Ultra thin Au layer is used for metal assisted chemical etching on various semiconductors. It works as a catalyst. Is it possible for Au to be diffused into Ge at room temperature if it is used for metal assisted chemical etching? If the diffusion indeed happens, how much it should be diffused to work as deep level defects?
We may be able to detect this using XPS. Can XPS determine whether enough Au is diffused so that it can make deep level defects?
Dear Munho KIm,
I feel that yes, Au can diffuse into Ge monocrystal at room temperature if suffcient time has elapsed. In Silicon, which I believe is harder to diffuse into, 5 years at room temperature has been sufficient for the Au to diffuse sufficiently deep to form Au deep levels (there are two Au energy levels in the Si band gap).
But be aware that the necessary depth is determined by the deep level energy position (the level has to cross the chemical/electrochemical potential of your Ge crystal) in order to be "seen" experimentally (DLTS or EIS-Electrical Impedance Spectroscopy).
Perhaps this will help
With best regards
Petr
If there is any diffusion ongoing you may have quite good chances to detect it down to ca. 0.1 at% level with XPS as the Au 4f cross section is relatively high
Dear all,
Thanks much for your comments.
I have a question for Dr. Greczynski. I have XPS plots on Au 4f measured from two single-crystalline Ge. Top one is the Ge with no Au and bottom one is from the Ge with possible Au diffusion. Based on this, can we conclude that Au was diffused which is enough for creating deep level defects? I couldn't see any Au (even particles) left from that sample in SEM. I used Au etchant to completely remove Au from the sample. Is there a chance that some invisible Au is left if we can't tell Au was diffused into the Ge from the XPS plot?
Regards,
Munho Kim
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