Nanocrystal seeding: A low temperature route to polycrystalline Si films

A novel method is presented for growth of polycrystalline silicon films on amorphous substrates at temperatures of 540–575 °C. Grain nucleation and grain growth are performed in two steps, using Si nanocrystals as nuclei ("seeds"). The nanocrystal seeds are produced by excimer laser photolysis of disilane in a room temperature flow cell. Film (grain) growth occurs epitaxially on the seeds in a separate thermal chemical vapor deposition (CVD) step, with growth rates 10–100 times higher than similar CVD growth rates on crystal Si. Grain size and CVD growth rates are dependent on seed coverage, for seed coverage <0.2 monolayers

Permission form synopses to improve parents' understanding of research: a randomized trial.

ObjectiveWe hypothesized that, among parents of potential neonatal research subjects, an accompanying cover sheet added to the permission form (intervention) would increase understanding of the research, when compared to a standard form (control).Study designThis pilot study enrolled parents approached for one of two index studies: one randomized trial and one observational study. A one-page cover sheet described critical study information. Families were randomized 1:1 to receive the cover sheet or not. Objective and subjective understanding and satisfaction were measured.ResultsThirty-two parents completed all measures (17 control, 15 intervention). There were no differences in comprehension score (16.8±5.7 vs 16.3±3.5), subjective understanding (median 6 vs 6.5), or overall satisfaction with consent (median 7 vs 6.5) between control and intervention groups (all P&gt;0.50).ConclusionA simplified permission form cover sheet had no effect on parents' understanding of studies for which their newborns were being recruited

Probing Light Atoms at Sub-nanometer Resolution: Realization of Scanning Transmission Electron Microscope Holography

Atomic resolution imaging in transmission electron microscopy (TEM) and scanning TEM (STEM) of light elements in electron-transparent materials has long been a challenge. Biomolecular materials, for example, are rapidly altered when illuminated with electrons. These issues have driven the development of TEM and STEM techniques that enable the structural analysis of electron beam-sensitive and weakly scattering nano-materials. Here, we demonstrate such a technique, STEM holography, capable of absolute phase and amplitude object wave measurement with respect to a vacuum reference wave. We use an amplitude-dividing nanofabricated grating to prepare multiple spatially separated electron diffraction probe beams focused at the sample plane, such that one beam transmits through the specimen while the others pass through vacuum. We raster-scan the diffracted probes over the region of interest. We configure the post specimen imaging system of the microscope to diffraction mode, overlapping the probes to form an interference pattern at the detector. Using a fast-readout, direct electron detector, we record and analyze the interference fringes at each position in a 2D raster scan to reconstruct the complex transfer function of the specimen, t(x). We apply this technique to image a standard target specimen consisting of gold nanoparticles on a thin amorphous carbon substrate, and demonstrate 2.4 angstrom resolution phase images. We find that STEM holography offers higher phase-contrast of the amorphous material while maintaining Au atomic lattice resolution when compared with high angle annular dark field STEM.Comment: 9 pages, 5 figures in main text, 1 supplemental figure in the appendi

Coaxial Nickel Poly(Vinylidene Fluoride Trifluoroethylene) Nanowires for Magnetoelectric Applications

Magnetoelectric (ME) composite materials, in which the coupling between magnetostricitve and piezoelectric effects is achieved, are potential candidates for multifunctional devices where the interplay between electrical, magnetic and mechanical properties of these structures can be fully exploited. Nanostructured composites are particularly interesting due to the enhancement of ME coupling expected at the nanoscale. However, direct studies of ME coupling in nanocomposites by scanning probe techniques are rare due to the complex interplay of forces at play, including those arising from electrostatic, magnetic and electromechanical interactions. In this work, the ME coupling of coaxial nickel - polyvinylidene fluoride trifluoroethylene [Ni-P(VDF-TrFE)] composite nanowires, fabricated by a scalable template-wetting based technique, is studied using a systematic sequence of scanning probe techniques. Individual ME nanowires were subjected to an electric field sufficient for ferroelectric poling in piezo-response force microscopy (PFM) mode, while magnetic force microscopy (MFM) was used to measure localised changes in magnetization as a result of electrical poling. Kelvin probe force microscopy (KPFM) measurements of surface potential were conducted to eliminate for the effect of contact potential differences during these measurements. An inverse, static, magnetoelectric coupling coefficient of ~1 x 10-11 s m-1 was found in our coaxial nanocomposite nanowires, comparable to other types of planar composites studied in this work, despite having an inferior piezoelectric-to-magnetostrictive volume ratio. The efficient ME coupling in our coaxial nanowires is attributed to the larger surface-to-volume interfacial contact between Ni and P(VDF-TrFE), and is promising for future integration into ME composite devices such as magnetic field sensors or energy harvesters

Synthesizing Skyrmion Molecules in Fe-Gd Thin Films

We show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit room-temperature skyrmion molecules, or a pair of like-polarity, opposite-helicity skyrmions. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.Comment: 15 pages, 6 figures. Accepted for publication in Applied Physics Letter

Interpretable and efficient contrast in scanning transmission electron microscopy with a diffraction grating beamsplitter

Efficient imaging of biomolecules, 2D materials and electromagnetic fields depends on retrieval of the phase of transmitted electrons. We demonstrate a method to measure phase in a scanning transmission electron microscope using a nanofabricated diffraction grating to produce multiple probe beams. The measured phase is more interpretable than phase-contrast scanning transmission electron microscopy techniques without an off-axis reference wave, and the resolution could surpass that of off-axis electron holography. We apply the technique to image nanoparticles, carbon sub- strates and electric fields. The contrast observed in experiments agrees well with contrast predicted in simulations

Optimizing Multi-Photon Fluorescence Microscopy Light Collection from Living Tissue by Non-Contact Total Emission Detection (TEDII)

Farrando Sicilia, Jordi; Fuente Fuente, Carlo