File:U.S. Department of Energy - Science - 276 004 003 (16625683371).jpg

SCIENTIST STUDYING THE ATOMIC STRUCTURE AND CHEMISTRY OF HIGH-TEMPERATURE SUPERCONDUCTORS USING THE STEM.

THE SCANNING TRANSMISSION ELECTRON MICROSCOPE (STEM) DIFFERS FROM A CONVENTIONAL ELECTRON MICROSCOPE DUE TO ITS ABILITY TO MINIMIZE RADIATION DAMAGE. WITH A SCANNING TRANSMISSION ELECTRON MICROSCOPE, A SPECIMEN IS COOLED TO LIQUID NITROGEN TEMPERATURE AND SCANNED, RATHER THAN BEING IRRADIATED ALL AT ONCE. WHILE PASSING THROUGH THE SPECIMEN, SOME OF THE ELECTRONS INTERACT WITH IT, LOSING ENERGY TO WHATEVER THEY HIT OR CHANGING THEIR COURSE. DETECTORS COUNT EVERY TRANSMITTED ELECTRON, AND EACH ELECTRON CONTRIBUTES TO A FINAL PICTURE. AS A RESULT, FEWER ELECTRONS ARE NEEDED TO RECORD AN IMAGE THAN WITH OTHER ELECTRON MICROSCOPES, SO RADIATION DAMAGE TO THE SAMPLE IS MINIMIZED. THE PROCESS PERMITS SCIENTISTS TO SCRUTINIZE BIOLOGICAL SPECIMENS AT A RESOLUTION OF 2.5 ANGSTROMS. STEM CAN ALSO DETERMINE MOLECULAR WEIGHT AND MASS DISTRIBUTION WITHIN SINGLE MACROMOLECULES AND COMPLEXES.