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result(s) for
"Rooks, Michael"
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Ultra-high-density phase-change storage and memory
Phase-change storage is widely used in optical information technologies (DVD, CD-ROM and so on), and recently it has also been considered for non-volatile memory applications. This work reports advances in thermal data recording of phase-change materials. Specifically, we show erasable thermal phase-change recording at a storage density of 3.3 Tb inch
−2
, which is three orders of magnitude denser than that currently achievable with commercial optical storage technologies. We demonstrate the concept of a thin-film nanoheater to realize ultra-small heat spots with dimensions of less than 50 nm. Finally, we show in a proof-of-concept demonstration that an individual thin-film heater can write, erase and read the phase of these storage materials at competitive speeds. This work provides important stepping stones for a very-high-density storage or memory technology based on phase-change materials.
Journal Article
Josâe Parlâa : segmented realities
Segmented realities' is a group of five paintings and ten sculptural paintings by Jose Parlâa that suggest cultural fragments salvaged from urban sites that have experienced social and cultural upheaval and transformation. As do segments of walls in Havana, New York, London, or the Berlin wall, Parlâa's sculptures bear witness to waves of history that seem to be inscribed on their surfaces, told in an expressive and poetic language of the city. These works act as palimpsests, surfaces bearing layers of marks, on which ensuing generations might imagine their own manifestos and declarations of selfhood. Exhibition: High Museum of Art, Atlanta, USA (12.12.2014-24.05.2015).
Book
The beginning of heaven and Earth has no name
Heinz von Foerster was the inventor of second-order cybernetics, which recognizes the investigator as part of the system he is investigating. The Beginning of Heaven and Earth Has No Name provides an accessible, nonmathematical, and comprehensive overview of von Foerster's cybernetic ideas and of the philosophy latent within them. It distills concepts scattered across the lifework of this scientific polymath and influential interdisciplinarian. At the same time, as a book-length interview, it does justice to von Foerster's elan as a speaker and improviser, his skill as a raconteur. Developed from a week-long conversation between the editors and von Foerster near the end of his life, this work playfully engages von Foerster in developing the difference his notion of second-order cybernetics makes for topics ranging from emergence, life, order, and thermodynamics to observation, recursion, cognition, perception, memory, and communication. The book gives an English-speaking audience a new ease of access to the rich thought and generous spirit of this remarkable and protean thinker.
eBook
Electron-phonon cooling in large monolayer graphene devices
We present thermal measurements of large area (over \\(1,000\\)~\\(\\mu\\)m\\(^2\\)) monolayer graphene samples at cryogenic temperatures to study the electron-phonon thermal conductivity of graphene. By using two large samples with areas which differ by a factor of 10, we are able to clearly show the area dependence of the electron-phonon cooling. We find that, at temperatures far below the Bloch-Gruneisen temperature \\(T_\\mathrm{BG}\\), the electron-phonon cooling power is accurately described by the \\(T^4\\) temperature dependence predicted for clean samples. Using this model, we are able to extract a value for the electron-phonon coupling constant as a function of gate voltage, and the graphene electron-lattice deformation potential. We also present results for thermal conductance at higher temperatures, above \\(T_\\mathrm{BG}/4\\), for which the clean limit no longer applies. In this regime we find a cooling power which is accurately described qualitatively, but not quantitatively, by a model which predicts the emission of very high energy phonons through a disorder-assisted mechanism.
Paper
First operation of a multi-channel Q-Pix prototype: measuring transverse electron diffusion in a gas time projection chamber
We report measurements of the transverse diffusion of electrons in P-10 gas (90% Ar, 10% CH4) in a laboratory-scale time projection chamber (TPC) utilizing a novel pixelated signal capture and digitization technique known as Q-Pix. The Q-Pix method incorporates a precision switched integrating transimpedance amplifier whose output is compared to a threshold voltage. Upon reaching the threshold, a comparator sends a 'reset' signal, initiating a discharge of the integrating capacitor. The time difference between successive resets is inversely proportional to the average current at the pixel in that time interval, and the number of resets is directly proportional to the total collected charge. We developed a 16-channel Q-Pix prototype fabricated from commercial off-the-shelf components and coupled them to 16 concentric annular anode electrodes to measure the spatial extent of the electron swarm that reaches the anode after drifting through the uniform field of the TPC. The swarm is produced at a gold photocathode using pulsed UV light. The measured transverse diffusion agrees with simulations in PyBoltz across a range of operating pressures (200-1500 Torr). These results demonstrate that a Q-Pix readout can successfully reconstruct the ionization topology in a TPC.
Paper
Adiabatic embedment of nanomechanical resonators in photonic microring cavities
We report a circuit cavity optomechanical system in which a nanomechanical resonator is adiabatically embedded inside an optical ring resonator with ultralow transition loss. The nanomechanical device forms part of the top layer of a horizontal silicon slot ring resonator, which enables dispersive coupling to the dielectric substrate via a tapered nanogap. Our measurements show nearly uncompromised optical quality factors (Q) after the release of the mechanical beam.
Paper
Lasing in localized modes of a slow light photonic crystal waveguide
We demonstrate lasing in GaAs photonic crystal waveguides with InAs quantum dots as gain medium. Structural disorder is present due to fabrication imperfection and causes multiple scat- tering of light and localization of light. Lasing modes with varying spatial extend are observed at random locations along the guide. Lasing frequencies are determined by the local structure and occur within a narrow frequency band which coincides with the slow light regime of the waveguide mode. The three-dimensional numerical simulation reveals that the main loss channel for lasing modes located away from the waveguide end is out-of-plane scattering by structural disorder.
Paper
Tunable superconducting nanoinductors
We characterize inductors fabricated from ultra-thin, approximately 100 nm wide strips of niobium (Nb) and niobium nitride (NbN). These nanowires have a large kinetic inductance in the superconducting state. The kinetic inductance scales linearly with the nanowire length, with a typical value of 1 nH/um for NbN and 44 pH/um for Nb at a temperature of 2.5 K. We measure the temperature and current dependence of the kinetic inductance and compare our results to theoretical predictions. We also simulate the self-resonant frequencies of these nanowires in a compact meander geometry. These nanowire inductive elements have applications in a variety of microwave frequency superconducting circuits.
Paper