Whenever I read a super-enthusiastic news story about how devices based on new material XYZ are the greatest thing ever and are going to be an eventual replacement for silicon-based electronics, I immediately think that the latter clause is likely not true. People have gotten very spoiled by silicon (and to a lesser degree, III-V compound semiconductors like GaAs), and no wonder: it's at the heart of modern technology, and it seems like we are always coaxing new tricks out of it. Of course, that's because there have been millions of person-years worth of research on Si. Any new material system (be it graphene, metal oxide heterostructures, or whatever) starts out behind the eight ball by comparison. This paper on the arxiv this evening is an example of why this business is hard. It's about Bi2Se3, one of the materials classified as "topological insulators". These materials are meant to be bulk insulators (well, at low enough temperature; this one is actually a fairly small band gap semiconductor), with special "topologically protected" surface states. One problem is, very often the material ends up doped via defects, making the bulk relatively conductive. Another problem, as studied in this paper, is that exposure to air, even for a very brief time, dopes the material further, and creates a surface oxide layer that seems to hurt the surface states. This sort of problem crops up with many materials. It's truly impressive that we've learned how to deal with these issues in Si (where oxygen is not a dopant, but does lead to a surface oxide layer very quickly). This kind of work is very important and absolutely needs to be done well....
7 comments:
Even GaAs is a distant second to Si. Eletrically, chemically, mechanically, economically (raw material... sand), Si is a wonder.
As they say "GaAs is the material of the future, and always will be."
I get the feeling I heard this from somewhere else in the 60s....
"Nuclear fusion will be 10 years away"
So, what is your prediction for graphene? So much research is being done- everyone swears by it. Will it go the same way?
This sort of problem crops up with many materials. It's truly impressive that we've learned how to deal with these issues in Si .
This sort of problem crops up with many materials. It's truly impressive that we've learned how to deal with these issues in Si .
I get the feeling I heard this from somewhere else in the 60s....
One problem is, very often the material ends up doped via defects, making the bulk relatively conductive.
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