ELECTON MICROSCOPY

THE BASICS

FIRST TRANSMISSION ELECTRON MICROSCOPE

1931- RUSTA AND KNOLL

ELECTRON MICROSCOPE

IS A VACCUUM

ELECTRONS BEHAVE LIKE LIGHT

ELECTRON HAS A NEGATIVE CHARGE THEREFORE ELECTRIC AND MAGNETIC FIELDS AFFECT ELECTRONS

ELECTRON GUN

FILAMENT: HEAT UP

CYLINDER: FOCUSES ELECTRONS

ANODE: ACCELERATED ELECTRONS

ELECTRON COLUMN

VACUUM SYSTEM

ELECTRON AND MAGNETIC LENSES

APPERTURES

SPECIMEN

IMAGE RECORDING

ELECTRON-SPECIMEN

ABSORPTION: SAME MATERIAL AND THICKNESS

ELECTRON SCATTERING: CREATE CONTRAST

REFLECTION (ELECTRON SCATTERING): REFLECTION OF MAIN ELECTRON BEAM – BACKSCATTERED ELECTRONS

EMISSION (INELASTIC SCATTERING): MAIN BEAM ELECTRONS TRANSFER ENERGY TO ORBITTING ELECRONS RESULTING IN EMISSION OF SECONDARY ELECTRONS. THIS LEADS TO PRODUCTION OF X-RAYS AND PHOTONS

DIFFRACTION: THIS TAKES PLACE IN CRYSTALLINE SAMPLES BECAUSE THEY CAUSE ELECTRON SCATTERING TO VARIOUS DIRECTIONS

PREPARING BIOLOGICAL SPECIMENS

FIXATION MAY BE REQUIRED TO PRESERVE THE STRUCTURE OF SPECIMEN

IT IS NOT NEEDED IN SMALL SAMPLES

FIXATION CAN BE CHEMICAL OR CRYO

SCANNING ELECTRON MICTOSCOPY

ELECTRON GUN

ANODE

MAGNETIC LENS

SCANNING COILS

BACKSCATTERED ELECTRON DETECTOR

SPECIMEN

SECONDARY ELECTRON DETECTOR

SCANNER