KENBIKYO Vol.50▶No.3 2015

Modern SEM Gives Rich Information
―Application of the State of the Art SEM to Steel Research―

Kaoru Sato

JFE Steel Corporation, Steel Research Laboratory

Abstract: This year marks the 50th anniversary of the first launch of a commercial scanning electron microscope. Thanks to the utilization of the field emission gun, SEM has achieved a high resolution and it is widely used today. Low voltage SEM has become common because of the development of various beam deceleration techniques. These techniques are particularly useful for materials characterization due to the small penetration depth of the primary beam.
Despite the usefulness of SEM, understanding SEM contrast is not straightforward: every SEM, even from the same manufacturer, gives different contrast when an identical specimen is observed. A change in both the accelerating voltage and the working distance results in a change in image contrast.
In this review, I will present examples of rich microstructural images obtained by using a state of the art SEM. Then, I will take up again the topic of signal detection in the SEM, which was a crucial issue in its early development.

Key words: scanning electron microscope, secondary electron, backscattered electron, contrast, signal acceptance