A New Low Energy Electron Microscope

Tromp, R. M.; Mankos, M.; Reuter, M. C.; Ellis, A W; Copel, M.

doi:10.1142/s0218625x98001523

Cited by 67 publications

(37 citation statements)

References 7 publications

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“…This is quite consistent with image resolution estimates made previously for LEEM (Bauer 1985) and what has been obtained experimentally (Tromp 2000). In LEEM, the aberration effects of the magnetic sector can be greatly reduced by focusing the image along its diagonal plane, making it essentially achromatic (Tromp et al 1998). The same principle applies to the current SPSSEM proposal.…”

Section: The Spectroscopic Scanning Electron Microscope Designsupporting

confidence: 90%

“…To obtain the corrected image shown in Figure 8c, the predeflection/postdeflection plates excitation strength was adjusted to 76 AT and the main sector plate's excitation strength was lowered to 21 AT. This ratio of 3.6 higher excitation strength on the predeflection/postdeflection plates with respect to the main sector plate in order to achieve double-stigmatic focusing is in general agreement with similar results reported in the context of LEEM experiments (Tromp et al 1998). Comparison between Figure 8b and c clearly shows that the method of using predeflection/postdeflection plates can compensate for the deflection distortions imposed by the magnetic sector plates.…”

Section: The Spectroscopic Scanning Electron Microscope Designsupporting

confidence: 89%

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A spectroscopic scanning electron microscope design

Khursheed

Osterberg

2004

Scanning

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Summary: This paper describes a proposal to improve the design of scanning electron microscopes (SEMs). The design is based upon using an SEM column similar to the conventional one, magnetic sector plates and a mixed field immersion objective lens. The optical axis of the SEM column lies in the horizontal direction and the primary beam is turned through 90 degrees before it reaches the specimen. This arrangement allows for the efficient collection, detection and spectral analysis of the scattered electrons on a hemispherical surface that is located well away from the rest of the SEM column. The proposed SEM design can also be easily extended to incorporate time multiplexed columns and multi-column arrays.

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Section: The Spectroscopic Scanning Electron Microscope Designsupporting

confidence: 90%

Section: The Spectroscopic Scanning Electron Microscope Designsupporting

confidence: 89%

A spectroscopic scanning electron microscope design

Khursheed

Osterberg

2004

Scanning

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“…A 200 nm aperture was used for the µ-LEED measurements, which allowed the determination of the orientation of the graphene grains on a grain-by-grain basis. Further details of this instrument are described in a previous publication 22 . The AFM measurements were performed in air using a Dimension Nanoscope III AFM in tapping mode.…”

Section: Methodsmentioning

confidence: 99%

Argon-assisted growth of epitaxial graphene on Cu(111)

et al. 2012

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The growth of graphene by catalytic decomposition of ethylene on Cu(111) in an ultra-high vacuum system was investigated with low energy electron diffraction, low energy electron microscopy, and atomic force microscopy. Attempts to form a graphene overlayer using ethylene at pressures as high as 10 mTorr and substrate temperatures as high as 900 • C resulted in almost no graphene growth. By using an argon overpressure, the growth of epitaxial graphene on Cu(111) was achieved.The suppression of graphene growth without the use of an argon overpressure is attributed to Cu sublimation at elevated temperatures. During the initial stages of growth, a random distribution of rounded graphene islands is observed. The predominant rotational orientation of the islands is within ±1 • of the Cu(111) substrate lattice.

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“…As a result, the interaction of low energy electrons (LEEs) with soft matter is not well understood. Here, we focus primarily on the interaction of low energy electrons with polymethylmethacrylate (PMMA) and related resist materials as used in extreme ultraviolet (EUV) lithography [1] to obtain a new understanding of key processes at low electron energies.In a low energy electron microscope [2] (LEEM) a sample is illuminated with electrons with adjustable 0-100 eV energy [3]. We use LEEM to expose thin PMMA films, monitoring changes both after and during exposure [4].…”

mentioning

confidence: 99%

Charge Catastrophe and Dielectric Breakdown During Exposure of Organic Thin Films to Low-Energy Electron Radiation

et al. 2017

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The effects of exposure to ionizing radiation are central in many areas of science and technology, including medicine and biology. Absorption of UV and soft-x-ray photons releases photoelectrons, followed by a cascade of lower energy secondary electrons with energies down to 0 eV. While these low energy electrons give rise to most chemical and physical changes, their interactions with soft materials are not well studied or understood. Here, we use a low energy electron microscope to expose thin organic resist films to electrons in the range 0-50 eV, and to analyze the energy distribution of electrons returned to the vacuum. We observe surface charging that depends strongly and nonlinearly on electron energy and electron beam current, abruptly switching sign during exposure. Charging can even be sufficiently severe to induce dielectric breakdown across the film. We provide a simple but comprehensive theoretical description of these phenomena, identifying the presence of a cusp catastrophe to explain the sudden switching phenomena seen in the experiments. Surprisingly, the films undergo changes at all incident electron energies, starting at ∼0 eV. DOI: 10.1103/PhysRevLett.119.266803 The interaction of ionizing radiation with matter is of vast scientific and technological (including biological and medical) importance. The interaction of UV and x-ray photons with matter is mediated by photoelectrons, as well as secondary electrons with a broad energy distribution that induce chemical changes in the material, be it a polymer, organic or inorganic hybrid, biological tissue, or even DNA. But these complex processes are hard to disentangle, as photon illumination sets the entire electron cascade in motion at once, without the possibility of discerning the role of electrons with different energies. As a result, the interaction of low energy electrons (LEEs) with soft matter is not well understood. Here, we focus primarily on the interaction of low energy electrons with polymethylmethacrylate (PMMA) and related resist materials as used in extreme ultraviolet (EUV) lithography [1] to obtain a new understanding of key processes at low electron energies.In a low energy electron microscope [2] (LEEM) a sample is illuminated with electrons with adjustable 0-100 eV energy [3]. We use LEEM to expose thin PMMA films, monitoring changes both after and during exposure [4]. The radiation chemistry of PMMA and related materials has been well studied, and there is consensus that irradiation causes scission of the main chains and removal of side groups [5][6][7][8][9][10]. Here, we identify key physical processes largely ignored in the literature: resist charging, exposure-induced changes in conductivity and secondary electron emission, and dielectric breakdown. We present a simple quantitative theory describing our data, identifying a cusp catastrophe [11] causing the instabilities seen during exposure. Even electrons with near-zero energy change the resist, suggestive of dissociative electron attachment processes [12] commonly neg...

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A New Low Energy Electron Microscope

Cited by 67 publications

References 7 publications

A spectroscopic scanning electron microscope design

A spectroscopic scanning electron microscope design

Argon-assisted growth of epitaxial graphene on Cu(111)

Charge Catastrophe and Dielectric Breakdown During Exposure of Organic Thin Films to Low-Energy Electron Radiation

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