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  • 1
    Online Resource
    Online Resource
    Grafted polymer chains suppress nanoparticle diffusion in athermal polymer melts
    AIP Publishing ; 2017
    In:  The Journal of Chemical Physics Vol. 146, No. 20 ( 2017-05-28)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 146, No. 20 ( 2017-05-28)
    Abstract: We measure the center-of-mass diffusion of poly(methyl methacrylate) (PMMA)-grafted nanoparticles (NPs) in unentangled to slightly entangled PMMA melts using Rutherford backscattering spectrometry. These grafted NPs diffuse ∼100 times slower than predicted by the Stokes-Einstein relation assuming a viscosity equal to bulk PMMA and a hydrodynamic NP size equal to the NP core diameter, 2Rcore = 4.3 nm. This slow NP diffusion is consistent with an increased effective NP size, 2Reff ≈ 20 nm, nominally independent of the range of grafting density and matrix molecular weights explored in this study. Comparing these experimental results to a modified Daoud-Cotton scaling estimate for the brush thickness as well as dynamic mean field simulations of polymer-grafted NPs in athermal polymer melts, we find that 2Reff is in quantitative agreement with the size of the NP core plus the extended grafted chains. Our results suggest that grafted polymer chains of moderate molecular weight and grafting density may alter the NP diffusion mechanism in polymer melts, primarily by increasing the NP effective size.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.4982216
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 2
    Online Resource
    Online Resource
    A machine learning photon detection algorithm for coherent x-ray ultrafast fluctuation analysis
    AIP Publishing ; 2022
    In:  Structural Dynamics Vol. 9, No. 5 ( 2022-09-01)
    Details
    In: Structural Dynamics, AIP Publishing, Vol. 9, No. 5 ( 2022-09-01)
    Abstract: X-ray free electron laser experiments have brought unique capabilities and opened new directions in research, such as creating new states of matter or directly measuring atomic motion. One such area is the ability to use finely spaced sets of coherent x-ray pulses to be compared after scattering from a dynamic system at different times. This enables the study of fluctuations in many-body quantum systems at the level of the ultrafast pulse durations, but this method has been limited to a select number of examples and required complex and advanced analytical tools. By applying a new methodology to this problem, we have made qualitative advances in three separate areas that will likely also find application to new fields. As compared to the “droplet-type” models, which typically are used to estimate the photon distributions on pixelated detectors to obtain the coherent x-ray speckle patterns, our algorithm achieves an order of magnitude speedup on CPU hardware and two orders of magnitude improvement on GPU hardware. We also find that it retains accuracy in low-contrast conditions, which is the typical regime for many experiments in structural dynamics. Finally, it can predict photon distributions in high average-intensity applications, a regime which up until now has not been accessible. Our artificial intelligence-assisted algorithm will enable a wider adoption of x-ray coherence spectroscopies, by both automating previously challenging analyses and enabling new experiments that were not otherwise feasible without the developments described in this work.
    Type of Medium: Online Resource
    ISSN: 2329-7778
    URL: Article
    DOI: 10.1063/4.0000161
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2758684-4
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  • 3
    Online Resource
    Online Resource
    Demonstration of genuine surface inversion for the p/n-In0.3Ga0.7Sb-Al2O3 MOS system with in situ H2 plasma cleaning
    AIP Publishing ; 2019
    In:  Applied Physics Letters Vol. 115, No. 23 ( 2019-12-02)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 115, No. 23 ( 2019-12-02)
    Abstract: The results of an investigation into the impact of in situ H2 plasma exposure on the electrical properties of the p/n-In0.3 Ga0.7 Sb-Al2O3 interface are presented. Samples were processed using a clustered inductively coupled plasma reactive ion etching and atomic layer deposition tool. Metal oxide semiconductor capacitors were fabricated subsequent to H2 plasma processing and Al2O3 deposition, and the corresponding capacitance-voltage and conductance-voltage measurements were analyzed quantitatively via the simulation of an equivalent circuit model. Interface state (Dit) and border trap (Nbt) densities were extracted for samples subjected to the optimal process, with a minimum Dit of 1.73×1012 eV−1 cm−2 located at ∼110 meV below the conduction band edge and peak Nbt approximately aligned with the valence and conduction band edges of 3×1019 cm−3 and 6.5×1019 cm−3, respectively. Analysis of the inversion response in terms of the extraction of the activation energy of minority carriers in inversion (p-type) and the observation of characteristics that pertain to minority carriers being supplied from an external inversion region (n-type) unequivocally demonstrate that the Fermi level is unpinned and that genuine surface inversion is observed for both doping polarities.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.5122731
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 4
    Online Resource
    Online Resource
    Association of two semiflexible polyelectrolytes by interchain linkers: Theory and simulations
    AIP Publishing ; 2002
    In:  The Journal of Chemical Physics Vol. 117, No. 1 ( 2002-07-01), p. 462-480
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 117, No. 1 ( 2002-07-01), p. 462-480
    Abstract: The aggregation of two highly charged semiflexible polyelectrolytes in the presence of generalized linkers is studied theoretically. This model provides insight into biological processes such as DNA condensation and F-actin self-assembly induced by either multivalent counterions or bundling proteins. The interplay between the bending rigidity of the chains and their electrostatic interactions leads to an effective interlinker interaction that is repulsive at large distances and attractive at short ones. We find a rounded phase transition from a dilute linker gas where the chains form large loops to a dense disordered linker fluid where the chains are almost parallel. The onset of chain pairing occurs as soon as the free energy of a pair of chains becomes lower than that of two isolated chains and is located well within the crossover regime between the two linker phases. Our main findings are confirmed by molecular dynamics simulations of two semiflexible charged chains in a mixture of monovalent and polyvalent counterions. This simple model allows us to recover qualitative features of experimental aggregation diagrams of DNA and F-actin and can also be used to study DNA denaturation.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1481382
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2002
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 5
    Online Resource
    Online Resource
    Measurement of built-in electrical potential in III–V solar cells by scanning Kelvin probe microscopy
    AIP Publishing ; 2003
    In:  Journal of Applied Physics Vol. 93, No. 12 ( 2003-06-15), p. 10035-10040
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 93, No. 12 ( 2003-06-15), p. 10035-10040
    Abstract: We report on direct measurements of the built-in electrical potential in III–V semiconductor-based solar cell devices by using scanning Kelvin probe microscopy. Potential profiles on cross sections of the devices were measured quantitatively and spatially resolved in open and short circuits, under and without illuminations, with selective photon energies matching band gaps of the junctions. The measurements provide valuable information about the electrical properties of the devices, and are useful for understanding the performance of solar cells. On a GaInP2-single junction cell, two potential features were measured and were assigned to the p-n junction and the potential barrier at the interface between the GaInP2 base layer and the GaAs substrate. The potential on the p-n junction is photoactive, and that on the GaInP2/GaAs interface is photoinactive. On a GaInP2/GaAs tandem cell, two potential features were measured near the top and the bottom p-n junctions. When the sample was illuminated by light with photon energies larger than the band gap of the top junction, in the condition of short circuit, a potential peak appeared on the boundary between the bottom cell and tunnel junction due to charge accumulations on the bottom junction.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1573736
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2003
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 6
    Online Resource
    Online Resource
    A software-controlled analog random pattern generator for space-borne detector simulation
    AIP Publishing ; 1996
    In:  Review of Scientific Instruments Vol. 67, No. 12 ( 1996-12-01), p. 4369-4379
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 67, No. 12 ( 1996-12-01), p. 4369-4379
    Abstract: This article describes a user-controlled detector simulator to aid development of the grazing incidence spectrometer (GIS), which forms part of the coronal diagnostic spectrometer on-board the solar and heliospheric observatory. The simulator was a vital element in carrying out full range tests of the GIS processing electronics in the absence of real detectors, including extreme conditions not easily achievable by other means. With a large degree of flexibility, the simulator provides a wide range of characteristics of output events of realistic shapes. Although the simulator was designed specifically to simulate the spiral anode as used by the GIS, the design is applicable to any three channel detector system and has since been used for the FONEMA instrument for the Russian Mars96 mission. The simulator functionality, performance parameters, software and hardware design, and the overall grounding scheme are presented. The simulator performance with some test results are also discussed.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.1147538
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1996
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 7
    Online Resource
    Online Resource
    Direct measurement of electrical potentials in GaInP2 solar cells
    AIP Publishing ; 2002
    In:  Applied Physics Letters Vol. 81, No. 14 ( 2002-09-30), p. 2569-2571
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 81, No. 14 ( 2002-09-30), p. 2569-2571
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.1509114
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2002
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 8
    Online Resource
    Online Resource
    The effect of boron diffusions on the defect density and recombination at the (111) silicon-silicon oxide interface
    AIP Publishing ; 2008
    In:  Applied Physics Letters Vol. 92, No. 12 ( 2008-03-24)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 92, No. 12 ( 2008-03-24)
    Abstract: A combination of electron paramagnetic resonance (EPR) and minority carrier lifetime measurements is used to unambiguously demonstrate that the presence of a B diffusion layer at the surface of oxidized Si (111) wafers causes a significant increase in the interface defect density as well as interface recombination, compared to undiffused surfaces. EPR measurements show a nearly three-fold increase in the Pb center density, while the lifetime measurements indicate an increase in surface recombination activity by a factor of more than two, for B diffused samples with a sheet resistance of ∼250Ω∕◻◻.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.2903698
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 9
    Online Resource
    Online Resource
    Anisotropy of light extraction from two-dimensional photonic crystal light-emitting diodes
    AIP Publishing ; 2007
    In:  Applied Physics Letters Vol. 91, No. 12 ( 2007-09-17)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 91, No. 12 ( 2007-09-17)
    Abstract: Anisotropic light extraction of photonic crystal (PhC) light-emitting diodes in the azimuthal direction has been investigated with an annular structure of triangular PhC lattice. The optical images of the photoluminescence light extraction are obtained with laser excitation. For increasing lattice constant, sixfold symmetric patterns with varying numbers of petals in multiples of six are observed and analyzed. A map of the anisotropy for various lattice constants and numerical apertures is constructed. Several features of light propagations associated with the PhC are observed including the focusing and collimating behaviors.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.2789399
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2007
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 10
    Online Resource
    Online Resource
    Spin-degenerate surface and the resonant spin lifetime transistor in wurtzite structures
    AIP Publishing ; 2010
    In:  Journal of Applied Physics Vol. 108, No. 8 ( 2010-10-15)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 108, No. 8 ( 2010-10-15)
    Abstract: Spin-splitting energies of wurtzite AlN and InN are calculated using the linear combination of atomic orbital method, and the data are analyzed utilizing the two-band k⋅p model. It is found that in the k⋅p scheme, a spin-degenerate surface exists in the wurtzite Brillouin zone. Consequently, the D’yakonov-Perel’ spin relaxation mechanism can be effectively suppressed for all spin components in the [001]-grown wurtzite quantum wells (QWs) at a resonant condition through application of appropriate strain or a suitable gate bias. Therefore, wurtzite QWs (e.g., InGaN/AlGaN and GaN/AlGaN) are potential structures for spintronic devices such as the resonant spin lifetime transistor.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.3484042
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2010
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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