Dedicated STEM for 200 to 40 keV operation^*

Nion Co., 1102 8th St., Kirkland, WA 98033, USA
www.nion.com

^a e-mail: krivanek.ondrej@gmail.com

Received: 23 October 2010
Revised: 28 February 2011
Accepted: 14 March 2011
Published online: 13 June 2011

Abstract

A dedicated STEM developed for operation at primary energies from 200 keV to 40 keV and lower is described. It has a new cold field emission gun (CFEG) that gives a normalized brightness of 3 × 10⁸ A/(m² sr V), and excellent short-term and long-term stability. It includes two gun lenses (one electrostatic and one electromagnetic), a fast electrostatic beam blanker, three condenser lenses, a corrector of third- and fifth-order geometric aberrations, an objective lens with low aberration coefficients, a flexible set of projector lenses, an ultra-stable sample stage, and provision for storing up to five samples under high vacuum and loading them into the microscope’s objective lens under remote control. The microscope is enclosed in a magnetically and acoustically shielding enclosure, which allows it to operate at a high performance level even in non-optimal environments. It has reached 53 pm resolution at 200 keV and 123 pm at 40 keV, and an EELS energy resolution of 0.26 eV.