What is the maximum coating area over which a uniformly thick coating of 10-25nm can be applied? (This is important, as we often get geological petrographic sections for EPMA that measure ~7cm diagonal.)
The Desk V HP has a 6” (~15cm) diameter chamber. Inside, the standard specimen table is 2” (5cm) diameter and can tilt and rotate (without the etch option). We can upgrade the sample stage to a flat 4” (10cm) diameter but the sample can only rotate, it will not tilt. If a larger sample size is required, it would fit better in the Bench Top Turbo.
For carbon evaporation, the coatings are quite uniform over the 4” (10cm) diameter size. Topography of the sample can cause shadowing. And carbon particulates can also be known to affect the coating thickness uniformity if they fall from the carbon source onto the specimen during coating. The Bench Top Turbo geometry allows coating the specimen while the carbon source is not directly above the sample. If any particles fall from the carbon, they do not land on your sample.
The monitor will last for many years and is covered under the Denton standard 12-month warranty. The gold coated quartz crystals themselves need to be changed periodically when there is a thick build-up of coating on them.
The process is fast. Total time to pump down and evaporate the carbon is in the minutes range, usually less than 10 minutes. A 0.125” reduced cross section of 0.040” diameter will deposit about 100 Å of carbon.
In the Desk V units, the sample must be relatively thin (on the order of 1” or less).
We do incorporate a safety interlock that will only power the carbon accessory when the vacuum interlock is satisfied. There are not built-in safeguards for eye protection; we recommend welding glasses or similar.
Compressed gas is not required. In the event that the unit is used for sputtering, argon is optional and room air can sometimes be used.
With an initial pressure of < 20 mTorr, a source-to-substrate distance of 2.375 inches (60 mm) using a timed sputter setting of 10 minutes (600 seconds), you can reasonably expect:
For gold, using air at 50 mTorr, a film thickness between 260 and 1750 angstroms and a deposition rate of between .43 and 2.92 angstroms, depending on power percentage and current applied (mAmps).
For gold/palladium using air at 50 mTorr, a film thickness between 405 and 2210 angstroms and a deposition rate of between .68 and 3.68 angstroms, depending on power percentage and current applied (mAmps).
For gold, using argon gas at 50 mTorr, a film thickness between 640 and 3360 angstroms and a deposition rate of between 1.07 and 5.60 angstroms, depending on power percentage and current applied (mAmps).
For gold/palladium, using argon gas at 50 mTorr, a film thickness between 560 and 2795 angstroms and a deposition rate of between .93 and 4.66 angstroms, depending on power percentage and current applied (mAmps).