eTraining Introduction

Specimen Preparation

Leica Ultracut UCT



Hitachi S-4700 FE-SEM

Hitachi FB-2000A FIB


Veeco Dim 3000 AFM

Fluorescence Microscopes



Why can't I touch the exchange rod?

By touching the sample rod you wipe off the grease from the exchange rod which results in the rod not moving smoothly and the grease getting on your fingers. Not only can it be transferred to your sample, but the grease is also toxic.

What should I do if the left computer monitor does not turn on?

Shut down all the software, logout and turn the computer off. Wait a few minutes and then turn it back on. Both monitors should be functioning then.

How do I move the cursor between screens?

If the MAG and MICRON bar are not visible on the LH CRT, then:

What type of samples can I view with the SEM?

Although there is a size limit which varies depending on the scope used and the type of sample, the largest sample would be around 1 ½ inches wide and ¾ inches tall. Biological samples must be dried in a certain way and then coated in gold, carbon, or an alloy in order to provide a pathway for the negatively charged electrons. The same must be done for any sample that is not conductive, since that is necessary for the electrons to be attracted to it and thus produce an image. Those are about the only restrictions to the sample.

What is the liquid nitrogen for?

It cools the EDS detector and reduces the thermally induced background or "leakage" current present in the signal.

What happens when I oversaturate the filament?

Oversaturating the tungsten filament will not increase the beam intensity; it merely shortens the filament life.

What happens if I do not saturate the filament enough?

If it is not fully saturated, then you will have failed to take advantage of available beam intensity. This results in a lower quality image due to a lower signal to noise ratio.

What should I do if the sample won't come off the exchange rod? The ball at the end just comes unscrewed and the sample is stuck on the rod.

When you attached the sample holder you twisted it on too tight. In the future, remember that you do not have to twist it on very tight, it just has to be a little snug. For now, contact lab personnel for help.

How do I sign up for time on the SEM?

Instrument calendars and instructions may be found under Reservations in the main ACMAL website. There is a Sign-Up Procedure posted.

How much time should I plan on signing up for?

This depends on the amount of work you plan to accomplish, but 1 or 2 hours is reasonable. Read the ACMAL Procedures and Policies for Electron Microscopy.

Do I have to take the class before using the SEM?

YES! This is a very expensive piece of equipment and we do not want you to break it. Users must be certified, otherwise an external operator is required. To become certified, users must take and pass the SEM course offered by the MSE department (MY4200/5200).

See Disclaimers under Support for more information.

What would be your recommendations for microanalysis conditions?

See also FAQs under Microanalysis for more general issues.

Aperture Choice

Choice of aperture depends on the results you wish to obtain. Use the smallest setting for imaging, and especially for long working distance situations. Larger apertures are necessary for X-ray analysis.

Beam Current

The condenser lens controls the beam current, and the larger the lens number, the smaller the current. Use a small current (large Condenser lens #: ~10-14) for high-resolution imaging, and a large current (small Condenser lens #: ~8-9 for EDS, and ~7-8 for WDS) for X-ray analysis.

Working Distance

The working distance must be 39 mm for X-ray analysis and large depth of field. It should be short (5 mm) for high-resolution imaging and for optimal BSE detection.

Coating Thickness

We can apply carbon or metal coatings. Carbon is used for X-ray analysis. A heavy coating (> 20 nm) is best for porous specimens, while 20 nm is good for X-ray analysis. 20 nm is required when using physical standards. Carbon coating thickness is measured by color changes on polished brass (Kerrick, et al, The Role of Carbon Film Thickness in Electron Microprobe Analysis, Amer. Min., 58, pp 920-925, 1973). A metal coating (Au, Pt/Pd, etc.) is used for imaging. Metal thickness is measured with a thin-film monitor. See the how-to sheets in the Specimen Prep lab for further information.

Standards for Microanalysis

Energy Calibration

X-ray peaks must occur at the "theoretical" energy position. It is especially important that the peak positions agree between the specimen and the standard. An energy calibration relocates peaks to their proper energy positions. The calibration is carried out on a copper specimen. See lab personnel for EDS calibration.

Operating conditions between Std and Spec (ED/WD same)

Beam Current

This is chosen to optimize the number of X-rays reaching the detector. For EDS the optimum beam current is 0.2 nA, or 25 - 30% dead time. For WDS an optimum beam current is 20 nA. Beam current is measured with the picoammeter and displayed in the dSspec window.

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