Using SEM for Charge Cancellation on Non-Conductive Samples

The use of electron microscopes to observe biological specimens is frequently affected by issues of charging. Charging occurs when an electron beam is used on non-conductive materials, thus causing irradiation which leads to an accumulation of electrostatic charges on the specimen’s surface. This build-up of charges can make imaging and chemical analysis of the sample in question especially challenging.

High-Quality SEM Technology

In order to mitigate this common problem, simple methods can be used; for example, the application of a conductive layer on the surface of the sample, or imaging at higher pressures.

It is important to note however that the use of inappropriate coatings or low vacuum observation can decrease the resolution of the instrument, potentially hiding delicate structures and otherwise negatively affecting the electron microscope’s performance and analytical potential.

High quality SEM technology like that of the novel TESCAN S8000 Scanning Electron Microscope can help avoid common issues such as charging via its BrightBeam™ SEM column technology.

By using such as advanced technology it is possible to acquire crisp, clean and sharp images, even when observing non-conductive, charging samples. This advanced imaging can be obtained even without relying on low beam energies or the use of conductive coating.

TESCAN S8000 Scanning Electron Microscope

The TESCAN S8000’s design ensures that a high signal throughput can be achieved, even at very low beam energies. The addition of new filtering technology to an already powerful detection system means that charging can be reduced considerably.

The images below show how the TESCAN S8000 combines these exceptionally useful traits to examine the wall of a diatom cell.

Here, the shells have a highly complex morphology, including surfaces that are comprised of many nanopores.

Using traditional imaging techniques on a non-conductive biological sample like this would have previously been challenging due to the surface’s large charge accumulation, but the TESCAN S8000 with its BrightBeam™ column technology allows for acquisition of outstanding images without causing charging artifacts. It also offers higher spatial resolution, even on problematic samples such as diatoms.

A lateral overview of the diatom shell wall on the left and a detail on the right were acquired using accelerating voltage of 1 kV. The topographic contrast was achieved by using the E-T detector

Figure 1. A lateral overview of the diatom shell wall on the left and a detail on the right were acquired using accelerating voltage of 1 kV. The topographic contrast was achieved by using the E-T detector.

An overview of a diatom’s cell wall on the left and detail of the surface on the right image. The structures were imaged at 1 keV for enhanced surface sensitivity with the E-T detector

Figure 2. An overview of a diatom’s cell wall on the left and detail of the surface on the right image. The structures were imaged at 1 keV for enhanced surface sensitivity with the E-T detector.

This information has been sourced, reviewed and adapted from materials provided by TESCAN USA Inc.

For more information on this source, please visit TESCAN USA Inc.

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