APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

7 May 2012

Volume 100, Issue 19, Articles (19xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 191901 (2012); http://dx.doi.org/10.1063/1.4709436 (4 pages)

Muamer Kadic, Tiemo Bückmann, Nicolas Stenger, Michael Thiel, and Martin Wegener
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

On the practicability of pentamode mechanical metamaterials

Muamer Kadic, Tiemo Bückmann, Nicolas Stenger, Michael Thiel, and Martin Wegener

Appl. Phys. Lett. 100, 191901 (2012); http://dx.doi.org/10.1063/1.4709436 (4 pages) | Cited 6 times

Online Publication Date: 7 May 2012

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
Conceptually, all conceivable three-dimensional mechanical materials can be built from pentamode materials. Pentamodes also enable to implement three-dimensional transformation elastodynamics—the analogue of transformation optics. However, pentamodes have not been realized experimentally. Here, we investigate inasmuch the pentamode theoretical ideal suggested by Milton and Cherkaev in 1995 can be approximated by a metamaterial with current state-of-the-art lithography. Using numerical calculations calibrated by our fabricated three-dimensional microstructures, we find that the figure of merit, i.e., the ratio of bulk modulus to shear modulus, can realistically be made as large as about 1000.
Show PACS
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli

Rate dependence of the serrated flow in Ni-10Pd during high temperature instrumented microindentation

Bin Gan and Sammy Tin

Appl. Phys. Lett. 100, 191902 (2012); http://dx.doi.org/10.1063/1.4712130 (4 pages) | Cited 1 time

Online Publication Date: 7 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Instrumented indentation tests were conducted on a pure nickel and a Ni-10Pd solid solution at 450 °C with loading rates varying from 62.5 to 1000 mN/s. The load–depth curves from the pure nickel exhibited a smooth and continuous transition; while the load–depth curves from the Ni-10Pd were initially smooth and then became serrated after reaching a critical load. Increases in loading rates resulted in an earlier occurrence of the serrated flow with a higher load threshold. The mechanism responsible for the serration was delineated by accounting for the reconfiguration of dislocation substructures and the interactions between solutes and forest dislocations.
Show PACS
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
62.20.F- Deformation and plasticity
61.72.Lk Linear defects: dislocations, disclinations
62.20.Qp Friction, tribology, and hardness

Generation of acoustic pulses from a photo-acoustic transducer measured by time-resolved x-ray diffraction

Yuan Gao and Matthew F. DeCamp

Appl. Phys. Lett. 100, 191903 (2012); http://dx.doi.org/10.1063/1.4711045 (4 pages)

Online Publication Date: 7 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Picosecond acoustic pulses generated by ultrafast optical excitation of a 100 nm gold photo-acoustic transducer deposited on a germanium substrate are observed using time-resolved x-ray diffraction. The resulting pump-probe spectra reveal that the spatiotemporal structure of the acoustic pulse is bipolar with acoustic wavevectors up to inverse of the film thickness.
Show PACS
43.38.-p Transduction; acoustical devices for the generation and reproduction of sound
78.47.D- Time resolved spectroscopy (>1 psec)
78.20.Pa Photoacoustic effects
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Method to determine hkl strains and shear moduli under torsion using neutron diffraction

R. Woracek, J. R. Bunn, D. Penumadu, and C. R. Hubbard

Appl. Phys. Lett. 100, 191904 (2012); http://dx.doi.org/10.1063/1.4712043 (5 pages) | Cited 1 time

Online Publication Date: 8 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An experimental method, using in-situ neutron diffraction for the measurement of shear strain, based on (hkl) lattice spacing changes under torsional loading, is described. This method provides the ability to probe the response of crystallographic planes to application of shear stress, inside the bulk of samples that are subjected to torsion. To demonstrate the method, shear moduli corresponding to bcc (211), (200), and (110) were experimentally determined for a solid cylinder of ferritic alloy 12L14 under elastic loading. Results indicate that the elastic constants determined under torsional shear show a different degree of anisotropy than those obtained from tensile loading.
Show PACS
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.de Elastic moduli
62.20.F- Deformation and plasticity

Real-time x-ray diffraction of metastable phases during solidification from the undercooled LuFeO3 melt by two-dimensional detector at 1 kHz

Malahalli Vijaya Kumar, K. Kuribayashi, K. Nagashio, T. Ishikawa, J. Okada, J. Yu, S. Yoda, and Y. Katayama

Appl. Phys. Lett. 100, 191905 (2012); http://dx.doi.org/10.1063/1.4712124 (4 pages)

Online Publication Date: 8 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In-situ identification of metastable phases formed from the undercooled LuFeO3 melt under controlled oxygen partial pressure Po2 was studied by x-ray diffraction measurements at a synchrotron radiation source. Real-time observation of the formation and growth of individual phases during the single recalescence of Lu3Fe2O7 and LuFe2O4 phases at Po2 of 1 × 103 Pa has been revealed by a high speed imaging system at 1 kHz. The obtained diffraction pattern of the metastable phase in the LuFeO3 system was consistent with that of the metastable and stable phases reported in the Lu-Fe-O system.
Show PACS
81.30.Fb Solidification

Optical phonon lifetimes in sputtered AlN thin films

P. Pobedinskas, B. Ruttens, J. D’Haen, and K. Haenen

Appl. Phys. Lett. 100, 191906 (2012); http://dx.doi.org/10.1063/1.4711773 (4 pages) | Cited 1 time

Online Publication Date: 8 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We study the vibrational properties of AlN thin films deposited on silicon (100) substrates by the reactive DC-pulsed magnetron sputtering. The frequencies and lifetimes of the E1(TO) and A1(LO) optical phonons are calculated from Fourier transform infrared spectra using the factorized model of a damped oscillator. We analyze the structural properties by the x-ray diffraction technique to correlate the elongation of phonon lifetimes with increasing film thickness. The lifetimes of the phonon modes in AlN thin films are compared to the values in a single crystal.
Show PACS
63.22.Dc Free films
68.55.ag Semiconductors
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
81.15.Cd Deposition by sputtering

Oxygen transport and GeO2 stability during thermal oxidation of Ge

S. R. M. da Silva, G. K. Rolim, G. V. Soares, I. J. R. Baumvol, C. Krug, L. Miotti, F. L. Freire, Jr., M. E. H. M. da Costa, and C. Radtke

Appl. Phys. Lett. 100, 191907 (2012); http://dx.doi.org/10.1063/1.4712619 (4 pages)

Online Publication Date: 9 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Oxygen transport during thermal oxidation of Ge and desorption of the formed Ge oxide are investigated. Higher oxidation temperatures and lower oxygen pressures promote GeO desorption. An appreciable fraction of oxidized Ge desorbs during the growth of a GeO2 layer. The interplay between oxygen desorption and incorporation results in the exchange of O originally present in GeO2 by O from the gas phase throughout the oxide layer. This process is mediated by O vacancies generated at the GeO2/Ge interface. The formation of a substoichiometric oxide is shown to have direct relation with the GeO desorption.
Show PACS
81.65.Mq Oxidation
68.43.Nr Desorption kinetics

Broadband transmission enhancement of acoustic waves through a hybrid grating

Chunyin Qiu, Rui Hao, Feng Li, Shengjun Xu, and Zhengyou Liu

Appl. Phys. Lett. 100, 191908 (2012); http://dx.doi.org/10.1063/1.4714719 (4 pages) | Cited 1 time

Online Publication Date: 9 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report an anomalous transmission enhancement of acoustic waves through a hybrid grating. The fundamental physics behind this phenomenon can be captured well by the improved impedance matching between the hybrid grating and the background fluid. This type of acoustic transparency is broadband and can be robust against the incident angle, which is drastically different from the previously reported mechanisms that are closely related with resonances. Potential applications of this effect can be anticipated in ultrasonic devices.
Show PACS
43.20.-f General linear acoustics

Nanoscale quantification of octahedral tilts in perovskite films

Jinwoo Hwang, Jack Y. Zhang, Junwoo Son, and Susanne Stemmer

Appl. Phys. Lett. 100, 191909 (2012); http://dx.doi.org/10.1063/1.4714734 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
NiO6-octahedral tilts in ultrathin LaNiO3 films were studied using position averaged convergent beam electron diffraction (PACBED) in scanning transmission electron microscopy. Both the type and magnitude of the octahedral tilts were determined by comparing PACBED experiments to frozen phonon multislice simulations. It is shown that the out-of-plane octahedral tilt of an epitaxial film under biaxial tensile stress (0.78% in-plane tensile strain) increases by ∼20%, while the in-plane rotation decreases by ∼80%, compared to the unstrained bulk material.
Show PACS
68.55.-a Thin film structure and morphology
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Mechanisms of fragmentation of aluminum-tungsten granular composites under dynamic loading

K. L. Olney, V. F. Nesterenko, and D. J. Benson

Appl. Phys. Lett. 100, 191910 (2012); http://dx.doi.org/10.1063/1.4711768 (4 pages)

Online Publication Date: 9 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Numerical simulations of aluminum (Al) and tungsten (W) granular composite rings under various dynamic loading conditions due to explosive loading were performed. Three competing mechanisms of fragmentation were observed: a continuum level mechanism generating macrocracks with a size scale comparable to the case width, a mesoscale mechanism generating voids and microcracks at the unbonded Al/W interfaces due to tensile strains, and mesoscale jetting due to the development of large velocity gradients between the W particles and surrounding Al. These mesoscale mechanisms can be used to tailor the size of the fragments (macro to mesoscale) by selecting an appropriate initial mesostructure for a given loading condition.
Show PACS
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mt Cracks
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Sequential three-step three-photon near-infrared quantum splitting in β-NaYF4:Tm3+

D. C. Yu, S. Ye, M. Y. Peng, Q. Y. Zhang, and L. Wondraczek

Appl. Phys. Lett. 100, 191911 (2012); http://dx.doi.org/10.1063/1.4714505 (4 pages) | Cited 4 times

Online Publication Date: 10 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on sequential three-step three-photon near-infrared (NIR) quantum splitting in Tm3+-doped β-NaYF4, where an incident blue photon around 470 nm is split into three NIR photons (1165, 1466, and 1800 nm). The underlying mechanism is analyzed by means of static and dynamic photoemission spectroscopy. Here, an experimental total quantum yield of ∼32% is obtained. When quenching due to residual hydroxyl groups and other defect species can be overcome, numerical analyses indicate a theoretical maximum quantum yield of 158%, suggesting application in efficient spectral converters.
Show PACS
78.55.Hx Other solid inorganic materials
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.40.Gh Other heat and thermomechanical treatments

Nanocrystalline-to-amorphous transition in nanolaminates grown by low temperature atomic layer deposition and related mechanical properties

R. Raghavan, M. Bechelany, M. Parlinska, D. Frey, W. M. Mook, A. Beyer, J. Michler, and I. Utke

Appl. Phys. Lett. 100, 191912 (2012); http://dx.doi.org/10.1063/1.4711767 (4 pages) | Cited 2 times

Online Publication Date: 10 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on a comprehensive structural and nanoindentation study of nanolaminates of Al2O3 and ZnO synthesized by atomic layer deposition (ALD). By reducing the bilayer thickness from 50 nm to below 1 nm, the nanocrystal size could be controlled in the nanolaminate structure. The softer and more compliant response of the multilayers as compared to the single layers of Al2O3 and ZnO is attributed to the structural change from nanocrystalline to amorphous at smaller bilayer thicknesses. It is also shown that ALD is a unique technique for studying the inverse Hall-Petch softening mechanism (E. Voce and D. Tabor, J. Inst. Metals 79(12), 465 (1951)) related to grain size effects in nanomaterials.
Show PACS
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
64.70.K- Solid-solid transitions
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Stretch-induced softening of bending rigidity in graphene

Xinghua Shi, Bo Peng, Nicola M. Pugno, and Huajian Gao

Appl. Phys. Lett. 100, 191913 (2012); http://dx.doi.org/10.1063/1.4716024 (5 pages) | Cited 2 times

Online Publication Date: 10 May 2012

Full Text: Read Online (HTML) | Download PDF


See Also: Publisher's Note

Show Abstract
First principle calculations are performed to show that the bending rigidity of graphene can be softened considerably with in-plane stretching. This phenomenon can be attributed to stretch-induced loosening of atomic packing and should be of fundamental significance for graphene-based structures and devices.
Show PACS
81.40.Lm Deformation, plasticity, and creep
62.20.de Elastic moduli
62.20.F- Deformation and plasticity
61.48.Gh Structure of graphene
81.05.ue Graphene
81.40.Jj Elasticity and anelasticity, stress-strain relations

On the origin of the 265 nm absorption band in AlN bulk crystals

Ramón Collazo, Jinqiao Xie, Benjamin E. Gaddy, Zachary Bryan, Ronny Kirste, Marc Hoffmann, Rafael Dalmau, Baxter Moody, Yoshinao Kumagai, Toru Nagashima, Yuki Kubota, Toru Kinoshita, Akinori Koukitu, Douglas L. Irving, and Zlatko Sitar

Appl. Phys. Lett. 100, 191914 (2012); http://dx.doi.org/10.1063/1.4717623 (5 pages) | Cited 3 times

Online Publication Date: 10 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Single crystal AlN provides a native substrate for Al-rich AlGaN that is needed for the development of efficient deep ultraviolet light emitting and laser diodes. An absorption band centered around 4.7 eV (∼265 nm) with an absorption coefficient above 1000 cm−1 is observed in these substrates. Based on density functional theory calculations, substitutional carbon on the nitrogen site introduces absorption at this energy. A series of single crystalline wafers were used to demonstrate that this absorption band linearly increased with carbon, strongly supporting the model that CN- is the predominant state for carbon in AlN.
Show PACS
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors

Sub-0.1 nm-resolution quantitative scanning transmission electron microscopy without adjustable parameters

C. Dwyer, C. Maunders, C. L. Zheng, M. Weyland, P. C. Tiemeijer, and J. Etheridge

Appl. Phys. Lett. 100, 191915 (2012); http://dx.doi.org/10.1063/1.4711766 (4 pages) | Cited 5 times

Online Publication Date: 11 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Atomic-resolution imaging in the scanning transmission electron microscope (STEM) constitutes a powerful tool for nanostructure characterization. Here, we demonstrate the quantitative interpretation of atomic-resolution high-angle annular dark-field (ADF) STEM images using an approach that does not rely on adjustable parameters. We measure independently the instrumental parameters that affect sub-0.1 nm-resolution ADF images, quantify their individual and collective contributions to the image intensity, and show that knowledge of these parameters enables a quantitative interpretation of the absolute intensity and contrast across all accessible spatial frequencies. The analysis also provides a method for the in-situ measurement of the STEM’s effective source distribution.
Show PACS
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close