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Individual Atom Memory Created
azav writes "University of Wisconsin-Madison Scientists have created "atomic scale" memory using individual atoms of Silicon." A cool photo can be found on the site as well.
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If those are silicon atoms in the photo then what are the grooves in between the rows of atoms?
I know the secrets of the video game champs
In addition to requireing extra circuitry for decoding, this would require extra time. If you're wondering why CPUs don't just use various (16/32/64/whatever) voltage levels internally, then you really need a refresher course.
Transistor -> voltage controlled current source. i.e. a transister (in most cpus, these are nmos/pmos pairs) will either be "conducting" or "not conducting" a current depending on voltage level at the gate. Although technically these conducting/non-conducting will have slightly different currents flowing though them, we cannot use these as various voltage levels for the next transister because we get into all sorts of matching problems, fan-in/out problems, and basically (for example) the number "26" would be represented by one voltage level here, a different one there, and another one based on what transisters or conducting, and how much. If you're wondering why we don't use resisters to solve some of these problems, you REALLY need to review - power dicipated = current * current * resistance = heat. 20B currents squared * 20B resistances = instant chip incineration.
As a side note (actually two side notes) I beleive in the 40s they were experimenting with computers which used 10 voltage levels because that was the natuaral thing to do, until someone suggested using binary/boolean value which until that time were just a mathmatical curiosity than a dicipline taken seriously. I don't have references on hand ot back this up, but I think i remember reading something to that effect. The other side note is that many modems (even today) use variable-level voltages ot communicate. This is because the speed limiting factor effecting modems is line quality and length. It takes a relativly long time to force the line to any particular voltage, and so the modem makes these voltages count by encoding multiple levels. Ex. 9600bps modem uses 12 phase angles, four of which have two voltage levels, alowing to transmit 16 bits in one cycle (Stallings, Data & Computer Communications, 6th, p145). This is also why some modems (ex 56k) will only connect at (ex) 24k if excessive line noise prevents reliable encoding on many voltage levels.
The second reason we don't use variable levels in memory storage is error control. 1/0 values are screwed up enough by line noise, magnetic fields, and what have you. Imageine how difficult a time a machine would have dtermining "is that atom 23456 picometers about the base or 23457?"
As photonics emerges as a network technology though, I'm wondering if there is something like a "photo-transister" that will block or allow passthrough of light if light is present at a gate of a certain wavelegth. I know extreamly little about photonics, but if this possible then maybe multiple bits can be transmitted via multiple wavelengths inside a light-based (as opposed to electricity based) processor. Anyonw working on something like this?
Anyway, I hope this helps!
KeggInKenny
"A dictatorship would be a heck of a lot easier, there's no question about it." -George W. Bush
Actually, they are all rougly the same size, regardless of atomic weight. This is one of the interesting things about quantum mechanics and atomic physics. *All* atoms are between 0.5 and 2.5 Angstroms (1e-10 m)with Cesium being the largest (bigger than Uranium) and Nitrogen? being the smallest. Silicon isn't very large, however.
Hydrogen's the smallest, according to my books, with a radius of something like 0.53 angstroms (been a while since I looked it up).
What confuses me is why the atomic radii don't go up as the square of the number of shells. The alkali metals will have a single electron in the outermost shell, with the nucleus shielded by the inner shells, and so having an apparent charge of one. This seems to give a system with size equivalent to the nth energy level of an electron in hydrogen, which goes up as the square of the shell number.
I and the friends I asked about this speculate that because the electrons in the sheilding shells are smeared out radially, the outermost shielding shell extends past the valence shell's nominal radius, and so the core is only partly shielded, but I haven't seen any description to date of how you work out what the radii actually end up being.
Any pointers/quick explanations?