Flash memory and electron tunneling

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Brzohn
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Flash memory depends on tunneling in order to work—electrons have to tunnel through an oxide layer. Now, the wavelength of an electron is at most 24 pm. An atom is on the order of 100 nm wide, and the oxide layer must be at least several atoms thick. How can there be any significant tunneling?
 
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  • #2
Brzohn said:
Flash memory depends on tunneling in order to work—electrons have to tunnel through an oxide layer. Now, the wavelength of an electron is at most 24 pm. An atom is on the order of 100 nm wide, and the oxide layer must be at least several atoms thick. How can there be any significant tunneling?
The de Broglie wavelength ##\lambda_B## of an electron can be arbitrarily large for a slow-enough speed. According to this calculator, ##\lambda_B=24\text{ pm}## corresponds to a voltage difference of over ##2500\text{ V}##! For flash memory, a more realistic working potential is ##5\text{ V}##, which gives ##\lambda_B=550\text{ pm}##, i.e., big enough to tunnel through layers several atoms thick.
 
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  • #3
Brzohn said:
Flash memory depends on tunneling in order to work—electrons have to tunnel through an oxide layer. Now, the wavelength of an electron is at most 24 pm. An atom is on the order of 100 nm wide, and the oxide layer must be at least several atoms thick. How can there be any significant tunneling?
No, that is not correct. An atom is of the order of 0.1nm (=1 Angstrom) "wide".
The typical thickness for the oxide layers used in electronic devices is a few nm; but thinner (down to a 2-3 atomic layers) and thicker (sometimes much thicker) layers are also used.
 
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