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So let's say you were going to send some electronics to the bottom of the ocean, 3-5km down. This would be about $5km*1000kg=5Mkgf/m^{2}$. So at what pressure do circuit boards, transistors, etc stop working? Apparently there's a thing called the quantum critical point which some semiconductors break down. Although in this example the semiconductor broke down at about 10x the pressure that I'd be dealing with, I'm wondering if there are other known issues at these pressures with electronics?

My hypothetical specifically would exist as some circuits/computer hardware in caster oil (so salt water can't short it and the oil remains relatively incompressible), where instead of making the container withstand the pressure difference and keep the internals at 1atm, the contain might flex just enough so that the pressure inside is the same as the outside. So I'm wondering what kind of semiconductors/etc might break down under high pressures? Or if there's any other properties I might be missing?

Thanks for your time

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closed as off-topic by Emilio Pisanty, ZeroTheHero, Jon Custer, Buzz, Kyle Kanos Jan 1 at 15:27

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I'm not sure what kind of breakdown you have in mind, but most nonmetals are expected to become metallic (which would imply loss of all semiconductor properties) under sufficiently high pressure. This is called the Mott transition, and is behind a major effort to produce (and study) metallic hydrogen.

The mechanism is narrowing of the 'band gap' (about 1.1 eV in silicon) so that the conduction and valence bands overlap. If the narrowing were linear (it isn't), the -1.4 meV/kbar observed Si bandgap pressure coefficient would predict metallic behavior at 800 kbar or so, maybe ten million pounds per square inch. Oceans aren't deep enough for that, and water isn't liquid at that pressure anyhow.

This paper Theoretical Study of Energy Gap has more information.

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  • $\begingroup$ Thanks for the link, I read it and it was really interesting. So it looks to me like the takeaway is under higher pressures there's a larger (or smaller dep on the semiconductor) band gap energy but for pressures at the bottom of the ocean it'd be negligible (a fraction of an eV, which I assume is within the margin of error for transistors on chips &c). And I guess by breakdown I didn't mean in a technical sense, I just meant any condition where something like a raspberry pi would stop working because of surrounding pressure. $\endgroup$ – haxonek Jan 1 at 0:25
  • $\begingroup$ @haxonek - the prediction always broadens the energy bands, usually that means narrowing the gap under pressure (but there's other pressure effects that can happen simultaneously). A raspberry pi with a quartz crystal has a more immediate effect when that vibrating item gets its container crushed at depth... $\endgroup$ – Whit3rd Jan 1 at 1:41

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