T. E. MIn Transmission Electron Microscopy ( TEM ) a thin solid specimen ( 5 200 nm thick ) is bombarded in vacuumwith a highly - focused, monoenergeticbeam of elec - trons. The beam is of sufficientenergyto propagate through the specimen. Aseries of electromagneticlensesthen magnifies this transmitted electron signal. Diffracted electrons are observed in the form of a diffraction pattern beneath the specimen. This information is used to determine the atomic structure of the material in the sample. Transmitted electrons form imagesfrom small regions of samplethat con - tain contrast, due to several scattering mechanisms associated with interactions between electronsand the atomic constituents of the sample. Analysis of transmit - ted electron images yields information both about atomic structure and about defectspresent in the material.
... [مشاهده متن کامل]
Range of elements
Destructive
Chemicalbonding information
Quantification
Accuracy
Detection limits Depth resolution
Lateral resolution Imaging/mapping
TEM does not specificallyidentifyelements measured
Yes, during specimen preparation
Sometimes, indirectlyfrom diffractionand image simulation
Yes, atomic structures by diffraction; defect character - ization by systematicimage analysis
Lattice parameters to four significant figures using convergentbeam diffraction
One monolayer for relativelyhigh - Zmaterials
None, except there are techniques that measure sample thickness
Better than 0. 2 nm on some instruments Yes
Samplerequirements Solid conductors and coated insulators. Typically 3 - mm diameter, c 200 - nm thick in the center
Main uses Atomic structure and Microstructural analysisof solid materials, providing high lateral resolution
Instrument cost $300, 000 - $1, 500, 000 Size 100 fL2 to a major lab
. . .
@1939
Ruska @1986
