STEMPack

A powerful way to carry out electron energy loss spectroscopy (EELS) is in conjunction with scanning transmission (STEM) mode on a high-performance analytical TEM instrument. By combining EELS and STEM, one can obtain high-quality spectral data from precisely targeted points within a scanned image or line profile. This approach is the basis of the technique known as STEM Spectrum Imaging (SI).

STEM Spectrum Imaging systematically probes a defined TEM specimen area to gather from it the maximum possible information in a fully automated data acquisition session. The resulting multi-dimensional data set (comprising at least the lateral x and y spatial dimensions plus the electron energy loss) can then be taken to an off-line analysis station for extraction of quantitative specimen information. Key benefits of the STEM SI technique include:

• Systematic and unbiased sampling of specimen properties
• Maximum analytical specimen information for a given dose
• Complete capture of all information, facilitating detection of unexpected minor constituents during post-processing
• Simultaneous collection of all elemental signals to yield multi-element maps from a single data acquisition session
• Detailed EELS data amenable to advanced quantification techniques that yield the most accurate elemental maps possible
• Best possible EELS energy resolution to enable advanced chemical mapping techniques based on fine structure analysis
• Rich, unbiased data ideally suited to powerful techniques like principle component and multivariate statistical analysis

STEM SI requires a transmission electron microscope with scanning unit, a digital STEM beam control and imaging system, a well-optimized annular dark field STEM detector, and an EELS spectrometer. In order to collect high-quality STEM SI data sets, all these components must operate in concert within an integrated software system for instrument control and data acquisition.

Gatan’s STEMPack system is a comprehensive package for advanced analytical STEM support for any TEM/STEM equipped with a Gatan EELS spectrometer (ENFINA or GIF) already operating under the Gatan Microscopy Suite software. Use it to carry out a range of STEM applications, from high-quality digital STEM imaging to full STEM SI with EELS. The package includes all needed hardware and software, as follows:

• Gatan’s DigiScan™, a digital beam control and digital STEM signal acquisition system
• A pneumatically-retractable BF/DF STEM detector, with an ADF collection-angle range well-suited to simultaneous EELS
• Electronics and cabling for interfacing the DigiScan™ and BF/DF detector to the microscope’s STEM system
• Gatan Microscopy Suite software licenses for basic digital STEM imaging as well as advanced STEM SI data acquisition, visualization, and analysis

With options listed below, one can upgrade the system to support simultaneous acquisition of several further STEM-mode signals, including:

• Additional analog STEM signals such as HAADF, SE, and BSE
• Processed pulses for single-electron or single-photon counting, as well as other applications like EDS window counting
• Energy-dispersive X-ray (EDS) spectra from selected EDS systems