14,918 research outputs found
Thermal analysis of submicron nanocrystalline diamond films
The thermal properties of sub-μm nanocrystalline diamond films in the range of 0.37–1.1 μm grown by hot filament CVD, initiated by bias enhanced nucleation on a nm-thin Si-nucleation layer on various substrates, have been characterized by scanning thermal microscopy. After coalescence, the films have been outgrown with a columnar grain structure. The results indicate that even in the sub-μm range, the average thermal conductivity of these NCD films approaches 400 W m− 1 K− 1. By patterning the films into membranes and step-like mesas, the lateral component and the vertical component of the thermal conductivity, k<sub>lateral</sub> and k<sub>vertical</sub>, have been isolated showing an anisotropy between vertical conduction along the columns, with k<sub>vertical</sub> ≈ 1000 W m− 1 K− 1, and a weaker lateral conduction across the columns, with k<sub>lateral</sub> ≈ 300 W m− 1 K− 1
Nonequilibrium quantum-impurities: from entropy production to information theory
Nonequilibrium steady-state currents, unlike their equilibrium counterparts,
continuously dissipate energy into their physical surroundings leading to
entropy production and time-reversal symmetry breaking. This letter discusses
these issues in the context of quantum impurity models driven out of
equilibrium by attaching the impurity to leads at different chemical potentials
and temperatures. We start by pointing out that entropy production is often
hidden in traditional treatments of quantum-impurity models. We then use simple
thermodynamic arguments to define the rate of entropy production. Using the
scattering framework recently developed by the authors we show that the rate of
entropy production has a simple information theoretic interpretation in terms
of the Shannon entropy and Kullback-Leibler divergence of nonequilibrium
distribution function. This allows us to show that the entropy production is
strictly positive for any nonequilibrium steady-state. We conclude by applying
these ideas to the Resonance Level Model and the Kondo model.Comment: 5 pages, 1 figure new version with minor clarification
Cavity-enhanced optical detection of carbon nanotube Brownian motion
Optical cavities with small mode volume are well-suited to detect the
vibration of sub-wavelength sized objects. Here we employ a fiber-based,
high-finesse optical microcavity to detect the Brownian motion of a freely
suspended carbon nanotube at room temperature under vacuum. The optical
detection resolves deflections of the oscillating tube down to 50pm/Hz^1/2. A
full vibrational spectrum of the carbon nanotube is obtained and confirmed by
characterization of the same device in a scanning electron microscope. Our work
successfully extends the principles of high-sensitivity optomechanical
detection to molecular scale nanomechanical systems.Comment: 14 pages, 11 figure
Alignment verification for electron beam lithography
Alignment between lithography layers is essential for device fabrication. A minor defect in a single marker can lead to incorrect alignment and this can be the source of wafer reworks. In this paper we show that this can be prevented by using extra alignment markers to check the alignment during patterning, rather than inspecting vernier patterns after the exposure is completed. Accurate vernier patterns can often only be read after pattern transfer has been carried out. We also show that by using a Penrose tile as a marker it is possible to locate the marker to about 1 nm without fully exposing the resist. This means that the marker can be reused with full accuracy, thus improving the layer to layer alignment accuracy. Lithography tool noise limits the process
Energy Spectrum Evolution of a Diffuse Field in Elastic Body Caused by Weak Nonlinearity
We study the evolution of diffuse elastodynamic spectral energy density under
the influence of weak nonlinearity. It is shown that the rate of change of this
quantity is given by a convolution of the linear energy at two frequencies.
Quantitative estimates are given for sample aluminum and fused silica blocks of
experimental interest.Comment: 9 pages, 3 figures; revised for better presentatio
An Airship Slide Rule
This report prepared for the National Advisory Committee for Aeronautics, describes an airship slide rule developed by the Gas-Chemistry Section of the Bureau of Standards, at the request of the Bureau of Engineering of the Navy Department. It is intended primarily to give rapid solutions of a few problems of frequent occurrence in airship navigation, but it can be used to advantage in solving a great variety of problems, involving volumes, lifting powers, temperatures, pressures, altitudes and the purity of the balloon gas. The rule is graduated to read directly in the units actually used in making observations, constants and conversion factors being taken care of by the length and location of the scales. It is thought that with this rule practically any problem likely to arise in this class of work can be readily solved after the user has become familiar with the operation of the rule; and that the solution will, in most cases, be as accurate as the data warrant
Pulsed Doppler lidar for the detection of turbulence in clear air
A pulsed C02 Doppler lidar system is described and demonstration tests in ground-based and airborne flight operations are discussed. As a ground-based system, it can detect wind shears in thunderstorm gust fronts to a range of 6 km. When in the airborne configuration, the lidar can detect clear air turbulence in advance of the aircraft encountering clear air turbulence. The data provided by the lidar included turbulence location and intensity with intensity being indicated by the measured spectral width which is proportional to the wind gust velocity
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