title: Caustic imaging of gallium droplets using mirror electron microscopy.
abstract: We discuss a new interpretation of mirror electron microscopy (MEM) images, whereby electric field distortions caused by surface topography and/or potential variations are sufficiently large to create caustics in the image contrast. Using a ray-based trajectory method, we consider how a family of rays overlaps to create caustics in the vicinity of the imaging plane of the magnetic objective lens. Such image caustics contain useful information on the surface topography and/or potential, and can be directly related to surface features. Specifically we show how a through-focus series of MEM images can be used to extract the contact angle of a Ga droplet on a GaAs (001) surface.
authors.affiliation: School of Physics, Monash University, Victoria 3800, Australia.
authors.forename: S M
authors.initials: SM
authors.lastname: Kennedy
authors.forename: C X
authors.initials: CX
authors.lastname: Zheng
authors.forename: W X
authors.initials: WX
authors.lastname: Tang
authors.forename: D M
authors.initials: DM
authors.lastname: Paganin
authors.forename: D E
authors.initials: DE
authors.lastname: Jesson