title: Maintaining the genuine structure of 2D materials and catalytic nanoparticles at atomic resolution.
abstract: The recent development of atomic resolution, low dose-rate electron microscopy allows investigating 2D materials as well as catalytic nano particles without compromising their structural integrity. For graphene and a variety of nanoparticle compositions, it is shown that a critical dose rate exists of <100 e(-)/Å(2) s at 80 keV of electron acceleration that allows maintaining the genuine object structures including their surfaces and edges even if particles are only 3 nm large or smaller. Moreover, it is demonstrated that electron beam-induced phonon excitation from outside the field of view contributes to a contrast degradation in recorded images. These degradation effects can be eliminated by delivering electrons onto the imaged area, only, by using a Nilsonian illumination scheme in combination with a suitable aperture at the electron gun/monochromator assembly.
authors.affiliation: Departamento de Física, ESFM-IPN, Ed. 9, UPALM-Zacatenco, México, D.F., Mexico. Electronic address: hcalder@esfm.ipn.mx.
authors.forename: H A
authors.initials: HA
authors.lastname: Calderon
authors.affiliation: National Center for Electron Microscopy and Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, One Cyclotron Rd, Berkeley, CA 94720, USA.
authors.forename: C
authors.initials: C
authors.lastname: Kisielowski
authors.affiliation: Dept. Mats. Sci. Eng., UCB, Berkeley, CA 94720, USA.
authors.forename: P
authors.initials: P
authors.lastname: Specht
authors.affiliation: National Center for Electron Microscopy and Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, One Cyclotron Rd, Berkeley, CA 94720, USA.
authors.forename: B
authors.initials: B
authors.lastname: Barton
authors.affiliation: Depto. Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, CINVESTAV-IPN, 07360 México, D.F., Mexico.
authors.forename: F
authors.initials: F
authors.lastname: Godinez-Salomon
authors.affiliation: Depto. Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, CINVESTAV-IPN, 07360 México, D.F., Mexico.
authors.forename: O
authors.initials: O
authors.lastname: Solorza-Feria
keywords: Atomic resolution; Beam damage; Beam induced transformation; Electron microscopy; Graphene; Low dose microscopy; Nanoparticles