Improving SEM Imaging Performance Using Beam Deceleration

Phifer, D.; Tuma, L.; Vystavel, T.; Wandrol, Petr; Young, Richard

doi:10.1017/s1551929509000170

Cited by 36 publications

(18 citation statements)

References 2 publications

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“…Furthermore, the energy spread of the electron gun increases at low beam energies, resulting in degradation of the electron-optical performance due to higher chromatic aberration. This can however be mitigated using beam deceleration techniques whereby the source emits at a high voltage but a negative bias is applied to the sample to reduce the landing voltage (Phifer et al, 2009). Low-voltage SEM imaging is also more susceptible to hydrocarbon contamination (Postek, 2006).…”

Section: Introductionmentioning

confidence: 99%

Helium ion microscopy of Lepidoptera scales

Boden¹,

Asadollahbaik²,

Rutt³

et al. 2011

Scanning

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In this report, helium ion microscopy (HIM) is used to study the micro and nano-structures responsible for structural color in the wings of two species of Lepidotera from the Papilionidae family: Papilio ulysses (Blue Mountain Butterfly) and Parides sesostris (Emerald-patched Cattleheart). Electronic charging under the beam of uncoated scales from the wings of these butterflies is successfully neutralized, leading to images displaying a large depth-offield and a high level of surface detail, which would normally be obscured by traditional coating methods used for scanning electron microscopy (SEM). The images are compared to those from variable pressure SEM, demonstrating the superiority of HIM at high magnifications. In addition, the large depth-of-field capabilities of HIM are exploited through the creation of stereo pairs which allows the exploration of the third dimension. Furthermore, the extraction of quantitative height information which matches well with cross-sectional transmission electron microscopy (TEM) measurements from the literature is demonstrated.

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Section: Introductionmentioning

confidence: 99%

Helium ion microscopy of Lepidoptera scales

Boden¹,

Asadollahbaik²,

Rutt³

et al. 2011

Scanning

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“…Applying a negative potential to the sample reduces the landing energy. This improves the BSE signal via several mechanisms (Paden & Nixon, ; Frank & Müllerová, ; Phifer et al ., ). First, the decelerating field accelerates the BSEs in the direction normal to the surface, thereby focusing them into a smaller solid angle, which means BSEs that otherwise would not strike the detector now contribute to the signal.…”

Section: Resultsmentioning

confidence: 97%

Automated in‐chamber specimen coating for serial block‐face electron microscopy

Titze

Denk

2013

Journal of Microscopy

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SummaryWhen imaging insulating specimens in a scanning electron microscope, negative charge accumulates locally ('sample charging'). The resulting electric fields distort signal amplitude, focus and image geometry, which can be avoided by coating the specimen with a conductive film prior to introducing it into the microscope chamber. This, however, is incompatible with serial block-face electron microscopy (SBEM), where imaging and surface removal cycles (by diamond knife or focused ion beam) alternate, with the sample remaining in place. Here we show that coating the sample after each cutting cycle with a 1-2 nm metallic film, using an electron beam evaporator that is integrated into the microscope chamber, eliminates charging effects for both backscattered (BSE) and secondary electron (SE) imaging. The reduction in signalto-noise ratio (SNR) caused by the film is smaller than that caused by the widely used low-vacuum method. Sample surfaces as large as 12 mm across were coated and imaged without charging effects at beam currents as high as 25 nA. The coatings also enabled the use of beam deceleration for non-conducting samples, leading to substantial SNR gains for BSE contrast. We modified and automated the evaporator to enable the acquisition of SBEM stacks, and demonstrated the acquisition of stacks of over 1000 successive cut/coat/image cycles and of stacks using beam deceleration or SE contrast.

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“…Beam deceleration by applying a negative bias to the sample, thereby reducing the landing energy, has been implemented in several commercial SEMs to improve imaging resolution and reduce sample damage. 9 In this paper, a positive bias is applied to the sample ( Fig. 1) to achieve higher landing energies, thereby generating higher energy x-rays for EDS applications on the low-voltage FESEM.…”

Section: Theory and Operation A Sample Biasingmentioning

confidence: 99%

High-voltage energy dispersive x-ray spectrometry using a low-energy primary beam

Klyachko

Davilla

et al. 2014

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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This paper proposes a way to do energy dispersive x-ray spectroscopy (EDS) at high accelerating voltages using a low-voltage field emission scanning electron microscope (FESEM). By biasing the sample to a positive voltage, the electron landing energy (also known as the x-ray excitation energy) is increased, effectively extending the EDS capabilities of the low-voltage SEM. This positive biasing reduces the signal-to-noise ratio of the FESEM image, but it also introduces scaling and offset errors. A one-time calibration procedure is shown to compensate for these distortions allowing the user to view the unbiased image, and then do a precise superposition of the low energy image, high energy image, and EDS elemental map. The proposed solution is implemented on a commercial low-voltage FESEM with an EDS energy resolution of 130 eV.

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Improving SEM Imaging Performance Using Beam Deceleration

Cited by 36 publications

References 2 publications

Helium ion microscopy of Lepidoptera scales

Helium ion microscopy of Lepidoptera scales

Automated in‐chamber specimen coating for serial block‐face electron microscopy

High-voltage energy dispersive x-ray spectrometry using a low-energy primary beam

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