For years graphene has proved a cruel temptress for the semiconductor avant garde. The material - a layer of carbon atoms grouped in the ever popular honeycomb lattice - promised major performance gains over silicon. The problem with the stuff, however, has been arranging it in a large enough layer to replicate the 8- to 12-inch …
...is the opposite direction to electron flow, if I remember correctly.
"For years graphene has proved a cruel temptress for the semiconductor avant garde."
I vote this to be 2007's most pretentious opening gambit for an article. Well done!
At this rate Ashlee, you'll end up being quoted in Private Eye... (good/bad in equal measure)
Hole flow is simple enough to visualize. Take a row of seats filled with bums except for one seat. Person next to the empty seat moves into it, leaving their own seat empty. Next person does the same, etc. The "empty seat" flows in the opposite direction to the bums.
Semiconductors come in N-type where some atoms have a spare electron and P-type where some atoms are short one electron. In P-type semiconductors the atoms with the deficiency are called "hole sites". Apply a voltage to a P-type and electrons flow by jumping into holes, leaving holes behind them, etc. The holes "flow" in the opposite direction.
Yup, the holes are the conceptual spaces left behind as each electron jumps to the next space that its neighbour has just vacated in a weird kind of marble-solitaire way. Early discoverers of electricity had to guess which way the current flowed and they guessed wrong, so that conventional current is always described in diagrams as flowing from positive to negative in the same direction that the holes appear to move. Electrons actually flow from negative ( cathode ) to positive ( anode ) in the opposite direction.
Cell phones and high power output ?
Somebody call Mothers Against Cell Phone Cancer ! They're gonna make our brains melt if we don't pay attention !
Last time I heard "Hole Flow"...
...had to be around '74, when the USAF was teaching me everything I didn't yet know about electronics.
Darned Heathkit never mentioned holes, but they clearly indicated current flow was opposite to electron flow; my, how much I learned back then :D and had forgotten since!
Im still a bit put off by a void (hole) being the carrier of current...my brain has successfully wrapped itself around the concept, but it still reeks of error!
I always wondered when Carbon would be used for semi-conductors, as it is next in line in the periodic table after germanium and silicon, but I always assumed it would be the crystaline form, (as are semi-conductor germanium and silicon) i.e. diamond.
I guess graphite is a crystal, but only in two dimensions.
Substances that conduct heat and insulate electricity well are rare. Beryllium Oxide is one, (and dangerous, used to insulate RF transistor collector/Substrate from heatsink to allow emitter to be earthed).
Diamond is also unusual in that it is an excellent heat conductor but also a good insulator. Hence the diamond allotrope of carbon is no use as a semiconductor. It's also difficult to grow diamond crystals the size fab labs are used to with silicon :-)
Graphene and nano-tube carbon structures can though make devices.
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