Transmission Electron Microscopy (TEM) 1.2.4 In Transmission Electron Microscopy (TEM)a thin solid specimen (s 200 nm thick)isbombarded in vacmwithahighly-focused,monoeeretic beam of propagat ugh the spe en.Aseries th en magni transmitted ele al.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 images from small regions of sample that con- tain contrast.due to several scattering mechanisms associated with interactions ctrons and the a i nts of the sa ple.Analysis of tr aeospanhcng electron images yields in ormation both about atom structure and abou Range of elements TEM does not specifically identify elements measured Destructive Yes,during specimen preparation Chemical bonding Sometimes,indirectly from diffraction and image information simulation Quantification Yes,atomic structures by diffraction;defect character- ization by systematic image analysis Accuracy Lattice parameters to four significant figures using convergent beam diffraction Detection limits One monolayer for relatively high-Zmaterials Depth resolution None,except there are techniques that measure sample thickness Lateral resolution Better than 0.2 nm on some instruments Imaging/mapping Yes Sample requirements Solid c 】coate inst ators. Typically Main uses Atomic struct and Microstructural analysis of solid materials,providing high lateral resolution Instrument cost $300,000-$1,500,000 Size 100 ft.2 to a major lab 10 INTRODUCTION AND SUMMARIES Chapter 1
Transmission Electron Microscopy (TEM) 1.2.4 In Transmission Electron Microscopy (TEM) a thin solid specimen (5 200 nm thick) is bombarded in vacuum with a highly-focused, monoenergetic beam of electrons. The beam is of sufficient energy to propagate through the specimen. A series of electromagnetic lenses then 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 images from small regions of sample that contain contrast, due to several scattering mechanisms associated with interactions between electrons and the atomic constituents of the sample. Analysis of transmitted electron images yields information both about atomic structure and about defects present in the material. Range of elements Destructive Chemical bonding information Quantification Accuracy Detection limits Depth resolution Lateral resolution Imaging/mapping TEM does not specifically identify elements measured Yes, during specimen preparation Sometimes, indirectly from diffraction and image simulation Yes, atomic structures by diffraction; defect characterization by systematic image analysis Lattice parameters to four significant figures using convergent beam diffraction One monolayer for relatively high-Zmaterials None, except there are techniques that measure sample thickness Better than 0.2 nm on some instruments Yes Sample requirements Solid conductors and coated insulators. Typically 3-mm diameter, c 200-nm thick in the center Main uses Atomic structure and Microstructural analysis of solid materials, providing high lateral resolution Instrument cost $300,000-$1,500,000 Size 100 fL2 to a major lab 10 INTRODUCTION AND SUMMARIES Chapter 1
Energy-Dispersive X-Ray Spectroscopy(EDS) 1.3.1 When the atoms in a material are ionized by a high-energy radiation they emit char- acteristic X rays.EDS is an acronym describing a technique of X-ray spectroscopy that is based on the collection a nd en EDS syste m consists of a source of high -energy ra adia ple;a solid state de etector,usually made from lithium-drifted silicon,Si(Li);and signal processing electronics.EDS spectrometers are most frequently attached to electron column instruments.X rays that enter the Si(Li)detector are converted into signals which can be processed by the electronics into an X-ray energy histo- This X-ray spectrum onsists of a series ks rep of the unt of each ment in the sample.The numb nts in eac peak may be further converted in o elemental weight concentration either by com- parison with standards or by standardless calculations. Range of elements Boron to uranium Destructive No Chemical bonding Not readily available information Quantification Best with standards,although standardless methods are widely used Accuracy Nominally 4-5%,relative,for concentrations >5%wt. Detection limits 100-200 ppm for isolated peaks in elements with Z>11,1-2%wt.for low-Zand overlapped peaks Lateral resolution .5-1 um for bulk samples;as small as 1 nm for thin samples in STEM Depth sampled 0.02 to um,depending on Z and keV Imaging/mapping In SEM,EPMA,and STEM Sample requirements Solids,powders,and composites;size limited only by the stage in SEM EPMA and XRF;liguids in XRF: 3 mm diameter thin foils in TEM Main usc Cos 0.00 depending(no including the clectron microscope) 11
Energy-Dispersive X-Ray Spectroscopy (EDS) 1.3.1 When the atoms in a material are ionized by a high-energy radiation they emit characteristic X rays. EDS is an acronym describing a technique of X-ray spectroscopy that is based on the collection and energy dispersion of characteristic X rays. An EDS system consists of a source of high-energy radiation, usually electrons; a sample; a solid state detector, usually made from lithium-drifted silicon, Si (Li); and signal processing electronics. EDS spectrometers are most frequently attached to electron column instruments. X rays that enter the Si (Li) detector are converted into signals which can be processed by the electronics into an X-ray energy histogram. This X-ray spectrum consists of a series of peaks representative of the type and relative amount of each element in the sample. The number of counts in each peak may be further converted into elemental weight concentration either by comparison with standards or by standardless calculations. Range of elements Destructive Chemical bonding information Quantification Detection limits Lateral resolution Depth sampled Imaging/mapping Boron to uranium No Not readily available Best with standards, although standardless methods are widely used Nominally P5%, relative, for concentrations > 5yo wt. 100-200 ppm for isolated peaks in elements with Z> 11,1-2% wt. for low-Zand overlapped peaks -5-1 pm for bulk samples; as small as 1 nm for thin samples in STEM 0.02 to pm, depending on Z and keV In SEM, EPMA, and STEM Sample requirements Solids, powders, and composites; size limited only by the stage in SEM, EPMA and XRF; liquids in XRF; 3 mm diameter thin foils in TEM To add analytical capability to SEM, EPMA and TEM $25,000-$100,000, depending on accessories (not including the electron microscope) Main use cost 11
Electron Energy-Loss Spectroscopy in the Transmission Electron Microscope(EELS) 1.3.2 In Electron Energy-Loss Spectroscopy (EELS)a nearly mo onochromatic beam of electrons is directed through an ultrathin specimen,usually in a Transmission (TEM)or Scanning Transmission(STEM)Electron Microscope.As the electron beam propagates through the specimen,it experiences both elastic and inelastic cies in the zed volume caus ange in the energy ent beam;the changes are analyzed by means of a spectrometer and counted by a suitable detector system.The intensity of the measured signal can be used to determine quantitatively the local specimen concentration,the elec- tronic and chemical structure,and the nearest neighbor atomic spacings. Range of elements Lithium to uranium;hydrogen and helium are some times possible Destructive o Chemical bonding Yes,in the near-edge structure of edge profiles information information Depth profiling Nonc,the specimen is already thin capabilities Quantification Without standards-+10-20%at.;with standards -1-2%at Detection limits -10-21g Depth probed Thickness of specimen(s2000 A) Lateral resolution r of the inci- pro e specimen Imaging capabilities Yes Sample requirements Solids;s ecimens must be transparent to electrons and -100-2000 A thick Main use Light element spectroscopy for concentration electronic,and chemical structure analysis at ultra- high lateral resolution in a TEM or STEM Cost As an accessory to a TEM or STEM:$50,000- $150,000(does not include electron microscope cost) INTRODUCTION AND SUMMARIES Chapter 1
Electron Energy-Loss Spectroscopy in the Transmission Electron Microscope (EELS) 1.3.2 In Electron Energy-Loss Spectroscopy (EELS) a nearly monochromatic beam of electrons is directed through an ultrathin specimen, usually in a Transmission (TEM) or Scanning Transmission (STEM) Electron Microscope. As the electron beam propagates through the specimen, it experiences both elastic and inelastic scattering with the constituent atoms, which modifies its energy distribution. Each atomic species in the analyzed volume causes a characteristic change in the energy of the incident beam; the changes are analyzed by means of a electron spectrometer and counted by a suitable detector system. The intensity of the measured signal can be used to determine quantitatively the local specimen concentration, the electronic and chemical structure, and the nearest neighbor atomic spacings. Range of elements Destructive Chemical bonding information Depth profiling Quantification Detection limits Depth probed Lateral resolution Imaging Capabilities Lithium to uranium; hydrogen and helium are sometimes possible No Yes, in the near-edge structure of edge profiles information None, the specimen is already thin capabilities Without standards +fl0-20% at.; with standards - 1-2% at. -lo-21 g Thickness of specimen (I 2000 A) 1 nm-10 pm, depending on the diameter of the incident electron probe and the thickness of the specimen Yes Sample requirements Solids; specimens must be transparent to electrons and - 100-2000 a thick Main use Light element spectroscopy for concentration, electronic, and chemical structure andysis at ultrahigh lateral resolution in a TEM or STEM As an accessory to a TEM or STEM: $50,000- $1 50,000 (does not include electron microscope cost) cost 12 INTRODUCTION AND SUMMARIES Chapter 1
Cathodoluminescence(CL) 1.3.3 In Cathodoluminescence (CL)analysis,electron-beam bombardment of a solid placed in vacuum causes emission of photons (in the ultraviolet,visible,and near- infrared range)due to ther s generated by the cident energetic ectrons.The signal provides a means for CL microscopy(i.e. CL images are displayed on a CRT)and spectroscopy (i.e.,luminescence spectra from selected areas of the sample are obtained)analysis of luminescent materials using electron probe instruments.CL microscopy can be used for uniformity char- acterization (e.g.,mapp segregation studies),whereas CLspectroscopy pro Range of elements Not element specific Sometimes Nondestructive Yes;c -in cert tain cases electron bombardment Detection limits Depth profiling Yes,by varying the range of electron penetra depd o the cleco bm ener (0k. ween 10 nm and sever hich Lateral resolution On the order of 1 um;down to about 0.1 um in special cases Imaging/mapping Yes Sample requirements Solid,vacuum compatible Quantification Difficult,standards needed Main use puritiesind2gaaiend。 Nondestr ects,and nescent material Instrument cos $25,000-$250,000 Size Small add-on item to SEM,TEM
Cathodoluminescence (CL) 1.3.3 In Cathodoluminescence (CL) analysis, electron-beam bombardment of a solid placed in vacuum causes emission of photons (in the ultraviolet, visible, and nearinfrared ranges) due to the recombination of electron-hole pairs generated by the incident energetic electrons. The signal provides a means for CL microscopy (i.e., CL images are displayed on a CRT) and spectroscopy (i.e., luminescence spectra from selected areas of the sample are obtained) analysis of luminescent materials using electron probe instruments. CL microscopy can be used for uniformity characterization (e.g., mapping of defects and impurity segregation studies), whereas CL spectroscopy provides information on various electronic properties of materials. Range of elements Chemical bonding information Nondestructive Detection limits Depth profding Lateral resolution Imaging/mapping Not element specific Sometimes Yes; caution-in certain cases electron bombardment may ionize or create defects In favorable cases, dopant concentrations down to 1014 atoms/cm3 Yes, by varying the range of electron penetration (between about 10 nm and several pm), which depends on the electron-beam energy (I40 kev). On the order of 1 pm; down to about 0.1 pm in special cases Yes Sample requirements Solid, vacuum compatible Quantification Difficult, standards needed Main use Nondestructive qualitative and quantitative analysis of impurities and defects, and their distributions in luminescent materials Instrument cost $25,000-$250,000 Size Small add-on item to SEM, TEM 13
Scanning Transmission Electron Microscopy (STEM) 1.3.4 In Scanning Transmission Electron Microscopy (STEM)a solid specimen,5- 500 nm thick,is bombarded in vacuum by a beam (0.3-50 nm in diameter)of trons.STEM i s are formed by and collecr aning this beam in ter across om pared to the TEM an advantage of the STEM is that many signals may be collected simultaneously:bright-and dark-field images;Convergent Beam Electron Diffrac- tion (CBED)patterns for structure analysis;and energy-dispersive X-Ray Spec- trometry (EDS)and Electron Energy-Loss Spectro etry(EELS)signals for ositional analy sis Taken these ana s techni s are re ermed Ana. out 100 times be ofioAWhen Mi ter spa angles are collected,extremely high-resolution images of atomic planes and even individual heavy atoms may be obtained. Range of elements Lithium to uranium Destructive Yes,during specimen preparation Chemical bonding Sometimes,from EELS information Quantification positional analysis from EDS or EELS,and crystal structure analysis from CBED Accuracy 5-10%relative for EDS and EELS Detection limits 0.1-3.0%wt.for EDS and EELS Lateral resolution Imaging,0.2-10 nm;EELS,0.5-10 nm;EDS,3-30 nm Yes,lateral resolution down to <5 nm Sample requirements Solid conductors and coated insulators typically 3 mm in diameter and <200 nm thick at the analysis point for imaging and EDS,but 50 nm thick for EELS Main uses nal anal ysis;high spatial resolution with good elen etection and accuracy;unique structural analysis with CBED Instrument cost $500,000-$2,000,000 Size 3m×4m×3m 14 INTRODUCTION AND SUMMARIES Chapter 1
Scanning Transmission Electron Microscopy (STEM) 1.3.4 In Scanning Transmission Electron Microscopy (STEM) a solid specimen, 5- 500 nm thick, is bombarded in vacuum by a beam (0.3-50 nm in diameter) of monoenergetic electrons. STEM images are formed by scanning this beam in a raster across the specimen and collecting the transmitted or scattered electrons. Compared to the TEM an advantage of the STEM is that many signals may be collected simultaneously: bright- and dark-field images; Convergent Beam Electron Diffraction (CBED) patterns fbr structure analysis; and energy-dispersive X-Ray Spectrometry (EDS) and Electron Energy-Loss Spectrometry (EELS) signals for compositional analysis. Taken together, these analysis techniques are termed Analytical Electron Microscopy (AEM). STEM provides about 100 times better spatial resolution of analysis than conventional TEM. When electrons scattered into high angles are collected, extremely high-resolution images of atomic planes and even individual heavy atoms may be obtained. Range of elements Destructive Chemical bonding information Quantification Accuracy Detection limits Lateral resolution Imaging/mapping capabilities Lithium to uranium Yes, during specimen preparation Sometimes, from EELS Quantitative cornpositional analysis from EDS or EELS, and crystal structure analysis from CBED 5-10% relative for EDS and EELS 0.1-3.0% wt. for EDS and EELS Imaging, 0.2-10 nm; EELS, 0.5-10 nm; EDS, 3-30 nm Yes, lateral resolution down to < 5 nm Sample requirements Solid conductors and coated insulators typically 3 mm in diameter and c 200 nm thick at the analysis point br imaging and EDS, but < 50 nm thick for EELS Microstructural, crystallographic, and compositional analysis; high spatial resolution with @ elemental detection and accuracyj unique structural analysis with CBED Main uses Instrument cost $500,000-$2,000,000 Size 3mx4mx3m 14 INTRODUCTION AND SUMMARIES Chapter 1