How long does sample exchange require compared to the Phenom SEM?
Our SEM system’s have a medium size chamber that reaches its vacuum level in roughly 2.5 to 3 minutes. It can be opened in about 30 seconds from pressing “exchange” on the SEM’s front panel.
The Phenom SEM is able to exchange samples in around 30 seconds which on the surface, sounds attractive but this ability comes with a price. The Phenom SEM utilizes a unique design compared to standard SEM design by using both a column isolation valve to maintain column vacuum full-time, and a special sample holder design that is unlike any other SEM marketed.
As with many feature comparisons, there are caveats to consider. First, the SEC systems allow loading multiple samples at once while the Phenom Pro/ProX typically works with one sample at a time. So, while a single sample load time is faster with the Phenom, loading multiple samples would have the opposite result in total time required to images 4 or more samples for instance. Note that the Phenom Pro XL has ability to load multiple samples so this argument would not apply in that situation.
The Phenom Pro’s unique sample carriers are quite innovative but they also mean the maximum sample size is quite limited compared to other SEM’s with the exception of the Phenom XL which has a larger chamber. This smaller space for samples also means it is easier (faster) to evacuate that small chamber.
The CeB6 source of the Phenom requires a higher vacuum level and maintains the column at vacuum 24/7 which contributes to its ability of fast sample exchange times. See our other FAQ on Tungsten vs CeB6 sources for more info. Due to the high vacuum nature of the Phenom column, the column cannot be easily cleaned by the user. Particles from samples entering the column can be a concern for that reason and as such, Phenom suggests blowing and gentle tapping to remove loose particles on an SEM stub holding a powder or particle sample. Note though that this would then change the population statistics of a sample to be analyzed.
If your SEM workflow requires fast sample analysis, we encourage you to explain that process to your supplier. There are often alternatives and other factors to consider. If fast analysis is truly required, one possible solution is the use of a sample exchange device which can be even faster than Phenom’s exchange time. These are commonly used in large chamber SEMs. Once such device is offered by Quroum Technologies (LINK). This device allows keeping the SEM chamber at vacuum and utilizes and external sample exchange chamber. One advantage to this method is that the sample can be transported under an inert gas blanket at all times if necessary. This type of sample exchange system can be adapted to the SEC SEM systems.