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hzbEMIL • Watching the Secret Lives of Atoms

Egg, spoon, vacuum

authored 4 years ago:

Chalcopyrites across town

Just in time for easter, Wolfram Calvet and Karsten Prietzel of the wider EMIL-team are embarking on their own version of an egg and spoon race. Early next week, they will be running the first in-situ transfer of a chalcopyrite thin film sample from the processing machine in Wannsee to the the CISSY diagnostic facility in Adlershof, on the other side of town.

This may not sound like too big a deal, and – actually – if it all works well, it won’t have been. But don’t (ever!) underestimate the amount of detail and planning that has to go into even a seemingly simple procedure like this. And there is still a lot that can go wrong.

First, the two machines, one in Wannsee, the other in Adlershof, were never made to work together. So they are not exactly compatible and there are quite a few of „non-standard“ pieces involved. And then, in order to be truly „in-situ“, the sample has to be kept in vacuum throughout the entire procedure. All contact with oxygen (or pretty much anything else) will make the sample useless. And then, minimised, but still real, there is always the risk of dropping the sample...

Once the big in-situ lab EMIL will be up and running, all this will happen on site, automatically and right in front of one of BESSY’s beamlines. But until then, this is the only way to test and prepare the analytical setup and to collect valuable experience.

It's more than just testing, though. With this transfer, it will - for the very first time - be possible to use photoelectron spectroscopy (PES) on the still quite mysterious surfaces of chalcopyrites without any oxygen or other contamination. Chalcopyrites are one of the big hopefuls among the new solar cell materials, so what happens at their surfaces is crucial information. With a little luck, the first such measurements will be made next week.

comments
  • authored 4 years ago:

    Thanks, Iver Lauermann, for putting things into perspective. I am still new to all this and I greatly appreciate background information from people who have known the field for years. Please keep it coming!

  • authored 4 years ago:

    Well, I think it would not be fair to some colleagues to leave this post uncommented because this one sentence is not quite right: "With this transfer, it will - for the very first time - be possible to use photoelectron spectroscopy (PES) on the still quite mysterious surfaces of chalcopyrites without any oxygen or other contamination." In fact, back in the nineties there was a system at the IPE (Institut für Physikalische Elektronik, http://www.ipe.uni-stuttgart.de) in Stuttgart that did exactly that. There, chalcopyrites could be deposited and analysed in the same machine without even the need for UHV transfer. Much of what we know today about this material and its surface was published then, e.g. by such well known researchers like Hans-Werner Schock, who was later director of HZB institute E-IT. So why then do we set up another system to repeat these measurements? The answer is that the chalcopyrite material that is made today can lead to solar cells with an efficiency of more than 20% and that this material is different from that back in the nineties with much lower device efficiency. So we need to understand the new material also. And if, one day, we understand why the new material is better, we might be able to turn just the right knob on our deposition machine to increase the efficiency even further….