High resolution scanning electron microscopy using field-emitted spin polarized electrons

Abstract

We present a simple “near field emission scanning electron microscope” (NFESEM) [1] capable of imaging conducting surfaces with high spatial resolution. In this instrument electrons are excited from the sample surface after undergoing interactions with a low-voltage (<60V) primary beam of electrons field-emitted from a tungsten tip positioned tens of nanometers above the sample. Topographic images, determined from the intensity variations of secondary and backscattered electrons, yield a vertical resolution on an atomic scale and a lateral resolution of less than two nanometers [2]. The topographic contrast of the extracted electrons and the field emission (FE) current are almost indistinguishable, in agreement with theoretical models of optimal spatial resolution [1]. Furthermore, the electron intensity images show more detail with higher resolution than FE current mapping (see Fig. 1). This implies that the secondary electron (SE) yield is more sensitive to additional parameters, which may be the local work function, specimen curvature, primary beam energy, and/or detector sensitivity [2]. We assert that additional analysis of these SEs will also exhibit a comparable resolution.