title: Convenient contrast enhancement by a hole-free phase plate.
abstract: Decrease of the irradiation dose needed to obtain a desired signal-to-noise ratio can be achieved by Zernike phase-plate imaging. Here we present results on a hole-free phase plate (HFPP) design that uses the incident electron beam to define the center of the plate, thereby eliminating the need for high precision alignment and with advantages in terms of ease of fabrication. The Zernike-like phase shift is provided by a charge distribution induced by the primary beam, rather than by a hole in the film. Compared to bright-field Fresnel-mode imaging, the hole-free phase plate (HFPP) results in two- to four-fold increase in contrast, leading to a corresponding decrease in the irradiation dose required to obtain a desired signal-to-noise ratio. A local potential distribution, developed due to electron beam-induced secondary-electron emission, is the most likely mechanism responsible for the contrast-transfer properties of the HFPP.
authors: National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6G2M9. mmalac@ualberta.ca
authors: Marek
authors: M
authors: Malac
authors: Marco
authors: M
authors: Beleggia
authors: Masahiro
authors: M
authors: Kawasaki
authors: Peng
authors: P
authors: Li
authors: Ray F
authors: RF
authors: Egerton
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D004867:Equipment Design / Q000295:instrumentation* / Q000379:methods*; D046529:Microscopy, Electron, Transmission / Q000379:methods*; D008858:Microscopy, Phase-Contrast; D059629:Signal-To-Noise Ratio