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15 Mar 2010

Volume 96, Issue 11, Articles (11xxxx)

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Appl. Phys. Lett. 96, 111901 (2010); http://dx.doi.org/10.1063/1.3358107 (3 pages)

B. Rožič, S. Krause, H. Finkelmann, G. Cordoyiannis, and Z. Kutnjak
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Controlling the thermomechanical response of liquid-crystalline elastomers by influencing their critical behavior

B. Rožič, S. Krause, H. Finkelmann, G. Cordoyiannis, and Z. Kutnjak

Appl. Phys. Lett. 96, 111901 (2010); http://dx.doi.org/10.1063/1.3358107 (3 pages) | Cited 2 times

Online Publication Date: 15 March 2010

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The profound understanding of the mechanisms that affect the thermomechanical response of liquid-crystalline elastomers is of significant importance for applications. In the vicinity of a phase transition this response is reflected to the thermodynamic critical behavior. We demonstrate that two main-chain liquid-crystalline elastomers of identical composition, crosslinked in temperatures corresponding to different thermodynamic phases, exhibit dramatically different thermal behavior as derived from high-resolution calorimetry. Hence, a previously unexplored parameter for controlling the elastomers critical behavior is revealed, exhibiting a very strong effect. Moreover, the relative strength of various discovered mechanisms that control the critical behavior is discussed.
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64.70.mj Experimental studies of liquid crystal transitions
81.40.Gh Other heat and thermomechanical treatments
61.30.Vx Polymer liquid crystals
65.20.Jk Studies of thermodynamic properties of specific liquids

Switchable phononic wave filtering, guiding, harvesting, and actuating in polarization-patterned piezoelectric solids

Cory J. Rupp, Martin L. Dunn, and Kurt Maute

Appl. Phys. Lett. 96, 111902 (2010); http://dx.doi.org/10.1063/1.3341197 (3 pages) | Cited 4 times

Online Publication Date: 15 March 2010

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We demonstrate the ability to manipulate the propagation of phononic (elastic, acoustic) waves in two-dimensional piezoelectric solids by spatially patterning the polarization distribution. We simulate the wave fields by the finite element method and demonstrate the ability to dynamically alter the wave propagation by switching (on/off) the piezoelectric behavior by operating the electrodes in a closed or open circuit configuration. The piezoelectric polarization patterns are nonintuitive and are determined by topology optimization. We illustrate the interesting response of optimally patterned phononic devices with four examples: a filter, a waveguide, an energy harvester, and a wave actuator.
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62.65.+k Acoustical properties of solids
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.65.-j Piezoelectricity and electromechanical effects
02.70.Dh Finite-element and Galerkin methods

High quality Ge epitaxial layers in narrow channels on Si (001) substrates

G. Wang, E. Rosseel, R. Loo, P. Favia, H. Bender, M. Caymax, M. M. Heyns, and W. Vandervorst

Appl. Phys. Lett. 96, 111903 (2010); http://dx.doi.org/10.1063/1.3360231 (3 pages) | Cited 9 times

Online Publication Date: 16 March 2010

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We demonstrate the selective growth of high quality Ge epitaxial layers in channels as narrow as 10 nm on patterned Si (001) substrates by a combination of low temperature growth and selective recrystallization using Ge melt and regrowth during a millisecond laser anneal. Filling narrow trenches at high growth temperature as required for obtaining high quality layers was shown to be prohibited by Ge outdiffusion due to the high Ge chemical potential in such narrow channels. At low temperature, a hydride-terminated surface is maintained which counteracts the outdiffusion of the Ge adatoms and provides excellent trench filling. The resulting low crystalline quality can be restored by a selective Ge melt and epitaxial regrowth using a millisecond laser anneal.
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68.55.ag Semiconductors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
61.72.Cc Kinetics of defect formation and annealing
81.05.Cy Elemental semiconductors
81.16.-c Methods of micro- and nanofabrication and processing

Effect of surface bonding on semiconductor nanoribbon wiggling structure

Yu Zhang, Minrui Yu, Donald E. Savage, Max G. Lagally, Robert H. Blick, and Feng Liu

Appl. Phys. Lett. 96, 111904 (2010); http://dx.doi.org/10.1063/1.3353972 (3 pages) | Cited 2 times

Online Publication Date: 17 March 2010

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SiGe nanomembranes and nanowires provide one important class of stretchable electronic materials. We have investigated a very interesting wiggling phenomenon of SiGe nanoribbons bonded to Si substrate as experimentally observed in a Hall-bar structure. Based on continuum linear stability analysis, we establish a scaling rule between the wiggling period and surface bonding area, in relation to the ratio of strain energy over the interfacial bonding energy.
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61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
72.20.My Galvanomagnetic and other magnetotransport effects
81.16.Dn Self-assembly
68.35.Md Surface thermodynamics, surface energies

Study on the activation of styrene-based shape memory polymer by medium-infrared laser light

Jinsong Leng, Dawei Zhang, Yanju Liu, Kai Yu, and Xin Lan

Appl. Phys. Lett. 96, 111905 (2010); http://dx.doi.org/10.1063/1.3353970 (3 pages) | Cited 7 times

Online Publication Date: 18 March 2010

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This paper demonstrates the feasibility of shape memory polymer (SMP) activation by medium-infrared laser light. Medium-infrared light is transmitted by an optical fiber embedded in the SMP matrix, and the shape recovery process and temperature distribution are recorded by an infrared camera. Light-induced SMP exhibits potential applications in biomedicines and flexible displays.
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42.62.-b Laser applications
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Pv Polymers, organic compounds
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Energy-harvesting device with mechanical frequency-up conversion mechanism for increased power efficiency and wideband operation

Seok-Min Jung and Kwang-Seok Yun

Appl. Phys. Lett. 96, 111906 (2010); http://dx.doi.org/10.1063/1.3360219 (3 pages) | Cited 13 times

Online Publication Date: 19 March 2010

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In this paper, we propose an energy-harvesting device that uses snap-through buckling for mechanical frequency-up conversion. The proposed device consists of buckled slender bridges with a proof mass and cantilever beams attached on them. When subjected to a low-frequency vibration above the threshold acceleration value, the buckled bridges snap through between two equilibrium states, providing high acceleration to the attached piezoelectric cantilever beams and thus causing them to resonate at a high frequency. A maximum power of 131 μW was generated at an excitation frequency of 30 Hz and a peak acceleration of 30 m/s2 by using a proposed device.
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84.60.-h Direct energy conversion and storage

Confinement effects of CdSe nanocrystals intercalated into mesoporous silica

Shu-Fang Chen, Chuan-Pu Liu, Andrei A. Eliseev, Dmitry I. Petukhov, and Sandip Dhara

Appl. Phys. Lett. 96, 111907 (2010); http://dx.doi.org/10.1063/1.3340903 (3 pages) | Cited 1 time

Online Publication Date: 19 March 2010

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CdSe nanocrystals are intercalated into ordered hexagonal arrays of mesoporous silica. The nanocrystals are clearly confined in the channels and their size was estimated to be consistent with the pore size. Transmission electron microscopy suggests that CdSe nanocrystals have a spherical morphology and are stabilized from aggregation after intercalation. The shift of the longitudinal optical bands in the Raman spectra is caused by a combination of phonon confinement and strain effects from the compressed lattice of the intercalated CdSe nanocrystals and the experimental results agree well to the theoretical consideration.
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81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
61.43.Gt Powders, porous materials
68.55.J- Morphology of films
81.05.Dz II-VI semiconductors

Real-time atomic force microscopy imaging of photoinduced surface deformation in AsxSe100−x chalcogenide films

M. L. Trunov, P. M. Lytvyn, P. M. Nagy, and O. M. Dyachyns’ka

Appl. Phys. Lett. 96, 111908 (2010); http://dx.doi.org/10.1063/1.3360229 (3 pages) | Cited 10 times

Online Publication Date: 19 March 2010

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We present direct measurements of the kinetics of surface relief gratings (SRGs) formation in amorphous AsxSe100−x (20 ≤ xAs ≤ 50) thin films. SRGs are induced in different holographic schemes of recording using near-band-gap light and their growth is further facilitated by illumination with an interference pattern and observed in real time by in situ atomic force microscopy. It is found that the kinetics of SRG formation depends upon film composition and incident light polarization. The light-stimulated vectorial surface deformations are maximized for Se-rich glasses and increase even further by additional illumination during recording.
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42.79.Dj Gratings
68.35.bj Amorphous semiconductors, glasses
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
68.37.Ps Atomic force microscopy (AFM)
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