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28 Jun 2010

Volume 96, Issue 26, Articles (26xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 261101 (2010); http://dx.doi.org/10.1063/1.3456618 (3 pages)

I. V. Konoplev, L. Fisher, A. W. Cross, A. D. R. Phelps, K. Ronald, and C. W. Robertson
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Surface wave Cherenkov maser based on a periodic lattice

I. V. Konoplev, L. Fisher, A. W. Cross, A. D. R. Phelps, K. Ronald, and C. W. Robertson

Appl. Phys. Lett. 96, 261101 (2010); http://dx.doi.org/10.1063/1.3456618 (3 pages) | Cited 4 times

Online Publication Date: 28 June 2010

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The excitation of a surface wave cavity based on a two-dimensional periodic structure by an energy source, such as relativistic electrons, results in stimulated, single frequency coherent emission. A high-Q cavity has been achieved via a resonant coupling between surface waves and volume waves. The concept of a Cherenkov maser based on the surface wave cavity is discussed and results of numerical studies presented. Links between the model described and the concept of a surface plasmon amplifier, which has been recently introduced are described.
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42.50.Pq Cavity quantum electrodynamics; micromasers
42.50.Wk Mechanical effects of light on material media, microstructures and particles

Free-standing AlxGa1−xAs heterostructures by gas-phase etching of germanium

Garrett D. Cole, Yu Bai, Markus Aspelmeyer, and Eugene A. Fitzgerald

Appl. Phys. Lett. 96, 261102 (2010); http://dx.doi.org/10.1063/1.3455104 (3 pages) | Cited 4 times

Online Publication Date: 28 June 2010

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We outline a facile fabrication technique for the realization of free-standing AlxGa1−xAs heterostructures of arbitrary aluminum content. Utilizing xenon difluoride (XeF2) we rapidly and selectively remove a sacrificial germanium (Ge) underlayer in a room temperature gas-phase etching procedure. We demonstrate two possibilities for exploiting this unique process: (1) bulk micromachining of a suspended high-frequency low-dissipation micro-optomechanical resonator consisting of an epitaxial GaAs/AlAs multilayer grown on a Ge substrate and (2) epitaxial lift-off of a GaAs film via removal of an embedded Ge sacrificial layer, resulting in lateral etch rates up to 3 mm/h and a conservative selectivity of ∼ 106.
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81.65.Cf Surface cleaning, etching, patterning
81.16.-c Methods of micro- and nanofabrication and processing
81.05.Ea III-V semiconductors
68.55.ag Semiconductors

Femtosecond laser near-field nanoablation patterning using Mie resonance high dielectric constant particle with small size parameter

Yuto Tanaka, Go Obara, Akira Zenidaka, Mitsuhiro Terakawa, and Minoru Obara

Appl. Phys. Lett. 96, 261103 (2010); http://dx.doi.org/10.1063/1.3458704 (3 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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We demonstrate near-field nanohole patterning using a Mie resonance, small size parameter particle for nanofabrication technology regardless of substrate’s refractive index. Maximal enhancement factor and nearly smallest spot diameter among the same size dielectric particles are simultaneously obtainable on both low-refractive-index SiO2 and high-refractive-index Si substrates with a 200 nm particle of magnetic quadrupole resonance scattering mode (n ∼ 2.7) at 400 nm excitation wavelength. Circular nanoholes with approximately 100 nm in diameter were fabricated on both substrates using a 200 nm amorphous TiO2 particle (n = 2.66+0.024i) even with lower laser fluences than a half ablation threshold of the bare substrates.
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79.20.Eb Laser ablation
81.16.Rf Micro- and nanoscale pattern formation

Reduction in the efficiency droop effect of a light-emitting diode through surface plasmon coupling

Chih-Feng Lu, Che-Hao Liao, Chih-Yen Chen, Chieh Hsieh, Yean-Woei Kiang, and C. C. Yang

Appl. Phys. Lett. 96, 261104 (2010); http://dx.doi.org/10.1063/1.3459151 (3 pages) | Cited 4 times

Online Publication Date: 30 June 2010

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The reduction in the external quantum efficiency (EQE) droop effect of an InGaN/GaN quantum-well (QW) light-emitting diode (LED) through the mechanism of surface plasmon (SP) coupling with QW is demonstrated. With a current spreading grid pattern on the mesa surface, a smaller grid period leads to more effective carrier transport into the QW regions of Ag deposition for stronger SP–QW coupling such that the droop effect is more significantly reduced, as indicated by the increase in injection current density of maximum EQE and the decrease in drooping slope. The claim of the SP–QW coupling effect in the samples of thin p-GaN is supported by the different droop behaviors of the LED samples fabricated with another epitaxial structure of thick p-GaN, in which the SP–QW coupling effect is expected to be weak.
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85.60.Jb Light-emitting devices
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.67.De Quantum wells

Enhancement of electroluminescence in GaN-based light-emitting diodes by metallic nanoparticles

Jun-Ho Sung, Jeong Su Yang, Bo-Soon Kim, Chul-Hyun Choi, Min-Woo Lee, Seung-Gol Lee, Se-Geun Park, El-Hang Lee, and Beom-Hoan O

Appl. Phys. Lett. 96, 261105 (2010); http://dx.doi.org/10.1063/1.3457349 (3 pages) | Cited 2 times

Online Publication Date: 1 July 2010

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The enhanced electroluminescence of GaN-based light-emitting diodes (LEDs) with noble metallic nanoparticles (MNPs) is demonstrated. The sample with well-designed Ag MNPs has shown the best performance enhancement of 126% in electroluminescent intensity compared with a conventional LED sample, even though the MNPs are placed at least 200 nm away from the quantum-well active layer. The MNPs provide enhanced photon scattering and coupling between localized surface plasmon resonance (LSPR) modes and photon modes internally trapped in a device. To investigate this effect, the peculiarities of the LSPR and the corresponding structural properties of the MNPs are discussed through the effective medium approach.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

High power single-lateral-mode operation of InAs quantum dot based ridge type laser diodes by utilizing a double bend waveguide structure

Kyoung Chan Kim, Il Ki Han, Jung Il Lee, and Tae Geun Kim

Appl. Phys. Lett. 96, 261106 (2010); http://dx.doi.org/10.1063/1.3459150 (3 pages)

Online Publication Date: 1 July 2010

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We report on the high-power, single-lateral-mode operation of InAs quantum dot (QD) based ridge type laser diodes (LDs) by utilizing a double bend (DB) waveguide structure. The LDs were designed so that only fundamental modes propagate and higher optical modes are suppressed through the bent regions. DB waveguide LDs allow the use of wide ridge widths for fundamental mode operations, which helps to increase their output power via the increase in their net gain. We measured continuous wave single-lateral-mode output power of up to 310 mW from InAs QD DB waveguide LDs manufactured with 10-μm-wide stripes without facet coating.
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42.55.Px Semiconductor lasers; laser diodes
68.65.Hb Quantum dots (patterned in quantum wells)
81.05.Ea III-V semiconductors
84.40.Az Waveguides, transmission lines, striplines

Geiger-mode operation of ultraviolet avalanche photodiodes grown on sapphire and free-standing GaN substrates

E. Cicek, Z. Vashaei, R. McClintock, C. Bayram, and M. Razeghi

Appl. Phys. Lett. 96, 261107 (2010); http://dx.doi.org/10.1063/1.3457783 (3 pages) | Cited 3 times

Online Publication Date: 1 July 2010

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GaN avalanche photodiodes (APDs) were grown on both conventional sapphire and low dislocation density free-standing (FS) c-plane GaN substrates. Leakage current, gain, and single photon detection efficiency (SPDE) of these APDs were compared. At a reverse-bias of 70 V, APDs grown on sapphire substrates exhibited a dark current density of 2.7×10−4 A/cm2 whereas APDs grown on FS-GaN substrates had a significantly lower dark current density of 2.1×10−6 A/cm2. Under linear-mode operation, APDs grown on FS-GaN achieved avalanche gain as high as 14 000. Geiger-mode operation conditions were studied for enhanced SPDE. Under front-illumination the 625-μm2-area APD yielded a SPDE of ∼ 13% when grown on sapphire substrates compared to more than 24% when grown on FS-GaN. The SPDE of the same APD on sapphire substrate increased to ∼ 30% under back-illumination—the FS-GaN APDs were only tested under front illumination due to the thick absorbing GaN substrate.
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85.60.Dw Photodiodes; phototransistors; photoresistors

Nanopyramid surface plasmon resonance sensors

Pei-Yu Chung, Tzung-Hua Lin, Gregory Schultz, Christopher Batich, and Peng Jiang

Appl. Phys. Lett. 96, 261108 (2010); http://dx.doi.org/10.1063/1.3460273 (3 pages) | Cited 5 times

Online Publication Date: 1 July 2010

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We report the achievement of sensitive chemical and biological sensing using periodic gold nanopyramids with nanoscale sharp tips created by a simple and scalable colloidal templating approach. The sharp tips and the long-range periodic structure of the nanopyramid arrays enable the excitement of both localized and propagating surface plasmons. The optical reflection and the detection sensitivity of the templated nanopyramid surface plasmon resonance sensors agree reasonably well with the theoretical predictions using a finite-difference time-domain model. We have also demonstrated that specific antigen-antibody binding can be detected by using nanopyramid arrays in a real-time and label-free manner.
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87.85.Rs Nanotechnologies-applications
87.80.-y Biophysical techniques (research methods)
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Effective light trapping in polycrystalline silicon thin-film solar cells by means of rear localized surface plasmons

Zi Ouyang, Supriya Pillai, Fiona Beck, Oliver Kunz, Sergey Varlamov, Kylie R. Catchpole, Patrick Campbell, and Martin A. Green

Appl. Phys. Lett. 96, 261109 (2010); http://dx.doi.org/10.1063/1.3460288 (3 pages) | Cited 20 times

Online Publication Date: 1 July 2010

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Significant photocurrent enhancement has been achieved for evaporated solid-phase-crystallized polycrystalline silicon thin-film solar cells on glass, due to light trapping provided by Ag nanoparticles located on the rear silicon surface of the cells. This configuration takes advantage of the high scattering cross-section and coupling efficiency of rear-located particles formed directly on the optically dense silicon layer. We report short-circuit current enhancement of 29% due to Ag nanoparticles, increasing to 38% when combined with a detached back surface reflector. Compared to conventional light trapping schemes for these cells, this method achieves 1/3 higher short-circuit current.
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88.40.H- Solar cells (photovoltaics)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Spatially resolved ultrafast transport current in GaAs photoswitches

L. Prechtel, S. Manus, D. Schuh, W. Wegscheider, and A. W. Holleitner

Appl. Phys. Lett. 96, 261110 (2010); http://dx.doi.org/10.1063/1.3458819 (3 pages) | Cited 2 times

Online Publication Date: 1 July 2010

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We apply a pump- and probe-scheme to coplanar stripline circuits to investigate the photocurrent response of GaAs photoswitches in time and space. We find a displacement current pulse, as reported earlier. We interpret a time-delayed second pulse as a transport current. In a time-of-flight analysis we determine the velocity of the photogenerated charge carriers in the transport current. It exceeds the Fermi and the single-particle quantum velocities. This suggests that the excitation of an electron-hole plasma and not single charge-carriers dominates the ultrafast transport current in GaAs photoswitches.
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85.60.-q Optoelectronic devices

Directional dependence of the second harmonic response in two-dimensional nonlinear photonic crystals

P. Molina, M. O. Ramírez, B. J. García, and L. E. Bausá

Appl. Phys. Lett. 96, 261111 (2010); http://dx.doi.org/10.1063/1.3459975 (3 pages) | Cited 6 times

Online Publication Date: 2 July 2010

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A two-dimensional periodic arrangement of alternating ferroelectric domains in LiNbO3, with asymmetric domain duty cycle has been used to demonstrate that counterpropagating beams along the polar axis can generate disparate second harmonic patterns, which are nonsymmetrical with respect to the source and the point of observation. These findings provide alternative routes to generate dissimilar light-matter interaction processes in two-dimensional structures assembled onto polar surfaces, including metals for plasmonics or biological compounds.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Qs Photonic bandgap materials
77.80.Dj Domain structure; hysteresis
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Heating dynamics and extreme ultraviolet radiation emission of laser-produced Sn plasmas

S. Yuspeh, K. L. Sequoia, Y. Tao, M. S. Tillack, R. A. Burdt, and F. Najmabadi

Appl. Phys. Lett. 96, 261501 (2010); http://dx.doi.org/10.1063/1.3458696 (3 pages) | Cited 2 times

Online Publication Date: 30 June 2010

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The impact of 1.064 μm laser absorption depth on the heating and in-band (2% bandwidth) 13.5 nm extreme ultraviolet emissions in Sn plasmas is investigated experimentally and numerically. In-band emission lasting longer than the laser pulse and separation between the laser absorption and in-band emission region are observed. Maximum efficiency is achieved by additional heating of the core of the plasma to allow the optimal temperature to expand to a lower and more optically thin density. This leads to higher temperature plasma that emits less in-band light as compared to CO2 produced plasma sources for the same application.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.50.Dg Plasma sources
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Size controlled synthesis of Ge nanocrystals in SiO2 at temperatures below 400 °C using magnetron sputtering

B. Zhang, S. Shrestha, M. A. Green, and G. Conibeer

Appl. Phys. Lett. 96, 261901 (2010); http://dx.doi.org/10.1063/1.3457864 (3 pages) | Cited 6 times

Online Publication Date: 28 June 2010

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A simple and silicon process-compatible technique is reported for the synthesis of Ge nanocrystals (Ge-ncs) at low temperatures below 400 °C, which is much lower than the typical growth temperatures. The Ge-ncs were found to form only within a temperature window between 350 and 420 °C. The underlying mechanism has been explained by a competitive process between Volmer–Weber growth and oxidation reaction. We further implemented this technique in the fabrication of multilayered Ge-ncs which exhibited controllable crystallite size with high crystallization quality. The low temperature technique developed in this work would allow production of Ge-ncs and relative devices on low cost substrates, such as glass.
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81.07.Bc Nanocrystalline materials
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
81.65.Mq Oxidation
68.65.Ac Multilayers
82.45.Yz Nanostructured materials in electrochemistry

Diaspore crystal structure and compressibility at high pressures and high temperature

Ming Li, Karim Snoussi, Lixin Li, Huixin Wang, Wuming Yang, and Chunxiao Gao

Appl. Phys. Lett. 96, 261902 (2010); http://dx.doi.org/10.1063/1.3457919 (3 pages)

Online Publication Date: 28 June 2010

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We have determined the unit-cell parameters of diaspore α-AlO(OH) at high pressures (13.5–27.8 GPa) and at high temperature (1900 K). Experimental data are compared with the theoretically predicted crystal structure variations derived from density functional theory (DFT) calculations. The experimental analysis establishes that the a axial direction is more compressible than the b and c axial directions in the low-pressure range (13.5–18 GPa) and at 1900 K, whereas all three directions show similar behaviors in the high-pressure range (18–27.8 GPa). The diaspore isothermal bulk modulus KT values are 137.6 GPa, 124.8 GPa, and 141.3 GPa, respectively, at 300 K, at 1900 K, and again at 300 K after quenching. By comparison, the diaspore isothermal bulk modulus KT computed at 300 K and at ambient pressure in the framework of the plane-wave pseudopotential approach is equal to 129.3 GPa.
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81.40.Lm Deformation, plasticity, and creep
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
81.40.Gh Other heat and thermomechanical treatments

In situ evolution of stress gradients in Cu films induced by capping layers

Conal E. Murray, Paul R. Besser, Christian Witt, and Michael Toney

Appl. Phys. Lett. 96, 261903 (2010); http://dx.doi.org/10.1063/1.3458864 (3 pages)

Online Publication Date: 29 June 2010

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Depth-dependent stress distributions within copper films possessing capping layers were measured during in situ thermal anneals. Glancing-incidence x-ray diffraction measurements of SiCxNyHz capped Cu films revealed that a strain gradient near the cap/Cu interface, created by constraint imposed by the cap during its deposition process, decreased as the sample temperature increased to 350 °C. Although the increase in sample temperature allowed Cu to approach its equilibrium lattice spacing at the cap deposition temperature and minimize the corresponding stress gradient, both the gradient and concomitant increase in residual bulk stress of the Cu film reappeared after cooling to room temperature.
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85.40.Ls Metallization, contacts, interconnects; device isolation
68.60.-p Physical properties of thin films, nonelectronic
68.55.at Other materials

Composition measurement of the Ni-silicide transient phase by atom probe tomography

K. Hoummada, I. Blum, D. Mangelinck, and A. Portavoce

Appl. Phys. Lett. 96, 261904 (2010); http://dx.doi.org/10.1063/1.3457995 (3 pages) | Cited 3 times

Online Publication Date: 29 June 2010

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The transient phase observed during the reaction of a Ni(Pt) alloy with a (001)Si substrate is studied using in situ x-ray diffraction and atom probe tomography microscopy. This transient phase exhibits a diffraction peak at 47°, and is found to have a uniform composition corresponding to Ni0.6Si0.4. During the reaction, it is located between a δ-Ni2Si layer and a thin (nanocrystalline or amorphous) NiSi layer in contact with Si. The Pt atoms are found in the δ-Ni2Si grain boundaries, while they have not been detected in the NiSi layer.
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68.35.Fx Diffusion; interface formation
82.80.-d Chemical analysis and related physical methods of analysis
61.72.Mm Grain and twin boundaries
68.55.at Other materials

Evidence of graphene-like electronic signature in silicene nanoribbons

Paola De Padova, Claudio Quaresima, Carlo Ottaviani, Polina M. Sheverdyaeva, Paolo Moras, Carlo Carbone, Dinesh Topwal, Bruno Olivieri, Abdelkader Kara, Hamid Oughaddou, Bernard Aufray, and Guy Le Lay

Appl. Phys. Lett. 96, 261905 (2010); http://dx.doi.org/10.1063/1.3459143 (3 pages) | Cited 23 times

Online Publication Date: 30 June 2010

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We report on the electronic properties of straight, 1.6 nm wide, silicene nanoribbons on Ag(110), arranged in a one-dimensional grating with a pitch of 2 nm, whose high-resolution scanning tunneling microscopy images reveal a honeycomb geometry. Angle-resolved photoemission shows quantum confined electronic states of one-dimensional character. The silicon band dispersion along the direction of the nanoribbons suggests a behavior analogous to the Dirac cones of graphene on different substrates.
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73.22.-f Electronic structure of nanoscale materials and related systems
61.46.-w Structure of nanoscale materials
79.60.Jv Interfaces; heterostructures; nanostructures

MN+1AXN(M = Ti,A = Al,X = H) phase class materials with hydrogen: Ti4AlH3 and Ti3AlH2

M. Ramzan and R. Ahuja

Appl. Phys. Lett. 96, 261906 (2010); http://dx.doi.org/10.1063/1.3459960 (3 pages) | Cited 2 times

Online Publication Date: 30 June 2010

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To date more than 50 MAX phases known to exist but all of those are consist of nitrides or carbides. We present a modified type of these phases, Ti4AlH3 and Ti3AlH2, having hydrides in their composition, by our density functional theory (DFT) calculations. We study the structural stability, electronic structure, elastic, thermal, and mechanical properties of these materials which are comparable with well known phases: Ti3SiC2, Ti4AlN3, and Ti3AlC2. Moreover, these materials can also be studied for hydrogen storage purposes. We hope that our work will be helpful to discover the other types of such phases which are important from the technological and industrial point of view.
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62.20.de Elastic moduli
62.20.-x Mechanical properties of solids
65.40.-b Thermal properties of crystalline solids
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.66.Fn Inorganic compounds

Magnified hard x-ray image in one dimension

James Britten, Zhechuan Feng, and Gu Xu

Appl. Phys. Lett. 96, 261907 (2010); http://dx.doi.org/10.1063/1.3459969 (3 pages)

Online Publication Date: 30 June 2010

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The possibility of magnified x-ray imaging is explored, by the near-field attenuation of a sample intercepting a spherical wave-front, plus the beam profile modulation by Borrmann pyramid based on dynamic x-ray scattering. It is verified by experiments in one dimension as well as numerical simulation.
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07.85.-m X- and γ-ray instruments

Optical switching of a metamaterial by temperature controlling

Wan-xia Huang, Xiao-gang Yin, Cheng-ping Huang, Qian-jin Wang, Teng-fei Miao, and Yong-yuan Zhu

Appl. Phys. Lett. 96, 261908 (2010); http://dx.doi.org/10.1063/1.3458706 (3 pages) | Cited 3 times

Online Publication Date: 2 July 2010

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We have fabricated a metamaterial of metal/semiconductor/metal sandwich nanostrips structure comprising a pair of gold strips and a vanadium dioxide (VO2) strip. The optical response of the metamaterial has been studied. The results indicate the nanostructure with VO2 strips can be used as a temperature-controlling optical switch and the mechanism of this switch can be explained by the magnetic resonance.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.70.-a Optical materials
81.16.-c Methods of micro- and nanofabrication and processing
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
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Band alignment at Sb2S3/Cu(In,Ga)Se2 heterojunctions and electronic characteristics of solar cell devices based on them

D. Kieven, A. Grimm, I. Lauermann, T. Rissom, and R. Klenk

Appl. Phys. Lett. 96, 262101 (2010); http://dx.doi.org/10.1063/1.3457439 (3 pages) | Cited 2 times

Online Publication Date: 28 June 2010

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Band offsets at Sb2S3/Cu(In,Ga)Se2 heterojunctions have been studied by x-ray and ultraviolet photoemission spectroscopy. The valence and conduction band offset have been estimated to −(0.6±0.3) eV and (0.2±0.3) eV, respectively. This result suggests Sb2S3 as a potential buffer layer material for chalcopyrite based solar cells. However, Cu(In,Ga)Se2/Sb2S3/ZnO solar cells have been investigated. While the open circuit voltage ranged up to ∼ 0.4–0.5 V, the short circuit current was limited to ∼ 1.8–4.9 mA/cm2. A photocurrent of about 30 mA/cm2 was found for negative bias. On the basis of bias dependent quantum efficiency measurements and calculations, limiting mechanisms are discussed.
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88.40.H- Solar cells (photovoltaics)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.60.-i Photoemission and photoelectron spectra

Growth, electrical rectification, and gate control in axial in situ doped p-n junction germanium nanowires

Son T. Le, P. Jannaty, A. Zaslavsky, S. A. Dayeh, and S. T. Picraux

Appl. Phys. Lett. 96, 262102 (2010); http://dx.doi.org/10.1063/1.3457862 (3 pages) | Cited 3 times

Online Publication Date: 28 June 2010

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We report on vapor-liquid-solid growth and electrical properties of axial in situ doped p-n junction Ge sub-100 nm diameter nanowires. Room temperature four-point measurements show current rectification of two to three orders of magnitude depending on nanowire doping and diameter. We observe strong backgate control of reverse-bias current of up to three orders of magnitude and explain it by band-to-band tunneling modulated by the backgate-controlled electric field, as confirmed qualitatively via a quasi-three-dimensional Schrödinger–Poisson simulation.
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68.65.La Quantum wires (patterned in quantum wells)
81.07.Gf Nanowires
61.72.U- Doping and impurity implantation
85.40.Ry Impurity doping, diffusion and ion implantation technology
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

High thermoelectric power factor in Fe-substituted Mo3Sb7

C. Candolfi, B. Lenoir, A. Dauscher, B. Malaman, E. Guilmeau, J. Hejtmanek, and J. Tobola

Appl. Phys. Lett. 96, 262103 (2010); http://dx.doi.org/10.1063/1.3457920 (3 pages) | Cited 1 time

Online Publication Date: 28 June 2010

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Thermoelectric properties of the Mo2.57Fe0.43Sb7 compound, a ternary derivative of Mo3Sb7, are reported from 2 up to 1000 K. Even though Fe substitution keeps low electrical resistivity values, high thermopower values are achieved at high temperatures. Electronic band structure calculations show that the high thermopower observed arises from the beneficial influence of iron d-states contribution to the density of states at the Fermi level. A high power factor similar to those of the best state-of-the-art thermoelectric materials emerges which, coupled with magnetic excitations that help to keep very low thermal conductivity values, leads to a dimensionless thermoelectric figure of merit of 0.55 at 1000 K.
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72.15.Jf Thermoelectric and thermomagnetic effects
71.20.-b Electron density of states and band structure of crystalline solids
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)

Bias-induced oxygen adsorption in zinc tin oxide thin film transistors under dynamic stress

Yu-Chun Chen, Ting-Chang Chang, Hung-Wei Li, Shih-Ching Chen, Jin Lu, Wan-Fang Chung, Ya-Hsiang Tai, and Tseung-Yuen Tseng

Appl. Phys. Lett. 96, 262104 (2010); http://dx.doi.org/10.1063/1.3457996 (3 pages) | Cited 12 times

Online Publication Date: 28 June 2010

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This study investigates the effects of bias-induced oxygen adsorption on the electrical characteristic instability of zinc tin oxide thin film transistors in different ambient oxygen partial pressures. When oxygen pressure is largest, the threshold voltages showed the quickest increase but the slowest recovery during the stress phase and recovery phase, respectively. This finding corresponds to the charge trapping time constant and recovery time constant, which are extracted by fitting the stretched-exponential equation and which exhibit a relationship with oxygen pressure. We suggest that the gate bias reduces the activation energy of oxygen adsorption during gate bias stress.
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85.30.Tv Field effect devices
68.55.ag Semiconductors

Intrinsic carrier mobility in amorphous In–Ga–Zn–O thin-film transistors determined by combined field-effect technique

Mutsumi Kimura, Toshio Kamiya, Takashi Nakanishi, Kenji Nomura, and Hideo Hosono

Appl. Phys. Lett. 96, 262105 (2010); http://dx.doi.org/10.1063/1.3455072 (3 pages) | Cited 8 times

Online Publication Date: 29 June 2010

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Amorphous In–Ga–Zn–O (α-IGZO) is expected for thin-film transistors (TFTs) in next-generation flat-panel displays but its intrinsic properties are not understood well and different mobility models have been applied to different films. This letter reports that a universal mobility model is obtained using a field-effect technique and capacitance-voltage method. Electrical characteristics of α-IGZO TFTs subjected to different annealing are reproduced using the mobility model and different trap densities. The present achievement will be a necessary basis to establish device and circuit simulators for α-IGZO-based electronic applications.
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85.30.Tv Field effect devices
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  2. Magnetic metal cladding gives better attenuation in small waveguides operating at high microwave frequencies than nonmagnetic metals
  3. The structure and growth direction of rare earth silicide nanowires on Si(100)
  4. Influence of index contrast in two dimensional photonic crystal lasers
  5. Upconversion of a relativistic Coulomb field terahertz pulse to the near infrared
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