TEM-EELS：Electron Energy-Loss Spectroscopy
Features
EELS spectrometry is a method of measuring the energy lost by the interaction of electrons with atoms as they pass through a thin sample. It is possible to identify the constituent elements and their electronic structures. Compared to energy dispersive X-ray (EDX) spectroscopy, EELS has the following advantages.
- Sensitivity of light elements is better.
- Higher energy resolution
- Higher spatial resolution, preventing detection of surrounding regions
- Chemical state analysis is possible (depending on the element).
Principle
EELS is a spectroscopic method that analyzes the binding energy state of an element by measuring the energy lost when an incident electron beam excites electrons in the sample.
EELS can broadly be divided into three regimes:
- Zero loss : Irradiating electrons without interaction with the sample and/or electrons subject to elastic scattering.
- Valence band excitation region : Plasmon and inter-band transitions corresponding to excitation energies of usually below 30eV. Yields bandgap and plasmon energies.
- Inner-shell electorn excitation (Core excitation) region : Used for compositional analysis because the energy loss depends uniquely on the electronic configuration of the element.
Application Examples
Compositional analysis and surface analysis of microscopically sized regions (0.2nm to 1μm).
- Qualitative analysis-of light and transition elements
- Chemical state analysis of elements
- Solid phase transitions of carbon
- Bond state analysis of compounds
- Dopant segregation analysis
- Li elemental distribution analysis
- TiNx composition analysis
Data examples
Fig. 4 shows the result of a point analysis of titanium oxide (TiOx).Crystalline TiOx films with a thickness of about 20 nm deposited on a Si substrate, were measured. The core-loss spectra acquired from the samples are consistent with the standard spectra of anatase, a TiO2 mineral. Crystal types can be identified because differences in electronic states cause differences in the shapes of the loss spectra corresponding to different bonds. The chemical state is determined by comparison with library data, reference samples, and theoretical calculations.
Specifications
Note: Since the integration time per point is shorter for elemental imaging using the 2,3-window method than for point analysis, the detection threshold is higher than that of point analysis. The 2- and 3-window methods map inner-shell transition energy losses with and without background subtraction, respectively.
Items for enquiries
- Purpose and content of measurement
- Observation purposes and regions of interest (ROI) and sample information
1. Number of samples, and availability of preliminary samples
2. Location of the point/area subject to analysis.
3. Handling instructions (for details see (S)TEM page)
- Details on delivery
1. Preferred due date for preliminary analysis report
2. Due date for delivery of final report
- Any other issues
Caution
- Like TEM, thinning of the sample by focused ion beam etching or milling is necessary. In some cases, however, thinning may prove difficult.
- Sample preparation and observation might alter the sample structure.
- Hydrocarbon and other substances from the sample preparation may adsorb to the system during analysis and, as a result, carbon and other elements may appear in the spectra.
［TEM-EELS］電子エネルギー損失分光法の分析事例はこちらからご覧ください。