin of RT ferromagnetism in ZnO-based DMO and for further application in spintronics.
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68.55.ag Semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.25.-b Spin polarized transport

Current controlled random-access memory based on magnetic vortex handedness

Stellan Bohlens, Benjamin Krüger, André Drews, Markus Bolte, Guido Meier, and Daniela Pfannkuche

Appl. Phys. Lett. 93, 142508 (2008); http://dx.doi.org/10.1063/1.2998584 (3 pages) | Cited 37 times

Online Publication Date: 10 October 2008

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The theoretical foundation for a nonvolatile memory device based on magnetic vortices is presented. We propose a realization of a vortex random-access memory (VRAM) containing vortex cells that are controlled by alternating currents only. The proposed scheme allows to transfer the vortex into an unambiguous binary state regardless of its initial state within a subnanosecond time scale. The vortex handedness defined as the product of chirality and polarization as a bit representation allows direct mechanisms for reading and writing the bit information. The VRAM is stable at room temperature.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
84.30.Sk Pulse and digital circuits

C-axis persistent current and Cooper-pair tunneling through intrinsic Josephson junctions in a ring-shaped YBa2Cu3O7−δ film

A. I. Mansour, M. M. Saber, K. H. Chow, and J. Jung

Appl. Phys. Lett. 93, 142509 (2008); http://dx.doi.org/10.1063/1.2999627 (3 pages) | Cited 2 times

Online Publication Date: 10 October 2008

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We report the direct experimental observation of the temperature dependence of the persistent current Icj due to tunneling Cooper pairs along the c-axis intrinsic Josephson junctions integrated into YBa2Cu3O7−δ ring-shaped thin films. The measured Icj exhibits a linear temperature dependence over a wide range of temperatures well below Tc. Similar behavior was observed in different samples, confirming the reproducibility of the fabrication technique and the reliability of the results.
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74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors

Large magnetic circular dichroism of Co clusters in Co-doped ZnO

Y. Fukuma, H. Asada, J. Yamamoto, F. Odawara, and T. Koyanagi

Appl. Phys. Lett. 93, 142510 (2008); http://dx.doi.org/10.1063/1.2992631 (3 pages) | Cited 4 times

Online Publication Date: 10 October 2008

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Large magnetic circular dichroism (MCD) in Co-doped ZnO films is reported. The Co-( ∼ 20%) doped ZnO films with oxygen deficiencies show ferromagnetic behavior at room temperature. While paramagnetic films exhibit a small MCD signal, broad MCD spectra with large amplitude of ∼ 20 kdeg/cm are observed for the ferromagnetic films. In the ferromagnetic films, Co cluster formation occurs, especially near the interface between the substrate and the film. The amount of the Co clusters is consistent with the spontaneous magnetization and the amplitude of the MCD.
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78.66.Hf II-VI semiconductors
78.20.Ls Magneto-optical effects
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.20.Ck Nonmetals

Epitaxial growth of MgO and Fe/MgO/Fe magnetic tunnel junctions on (100)-Si by molecular beam epitaxy

G. X. Miao, J. Y. Chang, M. J. van Veenhuizen, K. Thiel, M. Seibt, G. Eilers, M. Münzenberg, and J. S. Moodera

Appl. Phys. Lett. 93, 142511 (2008); http://dx.doi.org/10.1063/1.2999633 (3 pages) | Cited 15 times

Online Publication Date: 10 October 2008

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Epitaxial growth of MgO barrier on Si is of technological importance due to the symmetry filtering effect of the MgO barrier in conjunction with bcc-ferromagnets. We study the epitaxial growth of MgO on (100)-Si by molecular beam epitaxy. MgO matches Si with 4:3 cell ratio, which renders Fe to be 45° rotated relative to Si, in sharp contrast to the direct epitaxial growth of Fe on Si. The compressive strains from Si lead to the formation of small angle grain boundaries in MgO below 5 nm, and also affect the transport characteristics of Fe/MgO/Fe magnetic tunnel junctions formed on top.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.60.Bs Mechanical and acoustical properties
61.72.Mm Grain and twin boundaries
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Ferroelectric domain wall pinning at a bicrystal grain boundary in bismuth ferrite

Brian J. Rodriguez, Y. H. Chu, R. Ramesh, and Sergei V. Kalinin

Appl. Phys. Lett. 93, 142901 (2008); http://dx.doi.org/10.1063/1.2993327 (3 pages) | Cited 8 times

Online Publication Date: 6 October 2008

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The ferroelectric polarization switching behavior at the 24° (100) tilt grain boundary (GB) in an epitaxial multiferroic BiFeO3 bicrystal film is studied using piezoresponse force microscopy (PFM). The PFM amplitudes across positively and negatively poled GB regions suggest the presence of a frozen polarization component at the interface. The switching experiments demonstrate that the GB attracts the domain wall and acts as a pinning center. The PFM results are compared with conductive atomic force microscopy and spectroscopy, which suggest domain wall pinning at the GB can be partially attributed to increased conductance at the GB.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Piezoelectric behavior of SrRuO3 buffered lanthanum modified bismuth ferrite thin films grown by chemical method

A. Z. Simões, A. H. M. Gonzalez, E. C. Aguiar, C. S. Riccardi, E. Longo, and J. A. Varela

Appl. Phys. Lett. 93, 142902 (2008); http://dx.doi.org/10.1063/1.2979692 (3 pages) | Cited 3 times

Online Publication Date: 7 October 2008

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Lanthanum modified bismuth ferrite thin film (BLFO) of pure perovskite phase was deposited on SrRuO3-buffered Pt/TiO2/SiO2/Si (100) substrates by soft chemical method. (111)-preferred oriented BLFO film was coherently grown at a temperature of 500 °C. The crystal structure of the film was characterized by using x-ray diffraction. The spontaneous polarization of the film was 25 μC/cm2. The film has a piezoelectric coefficient d33 equal to 85 pm/V and a weak pulse width dependence indicating intrinsic ferroelectricity. Retention measurement showed no decay of polarization while piezoelectric response was greatly improved by the conductor electrode.
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77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects
61.66.Fn Inorganic compounds
75.50.Gg Ferrimagnetics
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization
68.55.at Other materials

Antiferroelectric dielectric relaxation processes and the interlayer interaction in antiferroelectric liquid crystals

Jang-Kun Song, U. Manna, A. Fukuda, and J. K. Vij

Appl. Phys. Lett. 93, 142903 (2008); http://dx.doi.org/10.1063/1.2977871 (3 pages) | Cited 4 times

Online Publication Date: 7 October 2008

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Antiphase relaxation process of antiferroelectric phase is investigated in binary mixtures of antiferroelectric and ferroelectric liquid crystalline compounds. It is found that the frequency of the antiphase mode ranges from 2 to 4 MHz, being one of the fastest collective processes reported so far. This can be exploited in a photonic switch with a submicrosecond response time. However, the frequency of the antiphase mode decreases by the mixing ratio of the ferroelectric compound. The decrease in the frequency is shown to be due to a reduction in the elastic constant in between the adjacent layers.
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77.80.-e Ferroelectricity and antiferroelectricity
61.30.-v Liquid crystals
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.22.Gm Dielectric loss and relaxation
64.70.M- Transitions in liquid crystals

Leakage mechanisms of self-assembled (BiFeO3)0.5:(Sm2O3)0.5 nanocomposite films

H. Yang, H. Wang, G. F. Zou, M. Jain, N. A. Suvorova, D. M. Feldmann, P. C. Dowden, R. F. DePaula, J. L. MacManus-Driscoll, A. J. Taylor, and Q. X. Jia

Appl. Phys. Lett. 93, 142904 (2008); http://dx.doi.org/10.1063/1.3000013 (3 pages) | Cited 11 times

Online Publication Date: 10 October 2008

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Nanocomposite (BiFeO3)0.5:(Sm2O3)0.5 films were deposited on (001) oriented Nb-doped SrTiO3 substrates by pulsed laser deposition. The leakage current density versus electric field characteristics were investigated and compared with those of as-deposited and annealed pure BiFeO3 (BFO) thin films. The dominant leakage mechanisms of nanocomposite films were space-charge-limited current and Poole–Frenkle emission for positive and negative biases, respectively. The leakage current density of nanocomposite films was reduced three orders of magnitude in comparison with the as-deposited pure BFO films. The less oxygen vacancies in the BFO phase in the nanocomposite is believed to contribute to the leakage reduction.
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73.63.Bd Nanocrystalline materials
73.61.-r Electrical properties of specific thin films
73.50.Fq High-field and nonlinear effects
81.16.Mk Laser-assisted deposition
68.55.at Other materials
81.16.Dn Self-assembly
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Direct observation of the birth of a nanocrystalline nucleus in an amorphous matrix

Ijaz A. Rauf

Appl. Phys. Lett. 93, 143101 (2008); http://dx.doi.org/10.1063/1.2998256 (3 pages) | Cited 3 times

Online Publication Date: 6 October 2008

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Nucleation of crystals within an amorphous phase can be induced using electron beam irradiation in an electron microscope. In contrast to generally believed two-step phase transformation involving nucleation and growth, we observe a three-step transformation: a two-step nucleation stage followed by the growth process. The two steps in the nucleation stage are: the formation of a basic crystalline skeleton followed by the diffusion of excess defects to the periphery of the crystalline skeleton.
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81.07.Bc Nanocrystalline materials
64.60.Q- Nucleation
64.70.Nd Structural transitions in nanoscale materials
61.82.Rx Nanocrystalline materials
66.30.Pa Diffusion in nanoscale solids
64.70.K- Solid-solid transitions

Enhanced spontaneous emission in a photonic-crystal light-emitting diode

M. Francardi, L. Balet, A. Gerardino, N. Chauvin, D. Bitauld, L. H. Li, B. Alloing, and A. Fiore

Appl. Phys. Lett. 93, 143102 (2008); http://dx.doi.org/10.1063/1.2964186 (3 pages) | Cited 13 times

Online Publication Date: 6 October 2008

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We report direct evidence of enhanced spontaneous emission in a photonic-crystal (PhC) light-emitting diode. The device consists of p-i-n heterojunction embedded in a suspended membrane, comprising a layer of self-assembled quantum dots. Current is injected laterally from the periphery to the center of the PhC. A well-isolated emission peak at 1.3 μm from the PhC cavity mode is observed, and the enhancement of the spontaneous emission rate is clearly evidenced by time-resolved electroluminescence measurements, showing that our diode switches off in a time shorter than the bulk radiative and nonradiative lifetimes.
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85.60.Jb Light-emitting devices

Conducting polymer/carbon nanotube composite as counter electrode of dye-sensitized solar cells

Benhu Fan, Xiaoguang Mei, Kuan Sun, and Jianyong Ouyang

Appl. Phys. Lett. 93, 143103 (2008); http://dx.doi.org/10.1063/1.2996270 (3 pages) | Cited 40 times

Online Publication Date: 6 October 2008

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This letter reports dye-sensitized solar cells with a thin film of multiwall carbon nanotube/conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) composite as the counterelectrode. The composite thin film was prepared by spin coating the aqueous solution of the composite. The devices exhibited high performance with the energy conversion efficiency of 6.5%, short-circuit current of 15.5 mA cm−2, open-circuit voltage of 0.66 V, and fill factor of 0.63. This performance is close to the devices using conventional platinum as the counterelectrode and is significantly higher than the ones using a thin film of multiwall carbon nanotube/poly(styrenesulfonate acide) composite as the counterelectrode.
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84.60.Jt Photoelectric conversion

Electronically patterning through one-dimensional nanostripes with high density of states on single-crystalline Al2O3 domain

Pin-Jui Hsu, Chii-Bin Wu, Hong-Yu Yen, Sheng-Syun Wong, Wen-Chin Lin, and Minn-Tsong Lin

Appl. Phys. Lett. 93, 143104 (2008); http://dx.doi.org/10.1063/1.2996578 (3 pages) | Cited 3 times

Online Publication Date: 7 October 2008

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Self-assembled one-dimensional nanostripes on the single-crystalline Al2O3 domains are found to be the nucleation sites of nanoparticles through an enhanced density of states observed by the scanning tunneling microscopy and spectroscopy. Bias-dependent topographic images and the conductivity spectra indicate that these nanostripes have both enhanced occupied and unoccupied states within the oxide bandgap. These more metallic nanostripes have stronger electronically trapping ability than the oxide domain, which can be used as a one-dimensional electronically self-patterned template for the guided growth of nanostructures.
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81.07.Bc Nanocrystalline materials
81.16.Rf Micro- and nanoscale pattern formation
81.16.Dn Self-assembly
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.22.-f Electronic structure of nanoscale materials and related systems
73.63.Bd Nanocrystalline materials

Toward conductive traces: Dip Pen Nanolithography® of silver nanoparticle-based inks

Hung-Ta Wang, Omkar A. Nafday, Jason R. Haaheim, Emma Tevaarwerk, Nabil A. Amro, Raymond G. Sanedrin, Chih-Yang Chang, Fan Ren, and Stephen J. Pearton

Appl. Phys. Lett. 93, 143105 (2008); http://dx.doi.org/10.1063/1.2995859 (3 pages) | Cited 8 times

Online Publication Date: 7 October 2008

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Low cost, direct writing of conductive traces is highly desired for applications in nanoelectronics, photonics, circuit repair, flexible electronics, and nanoparticle-based gas detection. The unique ability of Dip Pen Nanolithography (DPN®) to direct write a variety of materials onto suitable surfaces with nanoscale resolution and area-specific patterning is leveraged in this work. We present a direct-write approach toward creating traces with commercially available silver nanoparticle (AgNP)-based inks using DPN. In this work we demonstrate submicron AgNP feature creation together with a discussion on the ink transport mechanism.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Rf Micro- and nanoscale pattern formation

Defect-free ZnSe nanowire and nanoneedle nanostructures

Thomas Aichele, Adrien Tribu, Catherine Bougerol, Kuntheak Kheng, Régis André, and Serge Tatarenko

Appl. Phys. Lett. 93, 143106 (2008); http://dx.doi.org/10.1063/1.2991298 (3 pages) | Cited 12 times

Online Publication Date: 7 October 2008

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We report the growth of ZnSe nanowires and nanoneedles using molecular beam epitaxy (MBE). Different growth regimes were found, depending on growth temperature and the Zn–Se flux ratio. By employing a combined MBE growth of nanowires and nanoneedles without any postprocessing of the sample, we achieved an efficient suppression of stacking fault defects. This is confirmed by transmission electron microscopy and by photoluminescence studies.
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81.07.Vb Quantum wires
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Et II-VI semiconductors
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)
61.72.Nn Stacking faults and other planar or extended defects

Differential surface stress sensor for detection of chemical and biological species

K. Kang, M. Nilsen-Hamilton, and P. Shrotriya

Appl. Phys. Lett. 93, 143107 (2008); http://dx.doi.org/10.1063/1.2996411 (3 pages) | Cited 2 times

Online Publication Date: 7 October 2008

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Show Abstract
We report a sensor consisting of two micromachined cantilevers (a sensing/reference pair) that is suitable for detection of chemical and biological species. The sensing strategy involves coating the sensing cantilever with receptors that have high affinities for the analyte. The presence of analyte is detected by determining the differential surface stress associated with its adsorption/absorption to the sensing cantilever. An interferometric technique is utilized to measure the differential bending of the sensing cantilever with respect to reference. Surface stress associated with hybridization of single stranded DNA is measured to demonstrate the unique advantages of the sensor.
Show PACS
87.85.fk Biosensors
82.80.-d Chemical analysis and related physical methods of analysis
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Cm Micromechanical devices and systems
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