Centres Científics i Tecnològics UB

Notícies

26.07.2018

Publicació de l'article “Quasi-parallel precession diffraction: Alignment method for scanning transmission electron microscopes.”

El Dr. Joaquim Portillo, responsable de la tecnologia de MET Aplicada a Materials dels CCiTUB, ha publicat l'article: “Quasi-parallel precession diffraction: Alignment method for scanning transmission electron microscopes” a la revista Ultramicroscopy. L'article s'ha dut a terme en col·laboració amb els investigadors següents: la Dra. Francesca Peiró, la Dra. Sònia Estradé i el Sr. Sergi Plana del departament d'Enginyeries de la Universitat de Barcelona, la Dra. Ute Kolb de la Johannes Gutenberg-Universität Mainz i el Dr. S.Nicolopoulos de l'empresa NanoMEGAS SPRL.

L'article és producte un cop més de la col·laboració Universitat-Empresa i, en aquest cas en concret, en el marc del conveni existent entre l'empresa NanoMEGAS SPRL i els CCiTUB.

El resum de l'article és el següent:

"A general method to set illuminating conditions for selectable beam convergence and probe size is presented in this work for Transmission Electron Microscopes (TEM) fitted with µs/pixel fast beam scanning control, (S)TEM, and an annular dark field detector. The case of interest of beam convergence and probe size, which enables diffraction pattern indexation, is then used as a starting point in this work to add 100Hz precession to the beam while imaging the specimen at a fast rate and keeping the projector system in diffraction mode. The described systematic alignment method for the adjustment of beam precession on the specimen plane while scanning at fast rates is mainly based on the sharpness of the precessed STEM image. The complete alignment method for parallel condition and precession, Quasi-Parallel PED-STEM, is presented in block diagram scheme, as it has been tested on a variety of instruments. The immediate application of this methodology is that it renders the TEM column ready for the acquisition of Precessed Electron Diffraction Tomographies (EDT) as well as for the acquisition of slow Precessed Scanning Nanometer Electron Diffraction (SNED). Examples of the quality of the Precessed Electron Diffraction (PED) patterns and PED-STEM alignment images are presented with corresponding probe sizes and convergence angles".

Per a més informació, poden accedir al següent link: [+].