Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM) and Aberration Corrected STEM (AC STEM)
Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), and Aberration‑Corrected STEM (AC‑STEM) are closely related techniques that image a sample using a high‑energy electron beam. Typical image resolutions are around 1–2 Å for TEM and STEM, with AC‑STEM achieving sub‑Å (≤1 Å) spatial resolution. High‑energy electrons (80–300 keV) are transmitted through electron‑transparent samples. These methods offer significantly better spatial resolution than SEM, but often require more complex sample preparation.
Though TEM, STEM, and AC‑STEM are more time‑intensive than many other commonly used analytical tools, a wide variety of signals are accessible, enabling chemical and structural analysis at the nanoscale. In addition to high image resolution, it is possible to characterize crystallographic phase, crystallographic orientation (using electron diffraction SAD, PED, NBD, Lattice Mapping), generate elemental maps (via EDS or EELS), and acquire images that highlight elemental contrast (Z‑contrast or HAADF‑STEM mode). With AC‑STEM, atomic‑column imaging and enhanced EDS and EELS resolution becomes routine. All of these capabilities can be applied to precise locations using Focused Ion Beam (FIB) sample preparation. TEM, STEM, and AC‑STEM are excellent failure analysis tools for thin films, advanced materials, and IC samples.
Ideal Uses
- Metrology at 0.2 nm resolution (sub‑0.1 nm with AC‑STEM)
- Identification of nm‑sized defects on integrated circuits, including embedded particles and via residues
- Determination of crystallographic phases at the nanometer scale
- Nanoparticle characterization: size, core/shell structure, agglomeration, annealing effects
- Catalyst studies, including single‑atom and atomic‑column imaging (AC‑STEM)
- Nanometer‑scale elemental maps (≤1 nm scale using AC‑STEM EELS/EDS)
- III‑V superlattice characterization
- Crystal defect characterization (dislocations, grain boundaries, voids, stacking faults)
Strengths
- Sub‑0.2 nm (2 Å) image resolution; sub‑Å imaging with AC‑STEM
- The highest spatial‑resolution elemental mapping of any analytical technique (EDS, EELS)
- Small‑area crystallographic information (TEM, PED, SAED, 4D)
- Strong contrast between crystalline and amorphous materials without chemical staining
- Z‑contrast HAADF imaging for composition and thickness mapping
- Enhanced analytical sensitivity and spatial precision using AC‑STEM
- Localized bonding/chemistry for some elements (EELS)
Limitations
- Significant sample preparation time
- Small sampling volumes; samples are typically ~100 nm thick and ~5 × 5 μm (even smaller for AC‑STEM work)
- Some materials are not stable under high‑energy electron beams
- AC‑STEM requires high stability and highly optimized sample conditions
Technical Specifications (TEM, STEM & AC-STEM)
- Signals Detected: Transmitted electrons, scattered electrons, secondary electrons, x‑rays
- Elements Detected: B-U (EDS, EELS)
- Detection Limits: 0.1-1 at%
- Imaging/Mapping: Yes (EDS, EELS)
- Ultimate Lateral Resolution:
- <0.2 nm (TEM/STEM); <0.1 nm with AC‑STEM
Would you like to learn more about using TEM and STEM?
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