Secondary electron imaging of atomic layers on silicon surfaces

Abstract

We earlier reported that the atomic steps on a Si(l11) clean surface can be clearly imaged by scanning electron microscopy (SEM) with a grazing incidence of the primary electron beam. In this paper, atomic step contrast is investigated with respect to the positional effects of the secondary electron (SE) detector. SE-images of the 1×2 and 2×1 domains on Si(100) are presented for the first time.An ultrahigh vacuum SEM equipped with a field emission electron gun (modified Hitachi S-800) is used for surface imaging. The pressure during SEM observation is about l×l0-8 Pa. The sample stage can be tilted from 0° (normal incidence) to 90° (grazing incidence). The SE-detector is placed on one side of the sample, near the tilt axis. The previous study utilized a long working distance of 35 - 40 mm between the objective lens and the sample. In the present study, the sample stage is modified so as to reduce the working distance down to 10 mm. This modification allows us to obtain higher resolution images.