Don Grooms Course Evaluation Course evaluation question Is

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-tooxygen 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 Nano. SEM) • 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 m. A ion current – 30 seconds deposition time – 50 m. Torr 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 Nano. SEM 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

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

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

Stolen from Nicholas Richie Increases dead time

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

Preset options What kind of time? Live? Clock? Ro. I? Determines “Live Time” during which data are collected “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 20 - 40% 1. 6 μsec – 102. 4 μsec

Microscope control panel and return! Return to normal operating screen

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

Lower tray information Red while taking data Black when finished

Image Tab Your image here! Image Tab

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

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

• Si(Li) Detectors – Very common – Less expensive – Require LN 2 • SDD – – – The next big thing Handle higher count rates for mapping Do not require LN 2 Currently more expensive Slightly poorer resolution (operate at room temperature! • Microcalorimeter – Not a tool; a career!

Si(Li) Detector

Silicon Drift Detector

Microcalorimeter