Topographic Imaging

Imaging the sample surface

Surfaces images of material, geo and life sience samples
Irene Heggstad. Sample courtesy: Nora Chiara Marek, Justas Zalieckas, Natacha Fabergas, and Jorun Egge.

Main content

Scanning electron microscopes are best known for images of the sample surface. The instruments at ELMILAB are equipped with several types of suitable detectors for this imaging mode allowing for the investigation of different surface characteristics. Everhart-Thornley detectors are the most versatile detectors and provide good signal/noise ratios for many samples, in-lens secondary electron detectors are most sensitive for features on the uppermost surface layer, while other detectors are optimized for imaging under low vacuum conditions.

For imaging in a high vacuum, samples must be dry and shall not release any gaseous substances. Rigid samples can be air-dried, but many fragile wet samples would suffer from phase-change-induced damages. Such samples can be processed at ELMILAB with freeze-drying, chemical, and critical point drying to prevent drying artifacts.

While conductive samples can be imaged without further treatment, non-conductive samples are prone to charge accumulation impairing the imaging process. ELMILAB offers sample coating with a wide range of conductive materials (Au/Pd, Ir, Pt, and C) to reduce charging effects on various types of samples.

If sample charging remains an issue or sample coating shall be prevented, all scanning electron microscopes available at ELMILAB offer the option to image the samples at low vacuum conditions. The floating gas molecules in the vicinity of the sample get ionized and effectively transport charges away from the sample. Specific detectors optimized for such image conditions can be used. Gassing and moist samples can also be imaged in this mode.