Access:
The Department of Geosciences Electron Microprobe / SEM Facility is available to researchers both within the University of Massachusetts community as well as from other institutions worldwide. This includes use by faculty, staff and students. Interested individuals can be trained to use the instruments themselves or can obtain assisted services with the aid of an analyst. Sample preparation services are also available, including mounting, polishing and coating for conductivity.
The laboratories are maintained through a non-profit trust fund (UMass cost center), and revenues are derived via user fees based on an hourly rate schedule. Please contact Michael Jercinovic for information on the current fee schedule, and to arrange instruction and/or analytical services.
Anaytical and characterization services:
This analytical facility is primarily used for non-destructive, in-situ characterization of solid materials by electron microscopy. High magnification surface morphology is established by secondary electron imaging using scanning electron microscopy. Phase contrast imaging using backscattered electron detection is also available on all instruments, as is X-ray compositional mapping – typically done using polished specimens (some examples can be seen here).
Cathodoluminescence imaging is available in panchromatic mode on the Zeiss EVO 50 SEM and Cameca SX50 electron probe, and monochromatic spectral analysis is available on the SX50.
Quantitative compositional analysis is done by X-ray microanalysis via wavelength dispersive spectrometry (WDS) on the EPMA instruments, or by energy dispersive spectrometry (EDS, Zeiss SEM). The spatial resolution of analysis depends primarily on the required beam energy and properties of the specimen, but will typically be in the micron range for most solids. Quantitative analyses can be automated to allow acquisition of profiles (e.g. chemical gradients or interface studies). Sensitivity is also variable, but typical analysis is applied to major and minor elements (to 0.05 wt.%). In special cases, trace concentrations can be obtained (to the ppm level). Light elements are usually not analyzed directly (oxygen determination is generally done stoichiometrically), so typical analyses will include direct acquisition of elements of Z>8.
Samples should be flat and polished (typically to 1/4 micron or better), and should have a conductive carbon coat for quantitative analysis. For samples other than standard petrographic thin sections, 1-inch round polished pucks (less than 2cm thick) are easily mounted for EPMA. For samples with other dimensions, please contact us and we will see what we need to do to come up with a solution. The SEM can accommodate samples of various sizes and shapes, and typical Zeiss compatible pin-type mounts are of course standard. As mentioned above, sample preparation, including mounting, polishing and coating services are available.