Theoretical relation between spatial resolution and efficiency of detection in scanning hot electron microscope

To observe the spatial distribution of subsurface hot electrons (HEs) with a scanning probe, the relation between the spatial resolution and the hot e lectron current is investigated theoretically and the efficiency of HE dete ction is discussed. Using a sphere-plane model for the tip and the sample s urface in a scanning hot electron microscope (SHEM), the electrostatic pote ntial and the tunnel transmission are analyzed using the three-dimensional (3D) image charge method and quantum mechanical analysis, respectively, to simulate HE detection. The resolution and the hot electron current depend o n the hot electron energy and the tip-sample space and are related. The eff iciency of HE detection is defined and its dependence on the parameters is examined. For a given hot electron energy, the resolution is determined by the minimum hot electron current which is larger than the noise current.