SEM-EDX GUIDE FOR BUYERS

Chapter 2 - Magnification and Resolution

Magnification

Manufacturers often specify magnification as a quality indicator for the resolving power of their SEM instruments. Magnification is the ratio of the actual size of an object to its image. Thus, the numerical value depends on the size of the screen and is basically not unique.

Furthermore, the magnification does not say anything about the actual quality of imaging small structures. At a certain point, the ever finer scanning with the electron beam no longer provides any informative added value, since due to the limited resolution of the electron optics, no additional details can be visualized.

Real Resolution

Resolution is an objective measure and refers to the microscope's ability to image fine structures. For tabletop SEMs, the best resolution is around 10 nanometers.

The resolution is determined under standardized but impractical operating conditions. This gives the buyer a certain potential for disappointment, since the resolution given is barely achievable with real samples. After all, the resolution is a clear parameter that is suitable for comparing the imaging quality of different SEM instruments.

In practice, it is often more important to have a usable signal-to-noise ratio at the highest resolution in order to be able to image the desired structures in a meaningful way. For example, a CeB6 cathode delivers a tenfold higher electron density with the same spot size. This is advantageous for rapid and low-noise imaging as well as for X-ray elemental analysis.

Seeing Is Understanding

Let us demonstrate to you the resolution power, preferably with your own samples. The direct comparison gives you a good sense of the quality that can be achieved in practice.