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2 Jan 2012

Volume 100, Issue 1, Articles (01xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 013101 (2012); http://dx.doi.org/10.1063/1.3673334 (3 pages)

Patrice Genevet, Nanfang Yu, Francesco Aieta, Jiao Lin, Mikhail A. Kats, Romain Blanchard, Marlan O. Scully, Zeno Gaburro, and Federico Capasso
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Announcement: Celebration of Applied Physics Letters’ fiftieth anniversary with revision of the table of contents and increased article length limit

Nghi Q. Lam

Appl. Phys. Lett. 100, 010201 (2012); http://dx.doi.org/10.1063/1.3676066 (1 page)

Online Publication Date: 3 January 2012

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01.10.Cr Announcements, news, and awards
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Super-resolution spatial frequency differentiation of nanoscale particles with a vibrating nanograting

Leonid Alekseyev, Evgenii Narimanov, and Jacob Khurgin

Appl. Phys. Lett. 100, 011101 (2012); http://dx.doi.org/10.1063/1.3673470 (3 pages) | Cited 1 time

Online Publication Date: 3 January 2012

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We propose a scheme for detecting and differentiating deeply subwavelength particles based on their spatial features. Our approach combines scattering from an ultrasonically modulated nanopatterned grating with heterodyne techniques to enable far-field detection of high spatial frequency Fourier components. Our system is sensitive to spatial features commensurate in size to the patterning scale of the grating. We solve the scattering problem in Born approximation and illustrate the dependence of the signal amplitude at modulation frequency on grating period, which allows to differentiate between model nanoparticles of size λ/20.
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42.30.Sy Pattern recognition
42.79.Dj Gratings

Modulation of surface plasmon wave by photo-induced refractive index changes of CdSe quantum dots

Horng-Shyang Chen, Jyh-Yang Wang, Sheng-Shiuan Yeh, Chii-Dong Chen, and Hung-Yi Lin

Appl. Phys. Lett. 100, 011102 (2012); http://dx.doi.org/10.1063/1.3673560 (3 pages)

Online Publication Date: 3 January 2012

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We demonstrate an all-optical modulation of surface plasmon resonance by photo-irradiation induced dielectric constant change of CdSe quantum dots on the gold surface. The dipole-dipole interaction between the surface plasmon and the photo-induced excitons in the dots gives rise to a shift in the surface plasmon resonance peak. This shift is found to sensitively reflect a tiny change in the dielectric constant, which is useful for investigating the nonlinear effect in active plasmonic components.
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78.67.Hc Quantum dots
73.43.Lp Collective excitations
73.21.La Quantum dots
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations

Single lateral mode mid-infrared laser diode using wavelength-scale modulation of the facet reflectivity

G. R. Nash, J. L. Stokes, J. R. Pugh, S. J. B. Przeslak, P. J. Heard, J. G. Rarity, and M. J. Cryan

Appl. Phys. Lett. 100, 011103 (2012); http://dx.doi.org/10.1063/1.3673824 (3 pages)

Online Publication Date: 3 January 2012

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The characteristics of mid-infrared laser diodes have been investigated before and after the patterning of wavelength-scale metallic apertures on the emitting facet. Before modification of the facet, the emitted spectrum consisted of a large number of peaks associated with different spatial modes, whereas afterwards, the spectrum was dominated by a single peak. Simulations showed that the patterning of the facet caused the effective reflectivity to be different for each lateral mode, suggesting that the peak in the measured spectra is associated with the single lateral mode which is most strongly reflected from the modified facet.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Implementation of a semi-transparent mid-infrared quantum well infrared photodetector simultaneously as a beamsplitter and a reference detector

Ekua N. Bentil, Germano M. Penello, William O. Charles, Peter Q. Liu, and Claire F. Gmachl

Appl. Phys. Lett. 100, 011104 (2012); http://dx.doi.org/10.1063/1.3673835 (3 pages) | Cited 1 time

Online Publication Date: 4 January 2012

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We demonstrate a dual purpose quantum well infrared photodetector (QWIP) useful in laser-based gas sensing systems. This photodetector functions simultaneously as a beamsplitter and a photodetector. By varying the incidence angle and light polarization, the QWIP has the ability to reflect, absorb, and transmit varying percentages of the incident mid-infrared light. At 45° incidence angle, ∼25% of a transverse magnetic polarized light is reflected, ∼16% is transmitted, and ∼59% is absorbed by the QWIP (at 80 K). The absorbed and transmitted signals are useful as reference signals for laser source monitoring and stabilizing. The reflected signal remains available as the primary beam.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Fm Reflectors, beam splitters, and deflectors
42.25.Ja Polarization
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Practicality of compensating the loss in the plasmonic waveguides using semiconductor gain medium

Jacob B. Khurgin and Greg Sun

Appl. Phys. Lett. 100, 011105 (2012); http://dx.doi.org/10.1063/1.3673849 (3 pages) | Cited 9 times

Online Publication Date: 4 January 2012

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We consider the issue of compensating the loss in plasmonic waveguides with semiconductor gain material and show that, independent of specific geometry, full loss compensation in plasmonic waveguides with significantly sub-wavelength light confinement (less than λ/4n) requires current density well in excess of 100 kA/cm2. This high current density is attributed to the unavoidable shortening of recombination time caused by the Purcell effect inherent to sub-wavelength confinement. Consequently, an injection-pumped plasmonic laser that is truly sub-wavelength in all three dimensions (“spaser”) would have threshold current densities that are hard to obtain in any conceivable semiconductor device.
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42.79.Gn Optical waveguides and couplers
78.66.Bz Metals and metallic alloys
78.67.De Quantum wells

High data-rate atom interferometer for measuring acceleration

Hayden J. McGuinness, Akash V. Rakholia, and Grant W. Biedermann

Appl. Phys. Lett. 100, 011106 (2012); http://dx.doi.org/10.1063/1.3673845 (4 pages) | Cited 5 times

Online Publication Date: 5 January 2012

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We demonstrate a high data-rate light-pulse atom interferometer for measuring acceleration. The device is optimized to operate at rates between 50 Hz to 330 Hz with sensitivities of 0.57μg/math to 36.7μg/math, respectively. Our method offers a dramatic increase in data rate and demonstrates a path to applications in highly dynamic environments. The performance of the device can largely be attributed to the high recapture efficiency of atoms from one interferometer measurement cycle to another.
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03.75.Dg Atom and neutron interferometry
03.75.Be Atom and neutron optics
06.30.Gv Velocity, acceleration, and rotation

Terahertz scattering by granular composite materials: An effective medium theory

Mayank Kaushik, Brian W.-H. Ng, Bernd M. Fischer, and Derek Abbott

Appl. Phys. Lett. 100, 011107 (2012); http://dx.doi.org/10.1063/1.3674289 (3 pages) | Cited 1 time

Online Publication Date: 5 January 2012

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Terahertz (THz) spectroscopy and imaging have emerged as important tools for identification and classification of various substances, which exhibit absorption characteristics at distinct frequencies in the THz range. The spectral fingerprints can potentially be distorted or obscured by electromagnetic scattering caused by the granular nature of some substances. In this paper, we present THz time domain transmission measurements of granular polyethylene powders in order to investigate an effective medium theory that yields a parameterized model, which can be used to estimate the empirical measurements to good accuracy.
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78.70.Gq Microwave and radio-frequency interactions

Effects of stimulated emission on transport in terahertz quantum cascade lasers based on diagonal designs

I. Bhattacharya, C. W. I. Chan, and Q. Hu

Appl. Phys. Lett. 100, 011108 (2012); http://dx.doi.org/10.1063/1.3675452 (3 pages) | Cited 4 times

Online Publication Date: 6 January 2012

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A hybrid Monte Carlo-density matrix transport simulator is used to analyze the transport properties of resonant-phonon type terahertz quantum cascade lasers. By comparing calculated and experimental results, the importance of stimulated emission to the interpretation of experimental data is highlighted, particularly for devices based on diagonal radiative transitions. Finally, we discuss the absence of mode competition effects on transport.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
84.40.-x Radiowave and microwave (including millimeter wave) technology

Impact of luminescence quenching on relaxation-oscillation frequency in solid-state lasers

Laura Agazzi, Edward H. Bernhardi, Kerstin Wörhoff, and Markus Pollnau

Appl. Phys. Lett. 100, 011109 (2012); http://dx.doi.org/10.1063/1.3674312 (3 pages) | Cited 2 times

Online Publication Date: 6 January 2012

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Measurement of the laser relaxation-oscillation frequency as a function of pump rate allows one to determine parameters of the laser medium or cavity. We show that luminescence quenching of a fraction of the rare-earth ions in a solid-state laser affects the relaxation oscillations, resulting in incorrect values for the parameter deduced from this measurement. In the equations describing the relaxation oscillations, we replace the lifetime of the upper laser level by an effective lifetime that takes the luminescence quenching into account. In an Al2O3:Yb3+ distributed-feedback laser we observe significant quenching, with the effective lifetime being ∼18 times shorter than the intrinsic upper-laser-level lifetime.
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07.60.-j Optical instruments and equipment
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
06.30.Ft Time and frequency

Leaky-mode effects in plasmonic-coupled quantum dot infrared photodetectors

S. C. Lee, Y. D. Sharma, S. Krishna, and S. R. J. Brueck

Appl. Phys. Lett. 100, 011110 (2012); http://dx.doi.org/10.1063/1.3675335 (3 pages) | Cited 1 time

Online Publication Date: 6 January 2012

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The effects of a heavily doped GaAs top contact layer on a plasmonics-integrated InAs quantum dot infrared photodetector (QDIP) are investigated. A metal photonic crystal (MPC), a 100 nm-thick gold film perforated with a 2.5 μm-period, 2-dimensional square hole array, is employed as a plasmonic coupler. The MPC is fabricated on QDIPs with identical structures except for the thickness (0.1 and 1.3 μm) of the top contact layer (doping concentration ∼2 × 1018 cm−3). For the lowest order surface plasma wave (SPW) resonance, the resonance wavelength undergoes a blue shift of 0.27 μm from 8.26 μm, and the responsivity and detectivity drop by ∼50% for the thicker contact layer. These effects are explained by leaky mode characteristics resulting from the free-carrier-reduced dielectric constant in the contact region that impacts the SPW resonance.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
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Probing dusty-plasma/surface interactions with a heat flux microsensor

S. N. Abolmasov, P. A. Cormier, A. Torres Rios, R. Dussart, N. Semmar, A. L. Thomann, and P. Roca i Cabarrocas

Appl. Phys. Lett. 100, 011601 (2012); http://dx.doi.org/10.1063/1.3674290 (3 pages) | Cited 1 time

Online Publication Date: 4 January 2012

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Heat flux microsensor—a thermopile with millisecond response time—was employed for direct measurements of total energy flux to a floated surface in a dusty rf discharge. The measurements were performed in silane-hydrogen plasmas at discharge conditions close to those used for the growth of polymorphous silicon films. At rf power between 10 and 50 W, the measured energy flux was in the range of 20-250 mW/cm2. Due to fast time response, the thermopile was also capable of tracing the dynamics of nanoparticle growth. A significant decrease (about 30%) in the energy flux was observed during the agglomeration phase.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.80.Pi High-frequency and RF discharges
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Cm Micromechanical devices and systems
52.27.Lw Dusty or complex plasmas; plasma crystals
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Growth, optical, and electrical properties of nonpolar m-plane ZnO on p-Si substrates with Al2O3 buffer layers

T. Wang, H. Wu, C. Chen, and C. Liu

Appl. Phys. Lett. 100, 011901 (2012); http://dx.doi.org/10.1063/1.3673346 (3 pages) | Cited 8 times

Online Publication Date: 3 January 2012

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Nonploar m-plane ZnO films were grown on p-Si (111) substrates by using atomic layer deposition. X-ray diffraction and high resolution tunneling electron microscopy measurements showed that the ZnO films were 〈10math0〉 oriented, and the crystalline quality of ZnO films was improved with an Al2O3 buffer layer, which significantly enhances the photoluminescence and reduces the reverse leakage current of ZnO/Si heterojuction.
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68.55.ag Semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.hf ZnO
78.55.-m Photoluminescence, properties and materials
78.66.-w Optical properties of specific thin films
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Temperature dependence of the thermal boundary resistivity of glass-embedded metal nanoparticles

Francesco Banfi, Vincent Juvé, Damiano Nardi, Stefano Dal Conte, Claudio Giannetti, Gabriele Ferrini, Natalia Del Fatti, and Fabrice Vallée

Appl. Phys. Lett. 100, 011902 (2012); http://dx.doi.org/10.1063/1.3673559 (3 pages) | Cited 3 times

Online Publication Date: 3 January 2012

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The temperature dependence of the thermal boundary resistivity is investigated in glass-embedded Ag particles of radius 4.5 nm, in the temperature range from 300 to 70 K, using all-optical time-resolved nanocalorimetry. The present results provide a benchmark for theories aiming at explaining the thermal boundary resistivity at the interface between metal nanoparticles and their environment, a topic of great relevance when tailoring thermal energy delivery from nanoparticles as for applications in nanomedicine and thermal management at the nanoscale.
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66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
78.67.Sc Nanoaggregates; nanocomposites
78.47.D- Time resolved spectroscopy (>1 psec)
68.35.Ja Surface and interface dynamics and vibrations
61.46.-w Structure of nanoscale materials
81.16.-c Methods of micro- and nanofabrication and processing

Large thermal Hall coefficient in bismuth

W. Kobayashi, Y. Koizumi, and Y. Moritomo

Appl. Phys. Lett. 100, 011903 (2012); http://dx.doi.org/10.1063/1.3673562 (3 pages)

Online Publication Date: 4 January 2012

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We present a systematical study of thermal Hall effect on a bismuth single crystal by measuring resistivity, Hall coefficient, and thermal conductivity under magnetic field, which shows a large thermal Hall coefficient comparable to the largest one in a semiconductor HgSe. We discuss that this is mainly due to a large mobility and a low thermal conductivity comparing theoretical calculations, which will give a route for controlling heat current in electronic devices.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
66.70.Df Metals, alloys, and semiconductors

Metamaterial with mass-stem array in acoustic cavity

Md Tofiqul Islam and Golam Newaz

Appl. Phys. Lett. 100, 011904 (2012); http://dx.doi.org/10.1063/1.3673833 (3 pages) | Cited 2 times

Online Publication Date: 4 January 2012

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A vibro-acoustic metamaterial with negative effective mass has been designed and fabricated. This metamaterial consists of an array of wire stems with attached tiny masses in an acoustic cavity. These internal masses contribute to energy absorption near the natural frequencies of the designed structure. This metamaterial damps single resonance of internal mass and has larger mass damping parameter than stiffness damping parameter. Ease of fabrication makes the metamaterial practical for dynamic disturbance mitigation and acoustic attenuation.
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43.20.-f General linear acoustics
62.65.+k Acoustical properties of solids

Molecular beam epitaxial growth and optical properties of highly mismatched ZnTe1−xOx alloys

Tooru Tanaka, Shuhei Kusaba, Tomohiro Mochinaga, Katsuhiko Saito, Qixin Guo, Mitsuhiro Nishio, Kin M. Yu, and Wladek Walukiewicz

Appl. Phys. Lett. 100, 011905 (2012); http://dx.doi.org/10.1063/1.3674310 (3 pages) | Cited 5 times

Online Publication Date: 4 January 2012

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Highly mismatched ZnTe1−xOx(ZnTeO) alloys have been grown by molecular beam epitaxy. X-ray diffraction (XRD) analyses showed that a single-phase ZnTeO layer were grown with a substitutional O composition x up to 1.34% on ZnTe(001) substrate in this experiments. Optical transitions associated with the lower (E−) and upper (E+) conduction subbands resulting from the anticrossing interaction between the localized O states and the extended conduction states of ZnTe were clearly observed, and the dependence of the energy position of these bands on the O composition was consistent with the band anticrossing model.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
78.66.Li Other semiconductors
71.20.Nr Semiconductor compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Growth temperature dependence of exciton lifetime in wurtzite InP nanowires grown on silicon substrates

N. Chauvin, M. H. Hadj Alouane, R. Anufriev, H. Khmissi, K. Naji, G. Patriarche, C. Bru-Chevallier, and M. Gendry

Appl. Phys. Lett. 100, 011906 (2012); http://dx.doi.org/10.1063/1.3674985 (4 pages) | Cited 6 times

Online Publication Date: 4 January 2012

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InP nanowires grown on silicon substrate are investigated using time-resolved spectroscopy. A strong modification of the exciton lifetime is observed (from 0.11 to 1.2 ns) when the growth temperature is increased from 340 °C to 460 °C. This strong dependence is not related to the density of zinc-blende insertions in the wurtzite nanowires or to the wurtzite exciton linewidth. The excitation power dependence of the lifetime and linewidth is investigated, and these results allow us to interpret the growth temperature dependence on the lifetime as a consequence of the reduction of the surface recombination velocity with the growth temperature.
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81.16.-c Methods of micro- and nanofabrication and processing
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.35.-y Excitons and related phenomena
78.47.D- Time resolved spectroscopy (>1 psec)
81.07.Gf Nanowires
81.05.Ea III-V semiconductors

Isothermal crystallization of poly(3-hydroxybutyrate) studied by terahertz two-dimensional correlation spectroscopy

Hiromichi Hoshina, Shinya Ishii, Yusuke Morisawa, Harumi Sato, Isao Noda, Yukihiro Ozaki, and Chiko Otani

Appl. Phys. Lett. 100, 011907 (2012); http://dx.doi.org/10.1063/1.3673847 (3 pages)

Online Publication Date: 5 January 2012

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The isothermal crystallization of poly(3-hydroxybutylate) (PHB) was studied by monitoring the temporal evolution of terahertz absorption spectra in conjunction with spectral analysis using two-dimensional correlation spectroscopy. Correlation between the absorption peaks and the sequential order of the changes in spectral intensity extracted from synchronous and asynchronous plots indicated that crystallization of PHB at 90 °C is a two step process, in which C-H···O=C hydrogen bonds are initially formed before well-defined crystal structures are established.
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64.70.km Polymers
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.70.Gq Microwave and radio-frequency interactions
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
78.40.Me Organic compounds and polymers
78.30.Jw Organic compounds, polymers

Photo-assisted bistable switching using Mott transition in two-terminal VO2 device

Giwan Seo, Bong-Jun Kim, Yong Wook Lee, and Hyun-Tak Kim

Appl. Phys. Lett. 100, 011908 (2012); http://dx.doi.org/10.1063/1.3672812 (3 pages) | Cited 4 times

Online Publication Date: 5 January 2012

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In order to investigate bistable switching characteristics of planar junction devices based on vanadium dioxide (VO2) thin films, we have measured the optical power dependence of the threshold voltage of the device, at which a current jump, regarded as the Mott metal-insulator transition (MIT), happened, by using an infrared laser with a wavelength of ∼1.55 μm, illuminated onto the VO2 film. In a test closed loop circuit connecting a DC voltage source, a standard resistor, and a VO2 thin film device in series, the bistability of the voltage across the device (VD) was examined with respect to a variety of illumination powers (PLs). By triggering the forward or reverse phase transition (Mott MIT) of the VO2 film with “SET” or “RESET” optical pulse, respectively, the photo-assisted bistable switching of VD in the test circuit properly DC biased could be realized at an intermediate PL chosen between optical powers of “SET” and “RESET” pulses. In particular, the transient response of VD showed not only bistable states of VD but also their switching speed.
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84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)

Orientation dependence of polarized Raman spectroscopy for nonpolar, semi-polar, and polar bulk GaN substrates

Bei Ma, Daiki Jinno, Hideto Miyake, Kazumasa Hiramatsu, and Hiroshi Harima

Appl. Phys. Lett. 100, 011909 (2012); http://dx.doi.org/10.1063/1.3674983 (3 pages) | Cited 1 time

Online Publication Date: 5 January 2012

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Polarized Raman spectroscopy has been performed on high-quality bulk gallium nitride substrates with various crystal orientations. The transverse-optic (TO) and longitudinal-optic (LO) phonons shifted to a lower frequency upon changing the observed crystal plane from polar to semi-polar to nonpolar. This result is well explained by the mixing of A1 and E1 optical phonons. In addition, we analyzed in detail the frequency of LO-phonon-plasmon-coupled (LOPC) modes by calculating the peak frequency as a function of carrier concentration and the propagation direction of the LOPC mode. Carrier densities deduced by the analysis showed excellent agreement with the results of Hall measurements. We provide a simple, quick, and nondestructive procedure for identifying nonpolar GaN planes as well as obtaining the carrier concentration.
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78.30.Fs III-V and II-VI semiconductors
63.20.kk Phonon interactions with other quasiparticles
72.80.Ey III-V and II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
64.75.Ef Mixing

Structure and chemistry of the Si(111)/AlN interface

G. Radtke, M. Couillard, G. A. Botton, D. Zhu, and C. J. Humphreys

Appl. Phys. Lett. 100, 011910 (2012); http://dx.doi.org/10.1063/1.3674984 (3 pages) | Cited 5 times

Online Publication Date: 5 January 2012

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We investigate the atomic structure and the chemistry of the Si(111)/AlN interface for an AlN film grown at low-temperature (735 °C) by metalorganic vapor phase epitaxy. A heterogeneous interface is formed from the alternation of crystallographically abrupt and partly amorphous regions. The polarity of the AlN film, along with the projected atomic structure of the crystalline interface, is retrieved using high-angle annular dark field imaging, and a model, based on these experimental observations, is proposed for the bonding at the interface. Electron energy-loss spectrum-imaging, however, also reveals a chemical intermixing, placing our growth conditions at the onset of SiNx interlayer formation.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors
79.20.Uv Electron energy loss spectroscopy
68.35.Ct Interface structure and roughness

Atomic-level study of twin nucleation from face-centered-cubic/body-centered-cubic interfaces in nanolamellar composites

W. Z. Han, J. S. Carpenter, J. Wang, I. J. Beyerlein, and N. A. Mara

Appl. Phys. Lett. 100, 011911 (2012); http://dx.doi.org/10.1063/1.3675447 (4 pages) | Cited 19 times

Online Publication Date: 6 January 2012

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We report deformation twinning in Cu within accumulative roll-bonded Cu-Nb nanolamellar composites. Twins appear connected to the Nb{112}//Cu{112} interface with the Kurdjumov-Sachs orientation relationship, which we show to be ordered and faceted. The interface adopts a different faceted structure after twinning. Our analysis suggests that deformation twinning involves facet dissociation and slip-transfer from the Nb layer to the Cu layer due to a geometrically favorable slip transmission pathway.
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61.72.Mm Grain and twin boundaries
64.60.qj Studies of nucleation in specific substances
68.55.A- Nucleation and growth
81.07.-b Nanoscale materials and structures: fabrication and characterization
68.65.Ac Multilayers

Optical properties of cobalt slanted columnar thin films passivated by atomic layer deposition

Daniel Schmidt, Eva Schubert, and Mathias Schubert

Appl. Phys. Lett. 100, 011912 (2012); http://dx.doi.org/10.1063/1.3675549 (4 pages) | Cited 3 times

Online Publication Date: 6 January 2012

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Optical properties of passivated metal slanted columnar thin films from cobalt within the visible spectral region are reported. Glancing angle deposition is utilized to grow slanted nanocolumns which have been conformally coated with Al2O3 by a subsequent atomic layer deposition process. A generalized anisotropic Bruggeman effective medium approximation has been employed to analyze spectroscopic generalized ellipsometry data. The modified homogenization approach allows for determination of biaxial (monoclinic) optical and structural properties as well as fractions of three film constituents. The conformal alumina passivation layer preserves the pristine metal character of the nanostructures and prevents oxidation and aging effects.
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78.66.Nk Insulators
78.40.Ha Other nonmetallic inorganics
81.65.Rv Passivation
61.46.-w Structure of nanoscale materials
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Low activation energy for the removal of excess nitrogen in nitrogen rich indium nitride

Kenneth S. A. Butcher, Patrick P.-T. Chen, and James E. Downes

Appl. Phys. Lett. 100, 011913 (2012); http://dx.doi.org/10.1063/1.3673839 (3 pages) | Cited 1 time

Online Publication Date: 6 January 2012

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For some InN films large amounts of excess nitrogen are seen at low growth temperatures. Recent studies have revised downward the defect formation energies for several forms of nitrogen rich point-defects in InN. Here we calculate an activation energy of 0.4 ± 0.1 eV for the thermally activated removal of much of the excess nitrogen, believed to be interstitial nitrogen. This low energy barrier is shown to support the case for a low defect formation energy of the same native defect, although it is pointed out that non-equilibrium plasma based conditions are required to reach these lower defect formation energies.
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61.72.jj Interstitials
68.55.ag Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
52.77.-j Plasma applications
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