Re: How many electrons per bit?
For 20nm planer flash the number of electrons per level dropped to under 10. 3D nand uses a larger geometry (40nm?) so there are more electrons per level. It looks like about 20 on the graph near then end of this. As far as I know the geometry is not shrinking any more and the extra capacity comes from more layers per die, more dies in a stack and putting the control circuits on a separate die instead of around the edge so the whole area of the die can contain layers of cells.