Theoretical and experimental molecular beam angular distribution studies for gas injection in ultra-high vacuum

Isnard, L.; Arès, Richard

doi:10.1016/j.jcrysgro.2008.11.088

Cited by 9 publications

(8 citation statements)

References 16 publications

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“…Even though the cosine law of emission does not apply [17,18] for all systems, this paper treats particles that are thermally accommodated by the system walls. A previous paper has shown that such conditions are experimentally attainable [6].…”

Section: A the Transport Equation Applied To Highly Rarefied Gasesmentioning

confidence: 91%

“…The starting radius is 0.95 mm, the length is 20.1 mm, and the opening half angle is 10 • . This shape was initially studied by Isnard [6] to experimentally show that the transport equation solution is valid for free molecular flow and that the impinging flux arriving on a wafer destined for epitaxial growth could then be controlled by optimizing the shape of a gas injector. However, too high a flux at the entrance illustrated the inadequacy of the free molecular flow hypothesis to describe the exiting flux.…”

Section: Controlled Gas Injection In High-vacuum Systemsmentioning

confidence: 99%

“…considering an input gas of nitrogen N 2 [6]. Then the effective intermolecular collision cross section is σ T = 4.3 × 10 −19 m 2 [22,23] andv = 475 m/s at 295 K. With Eqs.…”

Section: Controlled Gas Injection In High-vacuum Systemsmentioning

confidence: 99%

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Point-to-source path tracing Monte Carlo to compute the Clausing and distribution functions in high-vacuum systems

2017

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This paper presents an approach to simulate the free molecular flow in vacuum systems by using a Monte Carlo method for solving the Boltzmann particle transport equation with no intermolecular collisions. Sometimes referred to as a point-to-source Monte Carlo path tracing in image rendering, in this paper the name is borrowed from the thermal radiation and heat transfer field, reverse Monte Carlo path tracing. It is shown that this method provides better accuracy and stability when computing the Clausing function when compared to the standard test particle Monte Carlo method used for free molecular flow. The Clausing function leads to the distribution function of positions and velocities from which the particle density map, pressure gradient, energy flux, and other local quantities can be computed. Using reverse path tracing, the particle concentration in a conical segment is computed, and the maximal flow input is determined by calculating the mean free path at the maximum density position.

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Section: A the Transport Equation Applied To Highly Rarefied Gasesmentioning

confidence: 91%

Section: Controlled Gas Injection In High-vacuum Systemsmentioning

confidence: 99%

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Point-to-source path tracing Monte Carlo to compute the Clausing and distribution functions in high-vacuum systems

2017

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“…The injected flow-rate is precisely controlled using a pressure cell. 6 A thermal mass-flow meter ͑MFM͒ situated upstream of this cell is used for flow-rate measurement. The pumping system allows us to reach a base pressure of about 1 ϫ 10 −5 Pa. For injected flow rates of up to 4 SCCM ͑SCCM denotes cubic centimeter per minute at STP͒, the chamber pressure is measured below 0.011 Pa ensuring that the mean free path for air at room temperature is larger than the largest vessel's dimension ͑0.6 m͒.…”

Section: Methodsmentioning

confidence: 99%

“…This property can be used advantageously in our case because a fast, precise, and reliable way of calculating J along a tube's length is available to us. 6 A set of tubes with a range of length-to-radius ratio ͑l / r͒ was first selected and the corresponding wall impingement rates were obtained.…”

Section: Angular Transfer Function Of a Tubementioning

confidence: 99%

Signal enhancement strategies for angular profile measurements of gas injected in ultrahigh vacuum

Isnard

Arès

2010

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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With current trends in physical chemistry and various ultrahigh vacuum (UHV) based fabrication techniques, such as thin film deposition and epitaxy, there is a growing need to develop a precise and reliable simulation platform to predict the angular distribution of gas molecules injected in vacuum through a nozzle of a given geometry. Such models need to be validated through a systematic experimental study that clearly isolates the contributions of each parameter. For this purpose, a test platform dedicated to the measurement of the molecular beam angular profiles produced by a nozzle in UHV has been designed and built. Its main features are discussed, especially regarding its ability to produce precise and reproducible data. In order to reduce the contribution from the molecules scattered by the chamber walls to the measured flux densities and thus achieve a better signal-to-background ratio, several strategies are considered and evaluated. In particular, an innovative approach based on a direction selection tube is presented with a quantitative evaluation of its effect on the measurements. Finally a rule of thumb is proposed for the choice of the tube’s dimensions allowing a maximum background reduction while keeping the impact on the signal as small as desired.

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Molecular flux distribution from the thermal evaporation source using Monte Carlo method: The importance of interparticle collision

Hyun

Kim²,

Im³

et al. 2019

Current Applied Physics

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Theoretical and experimental molecular beam angular distribution studies for gas injection in ultra-high vacuum

Cited by 9 publications

References 16 publications

Point-to-source path tracing Monte Carlo to compute the Clausing and distribution functions in high-vacuum systems

Point-to-source path tracing Monte Carlo to compute the Clausing and distribution functions in high-vacuum systems

Signal enhancement strategies for angular profile measurements of gas injected in ultrahigh vacuum

Molecular flux distribution from the thermal evaporation source using Monte Carlo method: The importance of interparticle collision

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