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25 Jan 2010

Volume 96, Issue 4, Articles (04xxxx)

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Appl. Phys. Lett. 96, 042501 (2010); http://dx.doi.org/10.1063/1.3291942 (3 pages)

Daniel Stickler, Robert Frömter, Holger Stillrich, Christian Menk, Carsten Tieg, Simone Streit-Nierobisch, Michael Sprung, Christian Gutt, Lorenz-M. Stadler, Olaf Leupold, Gerhard Grübel, and Hans Peter Oepen
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Thermoreflectance dependence on Fermi surface electron number density perturbations

Patrick E. Hopkins

Appl. Phys. Lett. 96, 041901 (2010); http://dx.doi.org/10.1063/1.3292212 (3 pages) | Cited 1 time

Online Publication Date: 25 January 2010

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The effects of an optical excitation on the thermoreflectance spectra of a solid are studied. A photonic excitation with sufficient energy will cause a perturbation in the electron number density around the Fermi surface. As the number density changes, so do the plasma frequency and carrier scattering rates, creating a change in the thermoreflectance response. Not accounting for the appropriate electron number density around the Fermi level after an optical excitation leads to an underestimate of electron scattering rates.
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78.20.N- Thermo-optic effects
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
73.20.At Surface states, band structure, electron density of states
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Defects analysis at the nanometric scale in Ca3Co4O9 thin films

R. Moubah, S. Colis, C. Ulhaq-Bouillet, and A. Dinia

Appl. Phys. Lett. 96, 041902 (2010); http://dx.doi.org/10.1063/1.3292590 (3 pages) | Cited 4 times

Online Publication Date: 25 January 2010

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We report on the nature and origin of structural defects at a nanometric scale in incommensurate Ca3Co4O9 thin films deposited by pulsed laser ablation on Al2O3(001) substrates. X-ray diffraction suggests that the deposited films have a well defined texture and that are free of spurious phases. However, cross section scanning high resolution transmission electron microscopy observations show the presence of regions with different kinds of stacking. Such regions present different chemical compositions from that of Ca3Co4O9 and are not detectable in diffraction mode. The local chemical analysis and the interplane distance measurement suggest that these defects correspond to the formation of the CaCo2O4 spurious phase. This phase has a similar structure and close lattice parameters with those of Ca3Co4O9. The origin of the formation of CaCo2O4 is discussed in terms of (i) strains due to the substrate which tend to suppress the incommensurability of the system, and (ii) local chemical nonstoichiometry.
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68.55.-a Thin film structure and morphology
61.46.-w Structure of nanoscale materials
64.70.K- Solid-solid transitions
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Mk Laser-assisted deposition
81.15.Fg Pulsed laser ablation deposition
61.66.Bi Elemental solids
61.66.Dk Alloys

Influence of carbon content on the lattice variation, magnetic and electronic transport properties in Mn3SnCx

Yongchun Wen, Cong Wang, Man Nie, Ying Sun, Lihua Chu, and Cheng Dong

Appl. Phys. Lett. 96, 041903 (2010); http://dx.doi.org/10.1063/1.3295695 (3 pages) | Cited 10 times

Online Publication Date: 26 January 2010

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The structural, magnetic, lattice, and electronic transport properties of Mn3SnCx compounds were investigated. Variation in carbon content from 0.6 to 1.2 does not change the crystal structure. With the increasing of x, the magnetic order changes from antiferromagnetic to ferromagnetic, and the transition temperature increases. The lattice constant shrinks around magnetic transition temperature when temperature increases. The total behavior of Mn3SnCx in temperature dependence of resistivity is very complex. For some Mn3SnCx, the temperature coefficient of resistivity is negative in the scope of magnetic order temperature. For other Mn3SnCx, the total behavior is metallic-type, and the resistivity appears an abrupt change.
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61.66.-f Structure of specific crystalline solids
61.50.-f Structure of bulk crystals
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Mechanically tunable surface plasmon resonance based on gold nanoparticles and elastic membrane polydimethylsiloxane composite

Yu-Lun Chiang, Chih-Wei Chen, Chun-Hsiung Wang, Chun-Yi Hsieh, Yung-Ting Chen, Han-Yu Shih, and Yang-Fang Chen

Appl. Phys. Lett. 96, 041904 (2010); http://dx.doi.org/10.1063/1.3295702 (3 pages) | Cited 11 times

Online Publication Date: 26 January 2010

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Surface plasmon in nanoscaled materials has recently attracted a great deal of attention due to its possibility in a wide range of application. From a practical standpoint, it is desirable for the devices having a tunability of surface plasmon frequency. To achieve this goal, in this study, a composite consisting of two-dimensional gold nanoparticles array embedded in elastic polydimethylsiloxane (PDMS) membrane has been synthesized. Because the elastic PDMS membrane has a high malleability, with an external stress, it is very easy to regulate the interparticle distance in the gold nanoparticle array. The change in the distance between each nanoparticle will alter the surface plasmon interaction, and hence surface plasmon frequency can be manipulated. It is found that when the interparticle distance increases, the enhanced surface plasma mutual coupling will cause the blueshift of surface plasmon resonance frequency. The observed result satisfies the forecast based on electromagnetic theory.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.67.Hc Quantum dots
78.66.Sq Composite materials
78.40.Kc Metals, semimetals, and alloys

Elastic-strain distribution in metallic film-polymer substrate composites

G. Geandier, P.-O. Renault, E. Le Bourhis, Ph. Goudeau, D. Faurie, C. Le Bourlot, Ph. Djémia, O. Castelnau, and S. M. Chérif

Appl. Phys. Lett. 96, 041905 (2010); http://dx.doi.org/10.1063/1.3293450 (3 pages) | Cited 13 times

Online Publication Date: 26 January 2010

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Synchrotron x-ray radiation was used for in situ strain measurements during uniaxial tests on polymer substrates coated by a metallic gold film 400 nm thick deposited without interlayer or surface treatment. X-ray diffraction allowed capturing both components elastic strains and determining how these were partitioned between the metallic film and the polymeric substrate. For strains below 0.8%, deformation is continuous through the metal-polymer interface while above, the onset of plasticity in the metallic film induces a shift between film and substrate elastic strains.
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68.35.Gy Mechanical properties; surface strains
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity

Acoustic metamaterial panels for sound attenuation in the 50–1000 Hz regime

Z. Yang, H. M. Dai, N. H. Chan, G. C. Ma, and Ping Sheng

Appl. Phys. Lett. 96, 041906 (2010); http://dx.doi.org/10.1063/1.3299007 (3 pages) | Cited 27 times

Online Publication Date: 26 January 2010

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We show experimentally that thin membrane-type acoustic metamaterials can serve as a total reflection nodal surface at certain frequencies. The small decay length of the evanescent waves at these frequencies implies that several membrane panels can be stacked to achieve broad-frequency effectiveness. We report the realization of acoustic metamaterial panels with thickness ≤ 15 mm and weight ≤ 3 kg/m2 demonstrating 19.5 dB of internal sound transmission loss (STL) at around 200 Hz, and stacked panels with thickness ≤ 60 mm and weight ≤ 15 kg/m2 demonstrating an average STL of >40 dB over a broad range from 50 to 1000 Hz.
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81.05.Xj Metamaterials for chiral, bianisotropic and other complex media
62.65.+k Acoustical properties of solids
43.20.Hq Velocity and attenuation of acoustic waves

Room temperature study of the optical switching of a spin crossover compound inside its thermal hysteresis loop

G. Gallé, D. Deldicque, J. Degert, Th. Forestier, J.-F. Létard, and E. Freysz

Appl. Phys. Lett. 96, 041907 (2010); http://dx.doi.org/10.1063/1.3294312 (3 pages) | Cited 7 times

Online Publication Date: 27 January 2010

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We have studied the low-spin to high spin state phase transition induced by a single or a sequence of nanosecond laser pulses within the thermal hysteresis loop of the [Fe(NH2-trz)3](NO3)2-H2O spin crossover compound. We demonstrate that the final state that is photoinduced can be finely controlled by changing the central wavelength and the energy of the laser pulses. A simple model accounts for the observed phenomena and paves the way for the practical applications to optical data storage at room temperature of spin state transition compounds.
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42.70.Mp Nonlinear optical crystals
42.79.Vb Optical storage systems, optical disks
42.65.Pc Optical bistability, multistability, and switching, including local field effects
78.20.N- Thermo-optic effects
42.70.Gi Light-sensitive materials

The electrostatic coupling of longitudinal optical phonon and plasmon in wurtzite InN thin films

Y.-M. Chang, S. C. Liou, C. H. Chen, H.-M. Lee, and S. Gwo

Appl. Phys. Lett. 96, 041908 (2010); http://dx.doi.org/10.1063/1.3299021 (3 pages) | Cited 1 time

Online Publication Date: 27 January 2010

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We utilize coherent longitudinal optical phonon as an optical nanoprobe to investigate the plasmonic behavior of wurtzite c-plane InN thin films. The transition from the three-dimensional electron gas in InN bulk toward the two-dimensional electron gas in InN thin film is revealed via measuring the coupling strength of coherent A1(LO) phonon and plasmon coupling mode. The coupling strength diminishes as the film thickness reduces and finally vanishes at 3±1 nm. This phenomenon is ascribed to the detuning of the intersubband plasmon frequency above the A1(LO) frequency, which is originated from the electronic quantum confinement in InN thin films.
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63.22.Dc Free films
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
63.20.kk Phonon interactions with other quasiparticles
68.55.jd Thickness
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Control of direct band gap emission of bulk germanium by mechanical tensile strain

M. El Kurdi, H. Bertin, E. Martincic, M. de Kersauson, G. Fishman, S. Sauvage, A. Bosseboeuf, and P. Boucaud

Appl. Phys. Lett. 96, 041909 (2010); http://dx.doi.org/10.1063/1.3297883 (3 pages) | Cited 20 times

Online Publication Date: 28 January 2010

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We show that the recombination energy of the direct band gap photoluminescence (PL) of germanium can be controlled by an external mechanical stress. The stress is provided by an apparatus commonly used for bulge or blister test. An energy redshift up to 60 meV is demonstrated for the room temperature PL of a thin germanium membrane (125 nm wavelength shift from 1535 to 1660 nm). This PL shift is correlated with the in-plane tensile strain generated in the film. A biaxial tensile strain larger than 0.6% is achieved by this method. This mechanical strain allows to approach the direct band gap condition for germanium which is of tremendous importance to achieve lasing with this material.
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78.55.Ap Elemental semiconductors
71.20.Mq Elemental semiconductors

Double electrical percolation phenomenon during the crystallization of an amorphous Ge2Sb2Te5 thin film under continuous heating

Yunjung Choi and Young-Kook Lee

Appl. Phys. Lett. 96, 041910 (2010); http://dx.doi.org/10.1063/1.3298357 (3 pages) | Cited 3 times

Online Publication Date: 28 January 2010

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Crystallization behaviors of an amorphous Ge2Sb2Te5 thin film were investigated by in situ measurements of electrical resistivity Rel and optical reflectivity Rop and by transmission electron microscopy during isothermal annealing and continuous heating. Rop increased first and then Rel decreased during the initial stage of crystallization for both annealing conditions due to the electrical percolation of heterogeneous crystallization at the film surface. The two-step decrease in Rel during continuous heating, unlike the monotonous decrease in Rel during isothermal annealing, was induced by the percolation phenomenon via homogeneous crystallization inside the film. The effective activation energy for homogeneous crystallization was 4.30 eV.
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64.60.ah Percolation
81.40.Gh Other heat and thermomechanical treatments
73.61.Jc Amorphous semiconductors; glasses
64.70.dg Crystallization of specific substances

Time resolved photoluminescence of In(N)As quantum dots embedded in GaIn(N)As/GaAs quantum well

M. Syperek, R. Kudrawiec, M. Baranowski, G. Sȩk, J. Misiewicz, D. Bisping, B. Marquardt, A. Forchel, and M. Fischer

Appl. Phys. Lett. 96, 041911 (2010); http://dx.doi.org/10.1063/1.3299258 (3 pages) | Cited 3 times

Online Publication Date: 29 January 2010

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Carrier dynamics in In(N)As quantum dots embedded in GaIn(N)As quantum well has been studied by time resolved photoluminescence. We have shown that incorporation of nitrogen into InAs/InGaAs system caused a redshift of the ground state emission due to the change in the energy gap and strain distribution, and simultaneously changed the size and density of dots. This has differently affected the dynamic properties at low and room temperature. Small amount of nitrogen in the InAs/InGaAs quantum dot system has appeared to enhance the quantum confinement allowing to reach 1.3 μm emission and has not deteriorated the optical material quality.
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78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
73.21.La Quantum dots

Influence of random roughness on cantilever curvature sensitivity

O. Ergincan, G. Palasantzas, and B. J. Kooi

Appl. Phys. Lett. 96, 041912 (2010); http://dx.doi.org/10.1063/1.3299713 (3 pages) | Cited 6 times

Online Publication Date: 29 January 2010

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In this work we explore the influence of random surface roughness on the cantilever sensitivity to respond to curvature changes induced by changes in surface stress. The roughness is characterized by the out-of-plane roughness amplitude w, the lateral correlation length ξ, and the roughness or Hurst exponent H(0<H<1). The cantilever sensitivity is found to decrease with increasing roughness (decreasing H and/or increasing ratio w/ξ) or equivalently increasing local surface slope. Finally, analytic expressions of the cantilever sensitivity as a function of the parameters w, ξ, and H are derived in order to allow direct implementation in sensing systems.
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68.35.Ct Interface structure and roughness
68.35.Gy Mechanical properties; surface strains
07.10.Cm Micromechanical devices and systems

Anisotropy of tensile stresses and cracking in nonbasal plane AlxGa1−xN/GaN heterostructures

Erin C. Young, Alexey E. Romanov, Chad S. Gallinat, Asako Hirai, Glenn E. Beltz, and James S. Speck

Appl. Phys. Lett. 96, 041913 (2010); http://dx.doi.org/10.1063/1.3276561 (3 pages) | Cited 5 times

Online Publication Date: 29 January 2010

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AlxGa1−xN films grown on nonpolar m {1math00} and {11math2} semipolar orientations of freestanding GaN substrates were investigated over a range of stress states (x ≤ 0.17). Cracking on the (0001) plane was observed beyond a critical thickness in the {1math00} oriented films, while no cracking was observed for {11math2} films. Theoretical analysis of tensile stresses in AlxGa1−xN for the relevant planes revealed that anisotropy of in-plane biaxial stress for the nonpolar {1math00} planes results in the highest normal stresses on the c-planes, consistent with experimental observations. Shear stresses are significant in the semipolar case, suggesting that misfit dislocation formation provides an alternative mechanism for stress relief.
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68.60.Bs Mechanical and acoustical properties
68.37.Ps Atomic force microscopy (AFM)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.jd Thickness
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.55.ag Semiconductors

Investigation of Jahn–Teller splitting with O 1s x-ray absorption spectroscopy in strained Nd1−xCaxMnO3 thin films

Daniel Hsu, Y. S. Chen, M. Y. Song, C. H. Chuang, Minn-Tsong Lin, W. F. Wu, and J. G. Lin

Appl. Phys. Lett. 96, 041914 (2010); http://dx.doi.org/10.1063/1.3299023 (3 pages)

Online Publication Date: 29 January 2010

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Electronic structures of strained Nd1−xCaxMnO3 (NCMO) thin films with x = 0 to 0.8 are investigated via x-ray absorption spectroscopy (XAS). The obtained O 1s spectra within the photon energy 529–535 eV can be decomposed into eg↑1, eg↑2, t2g↓, and eg↓ bands. Based on the assigned energy levels of these band states, the energies of magnetic exchange, crystal field and Jahn–Teller (JT) splitting are determined. Particularly, the JT splitting is around 0.8 eV, which is observed with O 1s XAS for the first time in NCMO thin films.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.70.Ch Crystal and ligand fields
78.70.Dm X-ray absorption spectra
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