A Cross Correlation Chopper for Molecular Beam Modulation

Hirschy, V. L.; Aldridge, J. P.

doi:10.1063/1.1685100

Cited by 63 publications

(22 citation statements)

References 5 publications

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“…Since only the small fraction of the incident molecules are transmitted through the film, the molecular beam was modulated according to a maximum length sequence in order to improve the sensitivity. 47 The free-standing samples were prepared following the procedure described in Ref. 46.…”

Section: Scattering Of Helium On Free-standing Va-swnt Filmsmentioning

confidence: 99%

Gas–Surface Energy Exchange in Collisions of Helium Atoms with Aligned Single-Walled Carbon Nanotube Arrays

et al. 2013

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Since gas flows in micro/nano devices are dominated by the interaction of gas molecules and solid surfaces, surface modification technique is one of the critical issues for optimizing the thermal performance of these devices. In this paper, we demonstrate the successful application of vertically aligned single-walled carbon nanotubes (VA-SWNTs) as surface modification material to enhance the energy accommodation of gas molecules on surfaces. The scattering of gas molecules on quartz surfaces covered with VA-SWNTs is investigated by the molecular beam technique. The energy accommodation coefficients of helium, which tend to be small even for rough surfaces because of the large mass mismatch between helium and surface atoms, are close to unity on the modified surfaces. The measurement with the free-standing films further reveals that the high accommodation is attributed to the unique morphology of the films with high porosity, which allows gas molecules to penetrate into the films and realizes a large number of collisions with SWNTs. The result suggests that the surface modification with VA-SWNTs can be utilized for the thermal management in electric devices and micro/nano-electro-mechanical systems.

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Section: Scattering Of Helium On Free-standing Va-swnt Filmsmentioning

confidence: 99%

Gas–Surface Energy Exchange in Collisions of Helium Atoms with Aligned Single-Walled Carbon Nanotube Arrays

et al. 2013

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“…25 Particular methods for generation of pseudo-random sequences 28,29 were developed in connection with communication and encryption processes, 30 acoustics 31 , and pseudo-random chopping of a beam in time-of-flight experiments with slow neutrons [32][33][34][35][36][37] and molecular beams. [38][39][40] The maximum duty cycle (relative number of 1's and 0's) of approximately 50%…”

Section: Bpr Sequences and Arraysmentioning

confidence: 99%

“…URAs are widely used as optimal mask patterns for coded aperture imaging techniques. 26 Analogous to the time-of-flight technique based on 1D BPR sequence chopping, [32][33][34][35][36][37][38][39][40] an imaging technique based on the 2D URAs allows one to obtain a better signal-to-noise ratio, keeping the high angular resolution characteristic of a single pinhole aperture. [42][43][44] Similar to the 1D BPR sequences, the URAs possess both high throughput (50%) and a delta-function-like cyclical autocorrelation function that corresponds to a flat 2D PSD spectrum.…”

mentioning

confidence: 99%

Calibration of the modulation transfer function of surface profilometers with binary pseudo-random test standards: expanding the application range

et al. 2010

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A modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) gratings and arrays [Proc. SPIE 7077-7 (2007), Opt. Eng. 47(7), 073602-1-5 (2008)] has been proven to be an effective MTF calibration method for a number of interferometric microscopes and a scatterometer [Nucl. Instr. and Meth. A 616, 172-82 (2010]. Here we report on a significant expansion of the application range of the method. We describe the MTF calibration of a 6 inch phase shifting Fizeau interferometer. Beyond providing a direct measurement of the interferometer's MTF, tests with a BPR array surface have revealed an asymmetry in the instrument's data processing algorithm that fundamentally limits its bandwidth. Moreover, the tests have illustrated the effects of the instrument's detrending and filtering procedures on power spectral density measurements. The details of the development of a BPR test sample suitable for calibration of scanning and transmission electron microscopes are also presented. Such a test sample is realized as a multilayer structure with the layer thicknesses of two materials corresponding to BPR sequence. The investigations confirm the universal character of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.

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“…[15][16][17] The sequences are mathematically represented with 1's, which denote an open chopper slot, and 0's, which denote a closed chopper slot. The chopping associated with a cross-correlation analysis of the measured time-resolved detector signal is favored over single-shot (periodic) chopping with the duty-cycle gain factor as high as 4 N (assuming two slits on a periodic chopper), where N is the length of the pseudorandom sequence.…”

Section: Mathematical Background Of Binary Pseudo-random Grating Stanmentioning

confidence: 99%

Binary pseudo-random grating as a standard test surface for measurement of modulation transfer function of interferometric microscopes

Yashchuk

McKinney²,

Takacs

2007

Advances in Metrology for X-Ray and EUV Optics II

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TitleBinary pseudo-random grating as a standard test surface for measurement of modulation transfer function of interferometric microscopes ABSTRACTThe task of designing high performance X-ray optical systems requires the development of sophisticated X-ray scattering calculations based on rigorous information about the optics. One of the most insightful approaches to these calculations is based on the power spectral density (PSD) distribution of the surface height. The major problem of measurement of a PSD distribution with an interferometric and/or atomic force microscope arises due to the unknown Modulation Transfer Function (MTF) of the instruments. The MTF characterizes the perturbation of the PSD distribution at higher spatial frequencies. Here, we describe a new method and dedicated test surfaces for calibration of the MTF of a microscope. The method is based on use of a specially designed Binary Pseudo-random (BPR) grating. Comparison of a theoretically calculated PSD spectrum of a BPR grating with a spectrum measured with the grating provides the desired calibration of the instrumental MTF. The theoretical background of the method, as well as results of experimental investigations are presented.

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A Cross Correlation Chopper for Molecular Beam Modulation

Cited by 63 publications

References 5 publications

Gas–Surface Energy Exchange in Collisions of Helium Atoms with Aligned Single-Walled Carbon Nanotube Arrays

Gas–Surface Energy Exchange in Collisions of Helium Atoms with Aligned Single-Walled Carbon Nanotube Arrays

Calibration of the modulation transfer function of surface profilometers with binary pseudo-random test standards: expanding the application range

Binary pseudo-random grating as a standard test surface for measurement of modulation transfer function of interferometric microscopes

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