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29 Dec 2008

Volume 93, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 93, 261101 (2008); http://dx.doi.org/10.1063/1.3053074 (3 pages)

Takashi Fujikura, Osamu Matsuda, Dieter M. Profunser, Oliver B. Wright, Jeremy Masson, and Sylvain Ballandras
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Subnanosecond time-resolved x-ray measurements using an organic-inorganic perovskite scintillator

S. Kishimoto, K. Shibuya, F. Nishikido, M. Koshimizu, R. Haruki, and Y. Yoda

Appl. Phys. Lett. 93, 261901 (2008); http://dx.doi.org/10.1063/1.3059562 (3 pages) | Cited 2 times

Online Publication Date: 29 December 2008

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We have developed a fast x-ray detector using an organic-inorganic perovskite scintillator of phenethylamine lead bromide (PhE-PbBr4). The scintillator had a dominant light emission with a fast decay time of 9.9 ns. An x-ray detector equipped with a 0.9-mm-thick PhE-PbBr4 crystal was used to detect nuclear resonant scattering in 61Ni (the first excited level: 67.41 keV; lifetime: 7.6 ns) by using synchrotron radiation. With this detector, we could successfully record the decaying gamma rays emitted from 61Ni with a time resolution of 0.7 ns (full width at half maximum) and a relatively high detection efficiency of 24%.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
29.40.Mc Scintillation detectors

Dynamic delamination of patterned thin films

Soma S. V. Kandula, Phuong Tran, Philippe H. Geubelle, and Nancy R. Sottos

Appl. Phys. Lett. 93, 261902 (2008); http://dx.doi.org/10.1063/1.3056639 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2008

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We investigate laser-induced dynamic delamination of a patterned thin film on a substrate. Controlled delamination results from our insertion of a weak adhesion region beneath the film. The inertial forces acting on the weakly bonded portion of the film lead to stable propagation of a crack along the film/substrate interface. Through a simple energy balance, we extract the critical energy for interfacial failure, a quantity that is difficult and sometimes impossible to characterize by more conventional methods for many thin film/substrate combinations.
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68.60.Bs Mechanical and acoustical properties
68.55.J- Morphology of films
62.20.mt Cracks
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

TixSi1−xO2 optical coatings with tunable index and their response to intense subpicosecond laser pulse irradiation

D. Nguyen, L. A. Emmert, I. V. Cravetchi, M. Mero, W. Rudolph, M. Jupe, M. Lappschies, K. Starke, and D. Ristau

Appl. Phys. Lett. 93, 261903 (2008); http://dx.doi.org/10.1063/1.3050536 (3 pages) | Cited 8 times

Online Publication Date: 29 December 2008

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Ion-beam sputtered TixSi1−xO2 binary-oxide films of high optical quality with tunable bandgap and refractive index were produced using zone targets. The suitability of the films for high-power subpicosecond laser applications is explored by laser breakdown measurements. The observed scaling laws of the single-pulse breakdown threshold—a power law with respect to pulse duration and a linear law with respect to bandgap energy—are similar to results obtained with high-quality simple oxides. The single- and multiple-pulse breakdown behaviors of these binary films indicate only slightly larger defect densities than found in simple oxides.
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78.66.Nk Insulators
42.79.Wc Optical coatings
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Photoluminescence dynamics of exciton-exciton scattering in a lightly alloyed InGaN thin film

M. Nakayama and K. Sakaguchi

Appl. Phys. Lett. 93, 261904 (2008); http://dx.doi.org/10.1063/1.3054166 (3 pages)

Online Publication Date: 30 December 2008

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We have investigated the photoluminescence (PL) dynamics of a lightly alloyed In0.02Ga0.98N thin film under intense excitation conditions at 10 K. In the In0.02Ga0.98N thin film, a PL band due to exciton-exciton scattering, the so-called P band, appears with a thresholdlike nature in the excitation-power region higher than ∼ 3 μJ/cm2. Under the condition that the exciton-exciton scattering occurs, the PL-decay profile consists of a fast decay component of the P band (of the order of 10 ps) and a slow decay component of a localized exciton band. The decay time of the P band gradually shortens with increasing excitation power. The change in the decay time can be explained qualitatively by the photon-like characteristics of the lower polariton branch that is the final state of the P emission. Furthermore, we have clearly observed the temporal change in the peak energy of the P band, which reflects an effective temperature of the excitonic system. The energy shift of the P band suggests that the P emission process reaches equilibrium with the lattice temperature after ∼ 100 ps.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
71.35.-y Excitons and related phenomena

Influence of molten status on nanoquasicrystalline-forming Zr-based metallic glasses

Cang Fan, D. Chen, P. K. Liaw, H. Choo, C. Benmore, J. Siewenie, G. L. Chen, J. X. Xie, and C. T. Liu

Appl. Phys. Lett. 93, 261905 (2008); http://dx.doi.org/10.1063/1.3046118 (3 pages) | Cited 1 time

Online Publication Date: 31 December 2008

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Quasicrystals, formed during the primary crystallization stage of annealing Zr70−XCu25Pt5AlX metallic glasses, decrease in size from 100 to 5 nm as the Al content is increased from 8 to 10 at. %. The glass transition and crystallization processes during annealing at fixed heating rate were found to be influenced by the thermal history of the melt. Pair distribution function analyses of neutron scattering data revealed that the broad peak from the nearest atomic pairs separates into multiple peaks with lower melt quenching temperatures (TL). These results suggest that the short-range order is enhanced with decreased TL. Such ordered regions remain in the glass upon quenching and contribute to nanoquasicrystal formation upon heating.
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61.44.Br Quasicrystals
61.43.Fs Glasses
64.70.Nd Structural transitions in nanoscale materials
64.70.kj Glasses
64.70.kd Metals and alloys
81.40.Gh Other heat and thermomechanical treatments
64.70.P- Glass transitions of specific systems

Nanolubrication of poly(methyl methacrylate) films on Si for microelectromechanical systems applications

N. Satyanarayana, K. H. Lau, and S. K. Sinha

Appl. Phys. Lett. 93, 261906 (2008); http://dx.doi.org/10.1063/1.3062847 (3 pages) | Cited 6 times

Online Publication Date: 31 December 2008

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Polymers, such as poly(methyl methacrylate) (PMMA), are important structural materials for microsystems because of their excellent mechanical properties; however, they suffer from severe problems of adhesion, friction, and wear [ B. Bhushan, J. N. Israelachvili, and U. Landman, Nature (London) 374, 607 (1995) ]. We report a simple process of O2 plasma treatment on a PMMA film, followed by overcoating with an ultrathin layer of perfluoropolyether (PFPE) which improved tribological performance of the film. O2 plasma on PMMA film has formed unique wavy nanotextured surface and increased the hardness and the elastic modulus of the film, which, together with the nanolurbication by PFPE, has increased the wear life of PMMA film by more than five orders of magnitude.
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68.60.Bs Mechanical and acoustical properties
61.46.-w Structure of nanoscale materials
81.40.Pq Friction, lubrication, and wear
68.55.am Polymers and organics
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
62.20.Qp Friction, tribology, and hardness

Work softening and annealing hardening of deformed nanocrystalline nickel

X. Y. Zhang, Q. Liu, X. L. Wu, and A. W. Zhu

Appl. Phys. Lett. 93, 261907 (2008); http://dx.doi.org/10.1063/1.3062849 (3 pages) | Cited 5 times

Online Publication Date: 31 December 2008

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We reported that work softening takes place during room-temperature rolling of nanocrystalline Ni at an equivalent strain of around 0.30. The work softening corresponds to a strain-induced phase transformation from a face-centered cubic (fcc) to a body-centered cubic (bcc) lattice. The hardness decreases with increasing volume fraction of the bcc phase. When the deformed samples are annealed at 423 K, a hardening of the samples takes place. This hardening by annealing can be attributed to a variety of factors including the recovery transformation from the bcc to the fcc phase, grain boundary relaxation, and retardation of dislocation gliding by microtwins.
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81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
64.70.kd Metals and alloys
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
61.72.Mm Grain and twin boundaries
81.40.Lm Deformation, plasticity, and creep

Lattice parameters, deviations from Vegard’s rule, and E2 phonons in InAlN

V. Darakchieva, M.-Y. Xie, F. Tasnádi, I. A. Abrikosov, L. Hultman, B. Monemar, J. Kamimura, and K. Kishino

Appl. Phys. Lett. 93, 261908 (2008); http://dx.doi.org/10.1063/1.3056656 (3 pages) | Cited 9 times

Online Publication Date: 31 December 2008

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The lattice parameters of InxAl1−xN in the whole compositional range are studied using first-principle calculations. Deviations from Vegard’s rule are obtained via the bowing parameters, δa = 0.0412±0.0039 Å and δc = −0.060±0.010 Å, which largely differ from previously reported values. Implications of the observed deviations from Vegard’s rule on the In content extracted from x-ray diffraction are discussed. We also combine these results with x-ray diffraction and Raman scattering studies on InxAl1−xN nanocolumns with 0.627 ⩽ x ⩽ 1 and determine the E2 phonon frequencies versus In composition in the scarcely studied In-rich compositional range.
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61.66.Fn Inorganic compounds
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
71.15.-m Methods of electronic structure calculations
78.30.Er Solid metals and alloys

Poly(phenylene ethynylene)-coated aligned ZnO nanorod arrays for 2,4,6-trinitrotoluene detection

Defeng Zhu, Qingguo He, Huimin Cao, Jiangong Cheng, Songlin Feng, Yuansen Xu, and Tong Lin

Appl. Phys. Lett. 93, 261909 (2008); http://dx.doi.org/10.1063/1.3063045 (3 pages) | Cited 5 times

Online Publication Date: 31 December 2008

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The structure of ZnO nanorods coated with fluorescent polymer poly(phenylene ethynylene) (PPE) have been fabricated for 2,4,6-trinitrotoluene (TNT) detection. In this structure, hydrothermally synthesized crystalline ZnO nanorod arrays were used as waveguides and supporting materials for the TNT sensitive polymer, PPE. The evanescent-wave guiding property of the ZnO nanorod waveguide considerably increased fluorescence intensity. The space between the adjacent nanorods and the larger surface-to-volume ratio of the nanorods enhanced the fluorescence response (quenching) to TNT vapor. This work will contribute to design of combining ZnO nanorod arrays with a functional polymer for sensor applications.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
81.07.Bc Nanocrystalline materials
42.79.Gn Optical waveguides and couplers

Irreversibility in cooling and heating processes in the magnetocaloric MnAs and alloys

A. L. Lima Sharma, S. Gama, A. A. Coelho, and A. de Campos

Appl. Phys. Lett. 93, 261910 (2008); http://dx.doi.org/10.1063/1.3058712 (3 pages) | Cited 3 times

Online Publication Date: 31 December 2008

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Irreversibility of adiabatic processes in the magnetocaloric MnAs and alloys is presented here. We used a differential scanning calorimeter to record the heat flux as a function of the temperature and applied field for MnAs (Mn,X)As, where X stands for Fe or Cu in 0.6% of doping. We extracted the latent heat and entropy in a cycle. In the cooling process, we observed that SMnc>SFec>SCuc, and for the heating process, SFeh ≈ SMnh>SCuh. The difference in the entropy obtained between processes was found to be as high as 37%.
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75.30.Sg Magnetocaloric effect, magnetic cooling
61.72.up Other materials
65.40.G- Other thermodynamical quantities

First-principles investigation of intrinsic defects and (N, O) impurity atom stimulated Al vacancy in Ti2AlC

Ting Liao, Jingyang Wang, and Yanchun Zhou

Appl. Phys. Lett. 93, 261911 (2008); http://dx.doi.org/10.1063/1.3058718 (3 pages) | Cited 6 times

Online Publication Date: 31 December 2008

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We use first-principles calculations to study the energetics of intrinsic defects in Ti2AlC and the effect of N or O impurity atoms on the generation of Al vacancies. The insertion of impurity atoms lowers the vacancy formation energy of its neighboring Al. The formation of Al vacancies is related to the experimental observations of growth of AlN or Al2O3 nanowires and nanofibers on the surface of Ti2AlC. Since the growth of these nanostructures is controlled by the generation and migration of intrinsic defects, we propose that a tunable method for synthesis of such nanostructures is possible by controlling impurities.
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61.72.jd Vacancies
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing

Pt redistribution during Ni(Pt) silicide formation

J. Demeulemeester, D. Smeets, C. Van Bockstael, C. Detavernier, C. M. Comrie, N. P. Barradas, A. Vieira, and A. Vantomme

Appl. Phys. Lett. 93, 261912 (2008); http://dx.doi.org/10.1063/1.3058719 (3 pages) | Cited 14 times

Online Publication Date: 31 December 2008

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We report on a real-time Rutherford backscattering spectrometry study of the erratic redistribution of Pt during Ni silicide formation in a solid phase reaction. The inhomogeneous Pt redistribution in Ni(Pt)Si films is a consequence of the low solubility of Pt in Ni2Si compared to NiSi and the limited mobility of Pt in NiSi. Pt further acts as a diffusion barrier and resides in the Ni2Si grain boundaries, significantly slowing down the Ni2Si and NiSi growth kinetics. Moreover, the observed incorporation of a large amount of Pt in the NiSi seeds indicates that Pt plays a major role in selecting the crystallographic orientation of these seeds and thus in the texture of the resulting Ni1−xPtxSi film.
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68.55.jm Texture
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
66.30.Fq Self-diffusion in metals, semimetals, and alloys
64.75.Bc Solubility
68.55.J- Morphology of films
61.72.Mm Grain and twin boundaries
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