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27 Aug 2012

Volume 101, Issue 9, Articles (09xxxx)

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Appl. Phys. Lett. 101, 091102 (2012); http://dx.doi.org/10.1063/1.4747168 (3 pages)

Hagay Shpaisman, Bhaskar Jyoti Krishnatreya, and David G. Grier
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Excimer laser ablation of thick SiOx-films: Etch rate measurements and simulation of the ablation threshold

J. Ihlemann, J. Meinertz, and G. Danev

Appl. Phys. Lett. 101, 091901 (2012); http://dx.doi.org/10.1063/1.4748127 (4 pages)

Online Publication Date: 27 August 2012

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Excimer laser ablation of 4.5 μm thick SiOx-films with x ≈ 1 is investigated at 193 nm, 248 nm, and 308 nm. Strong absorption enables precisely tunable removal depths. The ablation rates correlate with laser penetration depths calculated from low level absorption coefficients. The experimental ablation thresholds are in agreement with numerical simulations on the basis of linear absorption and one-dimensional heat flow. This behaviour is similar to that of strongly UV-absorbing polymers, leading to well controllable micro machining prospects. After laser processing, SiOx can be converted to SiO2, opening a route to laser based fabrication of micro optical components.
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81.65.Cf Surface cleaning, etching, patterning
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
66.30.Xj Thermal diffusivity
42.55.Lt Gas lasers including excimer and metal-vapor lasers
79.20.Eb Laser ablation
02.60.Cb Numerical simulation; solution of equations

Bond lengths and lattice structure of InP0.52Sb0.48 grown on GaAs

Chen-Jun Wu, Zhe-Chuan Feng, Wen-Ming Chang, Chih-Chung Yang, and Hao-Hsiung Lin

Appl. Phys. Lett. 101, 091902 (2012); http://dx.doi.org/10.1063/1.4748295 (4 pages) | Cited 1 time

Online Publication Date: 27 August 2012

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We performed reciprocal space mapping (RSM) and extended x-ray absorption fine structure (EXAFS) measurements to investigate the lattice structure of InP0.52Sb0.48 grown on GaAs. The RSM data reveal the existence of residual strain in the 1-μm-thick epilayer. The average vertical to horizontal lattice constant ratio, az/axy, is 1.009. We used a valence force field model to calculate the distortion energy and bond lengths of InPSb supercells with different az/axy ratio. The calculated InP and InSb bond lengths are in good agreement with the results of EXAFS. Both bond lengths are close to those in corresponding end-point binaries. We attributed the residual strain to the non-vanishing distortion energy resulting from the bond length mismatch between InP and InSb bonds.
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68.55.ag Semiconductors
78.70.Dm X-ray absorption spectra

High cyclic stability of the elastocaloric effect in sputtered TiNiCu shape memory films

C. Bechtold, C. Chluba, R. Lima de Miranda, and E. Quandt

Appl. Phys. Lett. 101, 091903 (2012); http://dx.doi.org/10.1063/1.4748307 (4 pages) | Cited 2 times

Online Publication Date: 27 August 2012

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The elastocaloric effect that occurs during the stress-induced martensitic transformation in shape memory alloys is a promising mechanism in view of solid state cooling applications. It also allows for downscaling to feature sizes in the μm range, thus, being attractive for micro-cooling applications using thin film materials. In this study, elastocaloric properties of TiNi and TiNiCu films and their relation to functional fatigue were investigated. Both materials show similar effect sizes, their fatigue behavior is however different. While the temperature change in TiNi degrades by a factor of two within 150 cycles, no significant elastocaloric fatigue was found in TiNiCu.
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81.30.Kf Martensitic transformations
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
81.40.Lm Deformation, plasticity, and creep
62.20.me Fatigue
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.fg Shape-memory effect; yield stress; superelasticity

Width-to-thickness ratio dependence on photoplastic effect of ZnS nanobelt

Y. Wei, L. H. Xu, Y. W. Tao, X. J. Zheng, J. H. Yang, D. F. Zou, and S. X. Mao

Appl. Phys. Lett. 101, 091904 (2012); http://dx.doi.org/10.1063/1.4749273 (4 pages)

Online Publication Date: 28 August 2012

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Photoplastic effect (PPE) of individual ZnS nanobelt with different width-to-thickness (w/t) ratios was investigated by using a nanoindenter in conjunction with an incident ultraviolet light source system. The results show that the positive and negative PPEs are observed for the w/t ratios 4.9–9.6 and 3.2–4.1. At the peak indentation loads 20–50 μN, the positive and negative PPEs occur for the w/t ratios 4.9 and 3.2, however, they disappear at 60 μN. PPE is determined by w/t ratio not peak indentation load, and it is interpreted by the competing mechanisms of increase of Peierls barrier and radiation enhanced dislocation glide.
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62.20.fq Plasticity and superplasticity
81.40.Lm Deformation, plasticity, and creep
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
62.25.Mn Fracture/brittleness

Single-crystalline laterally graded GeSn on insulator structures by segregation controlled rapid-melting growth

Masashi Kurosawa, Yuki Tojo, Ryo Matsumura, Taizoh Sadoh, and Masanobu Miyao

Appl. Phys. Lett. 101, 091905 (2012); http://dx.doi.org/10.1063/1.4748328 (4 pages)

Online Publication Date: 28 August 2012

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Single-crystalline laterally graded GeSn-on-insulator (GeSnOI) structures are essential to achieve novel device-arrays with various direct-energy-band gaps, which can be merged with high-density Si large-scale-integrated-circuits. We investigate the seeding rapid-melting-growth of narrow stripes with a-Ge/Sn/a-Ge stacked-structures. This achieves laterally graded GeSn crystalline layers on Si substrates covered with SiO2 films. Stripe-length dependent GeSn lateral-profiles are quantitatively explained by Scheil equation, which enables precise designing of GeSn lateral-profiles. High-crystallinity GeSn stripes without dislocations or stacking faults are also demonstrated.
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81.10.Fq Growth from melts; zone melting and refining
64.75.Qr Phase separation and segregation in semiconductors

Ultra-fast calorimetry study of Ge2Sb2Te5 crystallization between dielectric layers

J. Orava, A. L. Greer, B. Gholipour, D. W. Hewak, and C. E. Smith

Appl. Phys. Lett. 101, 091906 (2012); http://dx.doi.org/10.1063/1.4748881 (4 pages) | Cited 1 time

Online Publication Date: 28 August 2012

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Phase changes in chalcogenides such as Ge2Sb2Te5 can be exploited in non-volatile random-access memory, with fast crystallization crucial for device operation. Ultra-fast differential scanning calorimetry, heating at rates up to 40 000 K s−1, has been used to study the crystallization of amorphous Ge2Sb2Te5 with and without sandwich layers of ZnS-SiO2. At heating rates up to 1000 K s−1, the sandwich layers retard crystallization, an effect attributed to crystallization-induced stress. At greater heating rates (≥5000 K s−1), and consequently higher crystallization temperatures, the stress is relaxed, and sandwich layers catalyze crystallization. Implications for memory-device performance are discussed.
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64.70.kg Semiconductors
64.70.kj Glasses
81.40.Gh Other heat and thermomechanical treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Dielectric elastomer actuators with elastomeric electrodes

Michael Bozlar, Christian Punckt, Sibel Korkut, Jian Zhu, Choon Chiang Foo, Zhigang Suo, and Ilhan A. Aksay

Appl. Phys. Lett. 101, 091907 (2012); http://dx.doi.org/10.1063/1.4748114 (5 pages)

Online Publication Date: 29 August 2012

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For many applications of dielectric elastomer actuators, it is desirable to replace the carbon-grease electrodes with stretchable, solid-state electrodes. Here, we attach thin layers of a conducting silicone elastomer to prestrained films of an acrylic dielectric elastomer and achieve voltage-actuated areal strains over 70%. The influence of the stiffness of the electrodes and the prestrain of the dielectric films is studied experimentally and theoretically.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
77.55.-g Dielectric thin films

Electrical and Fourier transform infrared properties of epitaxial SmNiO3 tensile strained thin film

Badr Torriss, Mohamed Chaker, and Joëlle Margot

Appl. Phys. Lett. 101, 091908 (2012); http://dx.doi.org/10.1063/1.4748982 (3 pages)

Online Publication Date: 29 August 2012

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We have grown epitaxial SmNiO3 thin films under tensile strain on SrTiO3 (001) substrate by pulsed laser deposition. A metal-insulator transition is found at about 394 K similar to observations made in bulk samples. The x-ray reciprocal space map suggests that the film undergoes partial strain relaxation, stabilizing the structure SmNiO3 with lower oxygen vacancies. The corresponding mid-infrared transmittance decreases when passing through the metal-insulator transition.
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73.61.Ng Insulators
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics
71.30.+h Metal-insulator transitions and other electronic transitions
81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Hard HfB2 tip-coatings for ultrahigh density probe-based storage

Noureddine Tayebi, Angel Yanguas-Gil, Navneet Kumar, Yuegang Zhang, John R. Abelson, Yoshio Nishi, Qing Ma, and Valluri R. Rao

Appl. Phys. Lett. 101, 091909 (2012); http://dx.doi.org/10.1063/1.4748983 (5 pages)

Online Publication Date: 29 August 2012

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Probe-tip mechanical wear is a fundamental issue facing probe-based storage, which can cause serious degradation of the write-read resolution over the device lifetime. HfB2 conductive coatings grown at low temperatures using chemical vapor deposition possess high mechanical properties that are ideal for this technology. Here, we show that HfB2 coated probe-tips can potentially enhance a previously demonstrated 5 km wear endurance mechanism developed using PtIr coated probe-tips to beyond 8 km, thereby increasing the lifetime of probe-based memory devices. We foresee the extension of this coating technology to other scanning probe based systems and nanoelectromechanical devices.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
62.20.Qp Friction, tribology, and hardness
81.40.Pq Friction, lubrication, and wear
68.55.at Other materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Temperature dependent recombination dynamics in InP/ZnS colloidal nanocrystals

R. Shirazi, O. Kopylov, A. Kovacs, and B. E. Kardynał

Appl. Phys. Lett. 101, 091910 (2012); http://dx.doi.org/10.1063/1.4749276 (4 pages)

Online Publication Date: 30 August 2012

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In this letter, we investigate exciton recombination in InP/ZnS core-shell colloidal nanocrystals over a wide temperature range. Over the entire range between room temperature and liquid helium temperature, multi-exponential exciton decay curves are observed and well explained by the presence of bright and dark exciton states, as well as defect states. Two different types of defect are present: one located at the core-shell interface and the other on the surface of the nanocrystal. Based on the temperature dependent contributions of all four states to the total photoluminescence signal, we estimate that the four states are distributed within a 20 meV energy band in nanocrystals that emit at 1.82 eV.
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71.35.-y Excitons and related phenomena
71.55.Ht Other nonmetals
73.20.At Surface states, band structure, electron density of states
78.55.Hx Other solid inorganic materials
79.20.Fv Electron impact: Auger emission
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Direct writing of Au nanoneedles array on glass by confined laser spinning

Yingling Yang, Dong Lin, and Gary J. Cheng

Appl. Phys. Lett. 101, 091911 (2012); http://dx.doi.org/10.1063/1.4746427 (3 pages)

Online Publication Date: 30 August 2012

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Generation of gold nanoneedles on glass by confined laser spinning was explored by using a nanosecond pulsed laser. When the coated Au thin film was irradiated under the confinement of glass, gold nanoneedles were formed by spreading the molten liquid of gold under high pressure. The mechanism of the confined laser spinning process is studied. The maximum velocity and instability of molten liquid during confined laser spinning were estimated. The diameter of nanoneedles can be controlled by changing the thickness of coated gold thin film. Large scale of gold nanoneedles can be formed by this direct writing method and collected by confined glass.
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81.15.Fg Pulsed laser ablation deposition
81.16.Mk Laser-assisted deposition
62.50.-p High-pressure effects in solids and liquids
68.55.aj Insulators
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