TABLE OF CONTENTS Scanning electron microscopy with polarization analysis (SEMPA) has developed into a powerful technique to study domains in ultrathin films. In this chapter, we discuss from a very general point of view the instrumental aspects of the method. Examples of thin film investigations are given that demonstrate unique features of SEMPA. New solutions around apparent limitations of the technique are presented at the end, i.e., analyzing samples with contaminated surfaces and imaging in external fields.
In 1982, triggered by the investigations of the energy dependence of the spin-polarization of secondary electrons (SE), the idea emerged to use this effect in a microscope to image magnetic structures [1] , [2]. The combination of a conventional Scanning Electron Microscope (SEM) and a spin-polarization analyzer promised the potential of investigating magnetic microstructures with high spatial resolution. In 1984, the first spin-SEM was realized by Koike and coworkers [3], followed less than one year later by a microscope built at NIST [4]. The latter group introduced the abbreviation SEMPA, which stands for Scanning Electron Microscope with Polarization Analysis. We will use both acronyms interchangeably. The next instruments followed in Europe [5] , [6]. A sketch of SEMPA is given in Fig. 7.1. Due to the low depth of information, ultra-clean surfaces are essential, requiring ultrahigh vacuum (UHV) conditions. Since conventional SEMs usually do not operate in UHV, appropriate UHV-compatible columns (or guns) are rare and...
