You have a molecule. Something that will "stay put" probably written on a "2d" surface like Graphene.
Graphene is composed of lots of little hexagons. Each side of the hexagon can be broken and have an atom attached to it in "3d".
You have 6 sides and the angle break can go "up" or "down".
You can only use 3 sides however so that each hexagon has data and you can tell unique data.
This gives you 3 positions in 3 states, Up, down, or Flat.
0.142 nanometers per bond...
That's 27 states per hex, and 190 hexes per nanometer... 36,100 hexes per square nanometer...
I'm sure I screwed up a calculation in there somewhere. But Based on current tech this is my answer to what is possible to write. Now Reading might be a bit harder at any speed... but hey this is all theory right?
One cool idea (I saw it on Charles Stross' blog) is "diamond memory": use a diamond crystal, with two different isotopes of carbon for 1 and 0 bits. This also doesn't feel too unimaginable, in theory. According to Wolfram Alpha[1] this gives 1.75*10^23 bits (20 zettabytes) per CC.
Graphene is composed of lots of little hexagons. Each side of the hexagon can be broken and have an atom attached to it in "3d".
You have 6 sides and the angle break can go "up" or "down".
You can only use 3 sides however so that each hexagon has data and you can tell unique data.
This gives you 3 positions in 3 states, Up, down, or Flat. 0.142 nanometers per bond...
That's 27 states per hex, and 190 hexes per nanometer... 36,100 hexes per square nanometer...
I'm sure I screwed up a calculation in there somewhere. But Based on current tech this is my answer to what is possible to write. Now Reading might be a bit harder at any speed... but hey this is all theory right?