Don Groom’s Course Evaluation Course evaluation question: “Is the instructor aware of the students’ limitations?” Student response: “Yes, and vice versa.”

Experiment You want to measure the aluminum-to- oxygen ratio in sapphire –Why? –“Flat, smooth and polished” Sapphire is known to be a poor conductor Options –Coat –Run in low vac (incompatible with current detectors on Nova NanoSEM) What is the effect of coating on the x-ray intensities?

Homework for Monday Absorption of X-rays is determined by the Mass Absorption Coefficient, μ/ρ. (Note that μ/ρ is a single entity; nobody ever lists μ alone.) This is a standard Beer’s Law absorption phenomenon: I(t) = I 0 *exp[-(μ/ρ)* ρ*t] where ρ is the mass density of the absorber and t is its thickness.

Mass absorption coefficient for carbon At what energies do we want to know the MAC?

How were samples coated? Recipe that came with the Denton Desk II sputter coater –45 mA ion current –30 seconds deposition time –50 mTorr Ar pressure –10 nm Gold coating For what purpose!!! What is the impact of this coating on Quantitative EDS Analysis???

Coatings used in your experiment Gold sputtered for 30 seconds Gold sputtered for 10 seconds Gold sputtered for 3 seconds (not used) Carbon evaporated thermally –Evaporated onto flat, smooth, polished sapphire –Evaporated onto rough alumina crucible

Lab reports Address the definition of “flat, smooth and polished” –Make a crude estimate of how rough the crucible bottom really is. Project what will happen to measured ratios of constituents whose Z varies by amounts much larger than aluminum and oxygen…like tungsten and oxygen. Tiwari is oxidizing niobium. –Can you help him determine the stoichiometry of his product?

Next Aphorism We never have time to do things right the first time. We always have time to do them again.

Labs: This Week and Next What is the working distance for which the EDAX system was designed? –Measure (and plot) count rate as a function of Z –Be sure to carefully link first. –Problems with moving to a taller sample when the working distance is 3.5 mm –Is it the same for Nova NanoSEM and Quanta and Leo? What is the probe insertion depth for which the EDAX system was designed? –Measure (and plot) count rate as a function of probe insertion depth

“Trust but verify.” Ronald Reagan

Count rates What is a reasonable range for count rates? –What is the cost if you use a count rate that is too high? –What is the cost if the count rate is too low? –How do you adjust the count rate?

Dead time What does “dead time” mean? How do you adjust dead time? What is an acceptable range of values for dead time?

Amp Time Integration time over which signal is averaged to establish a baseline from which the height of the “voltage step” is measured

Stolen from Nicholas Richie Poorer Quantitative results Shorter dead time (Amp time)

Plagiarism If you steal from one, it’s plagiarism If you steal from many, it’s research –R. Polson

Increases dead time Stolen from Nicholas Richie

Genesis icons continued EDS really has only three adjustable parameters: Collection time Amp time Count rate How do you adjust the count rate?

Preset options Determines “Live Time” during which data are collected What kind of time? Live? Clock? RoI? “None” is also an option What happens when you select it?

Dead time Kinds of time –Live time: time during which detector takes data –Dead time: time during which current accumulation window is closed –Clock time Sum of live and dead time Actual time we all know and love

Amp time: adjust for dead time of % 1.6 μsec – μsec

Microscope control panel and return! Return to normal operating screen

Peak ID Labels from spectrum Halographic Peak Determination: fits spectrum with theoretical sum Possible matches for energy where cursor is located Move to list of labeled peaks

Lower tray information Red while taking data Black when finished

Image Tab Your image here!

Top Center Icons Return control to microscope! Raster Full Reduced Spot User drawn

Collect Image

Brightness and contrast adjust in counterintuitive direction Use low resolution and few strips for faster feedback.

Random Notes Qualitative analysis –All peaks in the spectrum must be present –Will appear as colored lines when you click on an element in the list of options

Detectors Si(Li) –Very common –Less expensive –Require LN2 SDD –The next big thing –Handle higher count rates for mapping –Do not require LN2 –Currently more expensive –Slightly poorer resolution (operate at room temperature! Microcalorimeter –Not a tool; a career!

Si(Li) Detector

Silicon Drift Detector

Microcalorimeter