Breakerspace SEMPrep Ion Mill Tutorial

Overview:

Our ion mill enables damage free sample prep for SEM imaging. It is equipped with two ion guns: a high-energy gun with a 2-16 keV range, and a low-energy gun with a 0.1-2 keV range. We have sample holders for polishing, and for 30° and 90° slope cutting, with a handy microscope to help with sample alignment. Our LN2 cooling option allows milling of heat-sensitive samples with good temperature control.

Index:

Standard operating protocol - (startup, operation, shutdown)
Materials and sample prep
Detailed operating instructions
Data processing and analysis
Common failure modes
Manufacturer manuals
Links
Exercises

Standard operating protocol:

Instrument startup:

Turn the display on
Turn the TMP’s standby OFF
In case the TMP’s current consumption at 1500 Hz is higher than the usual, or >1 A, open the forevacuum pump’s bypass valve for approximately 10 minutes
Open the argon cylinder (in closet to left of instrument)
Press Purge (5s) four times, waiting five seconds between each click
Needle valve Semi-automatic control should be selected
Open the needle valve for the ion gun you will use to allow it to reach the preset pressure, then let it close automatically
Open the other ion source’s needle valve if it will be used during today’s operation

Operation:

Operation in semi-automatic operation mode:

Prepare sample for polishing or slope cutting
Load sample
Sample motion to be set
Milling angle to be set
Accelerating voltage to be set
Milling time to be set
Pressure must be <5x10^-6 mbar before turning on the ion source
Turn the ion source on and the sample will be prepared
Upon completion, unload sample. Note that cooled samples should be allowed to return to ambient temperature before unloading

Operation in automatic operation mode:

Prepare sample for polishing or slope cutting
Load sample
Switch to the automated thinning mode in Settings\Thinning
Open a recipe from the library, or create one
Pressure must be <5x10^-6 mbar before a recipe is run
Click “Run all steps” and the sample will be prepared according to the set steps
Upon completion, unload sample. Note that cooled samples should be allowed to return to ambient temperature before unloading

Instrument shut down:

Ensure that all high-voltages are turned off
Turn the sample movement off
Tilt the sample back to 0° milling angle
Open the shutter plate
Turn the camera and illumination(s) off
Ensure that the needle valve is closed
Turn the TMP’s standby ON
Close the argon cylinder
Turn off the monitor

Compatible materials and sample prep:

Samples should be non-hazardous and safe to handle in the Breakerspace
Samples should be free of volatiles (dry)
Samples must be free of loose particles (“flush” with compressed air)
Samples that are carefully polished or prepared before being ion milled will need less time to polish and yield better results

If you have any questions about whether a material is appropriate to characterize in the Breakerspace, please ask before bringing it to the lab.

Types of milling:

Polishing: Polishing is primarily done on metallographic samples that have been sectioned, mounted in a resin puck, ground, and mechanically polished to a reflective finish. Polishing can also be performed on other flat samples, though degree of success will depend on the initial preparation of the sample surface. During a polishing operation the sample is continuously rotated and the ion beam contacts the surface at a low angle (3° to 10°), for gentle sputtering of material from a larger spot, approximately the size of a pencil eraser. Starting at 10 kV and 4°, results can be obtained on a well-prepared sample in as little as 10-30 minutes.

Slope cutting: Slope cutting is done at a higher angle, using a slope cutting holder. We have 30° and 90° slope cutting holders. In slope cutting, the sample is mounted to a carrier plate, and partially shielded by a titanium mask.

30° slope cutting: Samples may be up to 5mm thick, 16mm wide, and 13mm long. In this operation a notch will be cut into the face of the sample, at the position of the mask. Longer processing times will result in larger/deeper notches. The back of the sample needs to be a flat surface that can be adhered to the carrier plate. Best results are achieved when the distance from the mask edge to the sample surface is uniform, which can be accomplished if the surface to be notched is parallel to the mounting surface. The notch will be centered on the sample, and will not cover the full width of larger samples.

90° slope cuttting: Samples may be up to 6mm thick, 16mm wide, and 20mm long. In this operation, a surface will be cut that is perpendicular to the surface adhered to the carrier plate. During 90° slope cutting, redeposition of material sputtered off the leading edge of the sample can be an issue. This can best be avoided by preparing samples with a clean, well-mechanically polished surface to be slope cut that is perpendicular to the mounting face, and will protrude a minimal and uniform amount above the mask.

Detailed operating instructions:

Data processing and analysis:

We recommend imaging your sample(s) in the SEM before ion milling. Before and after comparisons are interesting to have, and can also help troubleshoot the process in case the results are not as expected (surface not polished, surface damaged, etc.).