Simplified neutral atom microscopy

Witham, Philip; Sánchez, Erik J.

doi:10.1109/nano.2011.6144498

Cited by 3 publications

(3 citation statements)

References 21 publications

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“…The function of this component is to select and increase the pressure contrast sensed by the detector due to scattering in some chosen direction. A discussion of this as a network of vacuum conductances is found in Witham & Sánchez (2011b). The nozzle is a sheet metal cone shape with a narrow inlet area located close to the sample.…”

Section: Improving Spatial Resolutionmentioning

confidence: 99%

Increased resolution in neutral atom microscopy

Witham

Sánchez

2012

Journal of Microscopy

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Summary The neutral atom microscope uses a beam of thermal noncharged atoms or molecules to probe an atomic surface with very low interaction energies (<70 meV). Continued optimization of the ‘pinhole’ neutral atom microscope has improved resolution to 0.35 μm. Recent images are presented demonstrating resolution and the contrast mechanisms identified so far. The future potential for sub‐100 nm resolution is discussed.

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Section: Improving Spatial Resolutionmentioning

confidence: 99%

Increased resolution in neutral atom microscopy

Witham

Sánchez

2012

Journal of Microscopy

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“…The concept of a spatially resolved helium scattering instrument was originally demonstrated in transmission by Koch et al [1], using a Fresnel zone plate to focus the atoms. The method was later extended to reflection mode by Witham and Sanchez [2], who used a pinhole to collimate the beam. The pinhole geometry has also been utilised in instruments developed by collaborating researchers in Cambridge, UK and Newcastle, Australia [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…For a zone plate, the total flux in the beam is given by F zp = ηIπ(r N ) 2 , where η is the efficiency of the zone plate and r N is its radius. By substituting and using the continuum limit approximation r N = λ f /2∆r N , where ∆r N is the size of the outermost zone, we obtain the total flux in a zone plate focused beam,…”

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confidence: 99%

A method for constrained optimisation of the design of a scanning helium microscope

et al. 2019

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We describe a method for obtaining the optimal design of a normal incidence Scanning Helium Microscope (SHeM). Scanning helium microscopy is a recently developed technique that uses low energy neutral helium atoms as a probe to image the surface of a sample without causing damage. After estimating the variation of source brightness with nozzle size and pressure, we perform a constrained optimisation to determine the optimal geometry of the instrument (i.e. the geometry that maximises intensity) for a given target resolution. For an instrument using a pinhole to form the helium microprobe, the source and atom optics are separable and Lagrange multipliers are used to obtain an analytic expression for the optimal parameters. For an instrument using a zone plate as the focal element, the whole optical system must be considered and a numerical approach has been applied. Unlike previous numerical methods for optimisation, our approach provides insight into the effect and significance of each instrumental parameter, enabling an intuitive understanding of effect of the SHeM geometry. We show that for an instrument with a working distance of 1 mm, a zone plate with a minimum feature size of 25 nm becomes the advantageous focussing element if the desired beam standard deviation is below about 300 nm.

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