History of SEM SEMs were developed after TEMs The first SEM image was obtained in 1935 by Max Knoll A British patent for an SEM was filed in 1937 by Manfred von Ardenne. The first commercial SEM was sold in 1965 by Cambridge Instruments Company (now Zeiss) 6
History of SEM • SEMs were developed after TEMs • The first SEM image was obtained in 1935 by Max Knoll • A British patent for an SEM was filed in 1937 by Manfred von Ardenne. • The first commercial SEM was sold in 1965 by Cambridge Instruments Company (now Zeiss) 6
Electron-specimen interactions Primary electron beam There are corresponding detectors to detect these signals. Backscattered electrons Characteristic X-rays Cathodoluminescence Secondary electrons Auger electrons Sample Absorbed electrons Transmitted electrons 7
Absorbed electrons Transmitted electrons Electron-specimen interactions 7 There are corresponding detectors to detect these signals
Monte Carlo simulation of electron- specimen interaction Sample surface 1μn marker Number of electrons 2000 Element 6,C Number backscattered 139 Atomic weight:12.01 10keV electrons Density:2.34 Backscattering Coefficient:6% 8
Sample surface Monte Carlo simulation of electronspecimen interaction 8
Back-Scattered Electrons (BSEs) The incident electrons from the primary beam elastically scattered back by the sample's atoms with very little energy loss (less than 1 eV). ⊙ IE BSE L K ⊙ 9
Back-Scattered Electrons (BSEs) • The incident electrons from the primary beam elastically scattered back by the sample's atoms with very little energy loss (less than 1 eV). 9
Secondary Electrons (SEs) Produced by inelastic interactions of high energy electrons with valence electrons of atoms in the specimen,causing the ejection of the electrons from the atoms. Pole piece Beam ⊙ SE III L23 L SE escape depth 10
Secondary Electrons (SEs) • Produced by inelastic interactions of high energy electrons with valence electrons of atoms in the specimen, causing the ejection of the electrons from the atoms. 10