上海交通大学：《Structural and Chemical Characterization of Materi》教学资源_SEM1_Scanning electron microscopy

Yirtual Source First Condenser Lens Condenser Aperture Second Condenser Lens Objective Aperture ☒☒ Scan Coils Objective Lens Scanning electron microscopy Sample Lanting Zhang School of Materials Science and Engineering. SJTU lantingzh@sjtu.edu.cn 1

Scanning electron microscopy Lanting Zhang School of Materials Science and Engineering, SJTU lantingzh@sjtu.edu.cn 1

LM Lamp TEM Electrons Similarity "lllumination" between OM and Glass lens Electromagnetic lens TEM Condenser lens Specimen Glass lens Electromagnetic lens Objective lens First image Glass lens Projector lens Electromagnetic lens Final image Ocular Fluorescent screen Eye 2

Similarity between OM and TEM 2

Confocal scanning microscopy aser 5ca纳ni9 mi个t0r5 detector pin hole microscope Pinhole aperture sample lnle一+

Confocal scanning microscopy 3

General idea of scanning electron microscope (SEM) Source of illumination Light Scanning microscope electron (LM) microscope Condenser lens (SEM) Focusing lens Objective lens Specimen Projection lens Electron detector Eye Stage 4

General idea of scanning electron microscope (SEM) 4

Image generation in SEM:raster scan Acceleration voltage Cathode Wehnelt cylinder Anode This is very much similar to TV Condensor lens 1 FASTX Screen:Brightness is proportional to Condensor lens 2 START SE or BSE signal SLOW 图 Scan generator Deflection coils END (X and Y (scan) deflection) Objective ens Amplifiers ←BSE detector SE detector Secondary Back-scattered electrons(SE electrons Probe (BSE) 5

Image generation in SEM: raster scan 5 This is very much similar to TV

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 electron￾specimen 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