[extropy-chat] diffraction limit

[Dan Clemmensen]

scerir wrote:

>>Also, there was a lot of talk 3-5 years ago about the efforts to produce
>>even shorter wavelength beams (effectively X-rays) and there were several
>>reports if I recall correctly of capabilities of producing feature sizes
>>as small as 10nm.  But I haven't heard anything about these recently.
>>Do you know if these methods are still being worked on? 
>>Thanks,
>>Robert
>>    
>>
>
>I remember I've seen papers showing that below 20nm 
>start "tunnelling effects". (?)
>
>  
>
This requires 4 answers. Basically, the question is whether or not the 
designer can use a classical analysis a quantum analysis, or both.

1) Theoretically, there is no upper limit of the length for quantum 
tunneling effects, but as a practical matter they are undetectable above 
some upper bound.

2) There is an upper bound on the length at which quantum tunneling 
becomes practically useful.

3) There is a lower bound on the length at which quantum effects can be 
practically ignored.

4) There is a lower bound on the length at which a classical model can 
be used at all.

(Can a real physicist please supply these dimensions?)

I really don't know where these bounds are. The existence of (4) makes 
me very skeptical of nano-electronics.  Therefore, I'm very happy that 
Drexler's "Nanosystems" analyzes nanomechanical systems instead of 
nano-electronic systems. Quantum uncertainty for a mechanical component 
is four orders of magnitude smaller than for an electron, and can 
therefore be ignored at the atomic scale. (Four orders of magnitude, 
because carbon atom weighs more than 10,000 times as much as an electron.)