Enviromental Scanning Electron Microscope (ESEM)
The Phillips/FEI XL30 Environmental Scanning Electron Microscope (ESEM) (installed Fall, 2001) is equipped with:
- an Oxford X-Max 50 mm2 Energy Dispersive Spectrometer (EDS),
- an Oxford Electron Backscatter Diffraction detector (EBSD) (installed in 2006),
- a Gatan PanaCL cathodoluminescence (CL) detector with RGB color filters for observation of near-true luminescent color,
- a suite of SE and BSE detectors (see ‘Imaging Capabilities’ below for details), and
- high- and low-(ESEM) vacuum modes.
What is an ESEM?
The primary function of the ESEM is to produce images of surface features at very high magnifications (100X to 100,000X) under variable states of vacuum (water pressure) in the specimen chamber. Samples (even wet ones) can be examined under conditions more similar to those in which the sample existed in nature (“environmental” conditions). Operated in ESEM mode it is possible to observe specimens in hydration states extending to 100%.
A Peltier cooled specimen stage is available and can operate between -5°C and +60°C. The primary application of this feature is to produce moisture on the sample.
A variety of BSE and SE detectors are available to use depending on the conditions in the specimen chamber.
- A Secondary Electron (SE) detector for imaging under high-vacuum.
- A Backscattered Electron (BSE) detector for imaging under high-vacuum.
- The Large Field Detector (LFD) can be used between 0.1 and 1.o Torr to detect BSE and SE signals at low accelerating voltage.
- The Gaseous Secondary Electron (GSED) detector allows SE detection at up to 20 Torr. The 500 µm aperture limits the magnification of this detector to~240x at a 7 mm working distance.
- The Wide Angle GSED allows SE imaging at up to 10 Torr. The ‘Wide Angle’ allows users to image samples at lower magnification compared to the GSED detector.
- The Standard Secondary Electron (ESD) detector contains a 500 µm aperture for imaging at up to 20 Torr and collects more SE signal compared to the GSED.
- The Standard/Wide Andle X-ray ESD has a working distance of 10 mm which is the same as the EDS detector, thus allowing users to simultaneously collect SE and X-ray signals at up to 10 Torr. The detector has a 1000 µm aperture allowing users to image at low magnification.
- The Gaseous BackScattered Electron (GBSD) detector allows BSE, SE, or BSE+SE imaging at up to 10 Torr using a 500 µm aperture. Like the GSED, the GBSD is limited to a minimum magnification of ~240x.
Oxford X-Max Energy Dispersive Spectrometer (EDS)
- The EDS detector can be used to analyze single spots, line transects, or large 2-D areas. The AzTec software allows users to collect data in multiple areas in an automated mode. Therefore, entire thin sections can be imaged (BSE/SE) and mapped.
Oxford Electron BackScattered Electron Detector (EBSD)
- The EBSD allows users to collect structural information for any sample that is stable under the electron beam. Because this detector can be used in low-vacuum, insulating samples can be analyzed. A pre-tilted stage is used to increase the fraction of electrons that are backscattered from the sample.
- The EBSD can be used to analyze single spots or large-2D areas. The AzTec software allows users to collect data from multiple areas in an automated mode.
Samples and Sample Preparation
The ESEM is mostly used to examine small rock chips, grain mounts, and polished thin sections. However, any material that is stable under the electron beam can be loaded into the instrument, for as long as the sample fits. The specimen chamber can accommodate a 50 mm (length/diameter) sample. Larger samples risk damaging a detector. The stage can accommodate seven 0.25″ SEM stubs, three 1″ SEM stubs, two standard-sized petrographic thin sections.
Requesting instrument time
All users should fill out the ‘Request to use the EPMA,ESEM,SEM‘ form. The purpose of the form is to communicate the goals of the project to the lab manager and lab assistant. The form also serves as an agreement between the user, advisor/account holder (if applicable), and the lab manager. Any questions regarding the form should be directed to the lab manager.
Internal (UT-Austin): $175/shift