CREATING A SAMPLE FOR THE TEM

Focused Ion Beam (FIB)

How it works?

Reasons for one electron beam and one ion beam Viewing three dimensions

SEM provides view of x- and y-directions

FIB provides view of y- and z-directions

Monitoring sample fabrication with non-destructive SEM

Determining if the final sample is of uniform thickness Brightness of sample should be

consistent

How it works?

Eucentric height adjustments Sample holder is tilted back and forth Height (z-direction) is adjusted until the area of

interest remains centered at all tilts Both FIB and SEM can view the same area

Eucentric height is typically around 5mm in most FIBs

How it works?

Sample protection (Pt deposition) Wetting of tungsten tip to make

Ga+ ions Injection of Pt-based metallorganic

gas Pt is deposited and organics leave

Pt coating protects the area of interest from further ion damage

How it works?

Ion milling Trenches are created around the area of interest Milling is monitored by the SEM beam

Sample cutting Rectangular sample is cut so that it is barely attached

Pt

How it works?

View of milled sample

How it works?

Sample Plucking Pt gas probe reinserted Sample plucker is inserted Plucker is microwelded to the

sample TEM sample is lifted from the

bulk material

How it works?

Welding to the TEM grid Eucentric height of grid is found Sample is moved against the grid Sample is microwelded to the grid Plucker is ion milled off

How it works?

View of mounted sample

How it works?

Sample polishing Needed for atomic resolution in TEM Eliminates ion impurities from milling (surface

damage) Low current is used to prevent impurities and surface

damage Final sample is ~100nm thick Final sample must have parallel surfaces and

consistent thickness Final sample will be bright due to electron

transparency

What we are looking for

Grain boundary complexions

What we are looking for

A good high resolution TEM image of complexions