Images are pretty, but spectra can tell you just what is causing the luminescence. Identifying which peaks are caused by what activator, defect, band gap, or whatever is really physics. From my perspective, I can identify peaks only by reading what other people have written about them.
The whole system is designed for the spectrum range 185-2500 nm. However, the parts we have only cover the 185-1000 nm range, at most. In general, geological materials produce rather broad emission peaks, so the high-resolution gratings and narrow slit widths may not very useful for most samples. However, especially with lanthanide activators, it is probably a good idea to experiment. For semiconductors, peaks can be pretty narrow.
Go to: Acquisition / acquisition parameters.
Set the Range to whatever range you want, say 300-900 nm, and click the square to its right, so that it is light-blue.
Set the Accquisition time. 10 seconds is probably a good place to start, longer for dim things, shorter for bright things.
Set the Detector to Syncerity.
Set the Grating to 300, or another one if you have narrow peaks.
Set the Front entrance slit to 7000 microns (wide open). Narrow the slit later when you see what you have.
Set the Exit mirror to CCD.
Set the Filter wheel to None.
Go to the place you want to acquire the spectrum. Remember to focus only using the stage Z-axis control.
Zoom in to 1000-3000x. If your sample has stable luminescence, set the beam on the SEM to spot mode (SEM Scanning tab, Spot check box, spot must be in the center). If not, raster at a fast speed in Reduced mode over a small area. Reduced mode is turned on with the button over the magnification knob on the SEM keyboard. This mode reduces the electron beam power per unit area, decreasing fading effects.
Select the Spectra tab.
Press the Acquire spectrum button.
Spectrum acquisition should start. Its acquired in segments, a small number for the 300 lines/mm grating, more for the higher-resolution 1200 and 1800 lines/mm gratings (see below). The carousel can hold three gratings, which can be exchanged. Each acquisition segment takes the Acquisition time you set above, and each segment is displayed as it is finished. A timer in the lower-left of the screen tells you how much time is left. If you don’t like the spectrum, you can cancel it by pressing the Stop All button.
Use the graph controls, like the one indicated, which lets you change the Y-axis scale, to view the whole spectrum, or part of it.
You can acquire more than one spectrum in the graph window. To do something with one, select by clicking the colored squares. Then you can save or process the active spectrum. Be sure to save every spectrum you want to keep in the LabSpec format. Those can be reprocessed, other formats can’t. Spectra exported to text can be imported easily into spreadsheets.
For processing a selected spectrum, go to Menu Processing. You can play around with your spectrum to find out what types of processing work to pretty it up. Probably the most important is Despike, for noisy patterns.
