Neutral atom and molecule focusing using a Fresnel zone plate

Reisinger, T.; Holst, Bodil

doi:10.1116/1.2987955

Cited by 23 publications

(11 citation statements)

References 25 publications

(28 reference statements)

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“…Much effort has been devoted in recent years to the development of a scanning helium-atom microscope (SHeAM), [1][2][3][4] in which a focused beam of neutral He atoms is used as imaging probe. In fact, the first micrograph using helium atoms as an imaging probe has been reported recently.…”

Section: Introductionmentioning

confidence: 99%

Helium reflectivity and Debye temperature of graphene grown epitaxially on Ru(0001)

et al. 2011

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It is shown that the surface of an epitaxial graphene monolayer grown on Ru(0001) could be used as a quite efficient external mirror for He-atom microscopy, with a specular reflectivity of 20% of the incident beam. Furthermore, the system is stable up to 1150 K, and the He reflectivity remains almost unchanged after exposure to air. Additionally, the high reflectivity for H 2 molecules (11%) opens up the development of a H 2 microprobe suitable for lithography. The Debye temperature for this epitaxial graphene monolayer has been determined from a study of the temperature dependence of the He specular intensity as a function of incident parameters. A value of 1045 K has been obtained, which is much higher than the 590 K reported for graphite under similar conditions, and close to the value of 1287 K calculated for isolated graphene.

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Section: Introductionmentioning

confidence: 99%

Helium reflectivity and Debye temperature of graphene grown epitaxially on Ru(0001)

et al. 2011

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“…The focused spot sizes were evaluated following the procedure originally introduced in [18] and further developed in [25]: A (25 ± 2) µm wide slit is scanned across the focused spot in sub-micron steps (0.1 µm). As the slit moves across the spot, the measured intensity rises and based on this rise the spot size can be determined by a deconvolution of the measurements with a slit function.…”

Section: Resultsmentioning

confidence: 99%

Focusing of a neutral helium beam below one micron

et al. 2012

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In 2008 we presented the first images obtained with a new type of matter wave microscope: NEutral Helium Atom MIcroscopy (NEMI). The main features in NEMI are the low energy of the atoms (<0.1 eV) and the fact that they are neutral. This means that fragile and/or insulating samples can be imaged without surface damage and charging effects. The ultimate resolution limit is given by the de Broglie wavelength (about 0.06 nm for a room-temperature beam), but reaching a small focus spot is still a major challenge. The best result previously was about 2 µm. The main result of this paper is the focusing of a helium atom beam to a diameter below 1 µm. A particular challenge for neutral helium microscopy is the optical element for focusing. The most promising option is to manipulate neutral helium via its de Broglie wavelength, which requires optical elements structured to nanometre precision. Here we present an investigation of the helium focusing properties of nanostructured Fresnel zone-plates. Experiments were performed by varying the illuminated area and measuring the corresponding focused spot sizes and focused beam intensities. The results were fitted to a theoretical model. There is a deviation in the efficiency of the larger zone plate, which indicates a distortion in the zone-plate pattern, but nevertheless there is good agreement between model and experiments for the focus size. This together with the demonstration of focusing to below 1 µm is an important step towards nanometre resolution neutral helium microscopy.

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“…For the experim ent presented here, the velocity spread o f the helium beam was the lim iting factor for the focused spot size. A higher speed ratio (m onochrom aticity) o f the helium beam can be obtained in various w ays [26][27][28] so that better focusing should be possible in the future. For the highest resolutions, velocity selection o f the beam will be necessary, w hich will reduce the focused beam intensity.…”

Section: Discussionmentioning

confidence: 99%

Focusing of a neutral helium beam with a photon-sieve structure

et al. 2015

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The manipulation of low-energy beams of neutral atoms and molecules via their de Broglie wavelength is a branch of atom optics often referred to as de Broglie matter wave optics. The application areas include fundamental quantum mechanics, atom interferometry, and the development of new microscopy instrumentation. The focusing of de Broglie matter waves with a Fresnel zone plate was used to demonstrate the first neutral helium microscopy imaging. The ultimate resolution of such a microscope is limited by the width of the outermost zone. Because a Fresnel zone plate for atoms cannot be fabricated on a substrate (the low-energy atom beams would not be able to penetrate the substrate material), this gives a fabrication determined limit for the first-order focus of around 30-50 nm. Therefore, it is important to search for alternative optical elements that enable higher resolution. Photon sieves consist of a large number of pinholes, arranged suitably relative to the Fresnel zones. The great advantages are that the width of the pinholes can be larger than the respective Fresnel zones and a free-standing pinhole is much easier to fabricate than a free-standing zone. Thus, with a photon-sieve structure applied for de Broglie matter wave manipulation, the fabrication limit for focusing is reduced to potentially around 3-5 nm. Here we present a realization of such an "atom sieve," which we fabricated out of a silicon nitride (SiN) membrane, using electron-beam lithography and reactive ion etching. Our atom sieve is 178 p m in diameter and has 31 991 holes. The diameter of the holes varies from 1840 to 150 nm. Using abeam of neutral, ground-state helium atoms with an average wavelength of 0.055 nm, we demonstrate helium atom focusing down to a spot size of less than 4 pm . The focus size is limited by the intrinsic velocity spread of the helium beam.

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Neutral atom and molecule focusing using a Fresnel zone plate

Cited by 23 publications

References 25 publications

Helium reflectivity and Debye temperature of graphene grown epitaxially on Ru(0001)

Helium reflectivity and Debye temperature of graphene grown epitaxially on Ru(0001)

Focusing of a neutral helium beam below one micron

Focusing of a neutral helium beam with a photon-sieve structure

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