Introduction

Abstract

Through recent advances in ultrahigh resolution FE-SEM with novel electron optics and multidetection systems [1], where secondary electrons, high-angle backscattered electrons, and channeling backscattered electrons (BSE) are detected separately, the world of electron microscopy and practical surface analysis, which had been fairly static in the 1980s and 1990s, may be changed drastically. Thus, by reducing the accelerating voltage to about 1.0–2.0 kV and through selective detection of secondary electrons (SE), topographic details of both conductive and nonconductive surfaces are revealed at a lateral resolution of about 1.5 nm under uncoated conditions. Simultaneously and by selective detection of high-angle BSE, having compositional and channeling information, the lateral resolution of BSE images has also been improved dramatically, with an excellent atomic number contrast (Z-contrast) sensitivity; a lateral resolution comparable to, or even better than, that of in-lens SE imaging, i.e., ~1.5 nm, is often realized at an accelerating voltage of about 1.0–2.0 kV range. Further, electron channeling contrast imaging, through selective detection of channeling BSEs, i.e., the primary electrons that underwent Mott scattering, allows subgrains, fine precipitates of sizes down to several nanometers, or even dislocations to be imaged clearly and at high resolution in the bulk sample in SEM; the information of these kinds has been obtained previously by transmission electron microscopy of thin foil specimens prepared through slow and tedious sample preparation procedures.