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From: przemek@liszt.helios.nd.edu (Przemek Klosowski)
Newsgroups: comp.arch
Subject: Re: chip cost
Summary: Right? wrong? it all depends.
Keywords: nanoscale, chip, miniaturisation
Message-ID: <671@news.nd.edu>
Date: 9 Nov 90 22:43:37 GMT
References: <27547@mimsy.umd.edu> <780020@otter.hpl.hp.com>
Sender: news@news.nd.edu
Organization: University of Notre Dame,  Notre Dame
Lines: 32

In article <780020@otter.hpl.hp.com> tgg@otter.hpl.hp.com (Tom Gardner) writes:
>Chris Torek:
>   |want.  The problem is that yeild goes to zero.
>
>Not quite. Two interesting effects become apparent:
>  - as the conductors become smaller and closer together the electrons
>  tunnel from one conductor to a neighbouring one
>  - as the transistors and conductors become smaller then, for a given
>  current density (which is often a limiting factor), the current must
>  reduce. Eventually you reach the point where, due to the quantised nature
>  of current, there is a non-zero probability that there is no electron in
>  the conductor/transistor, even though there is, on average, a current 
>  flowing. 
Well, you are right, but also you are wrong. These effects indeed exist
but at much smaller scale than discussed. The tunnelling effect range
depends on the wavelength of electron and on the depth of the
potential well in which it is trapped (i.e. work function---energy needed
to take the free electron out of the conductor). In practical cases it will
be on the order of an 10-100 angstrom (10-100 * 1e-10m, or .001 to .01 micron.
Again, the electron charge is 1.6e-19 coulomb, so you need approx 1e13 of
the little critters for each microampere of current each second, or 1e4
per each nanosecond. It is still plenty. There is a whole 'semi'science
called nanotechnology, that deals with devices on the nanometer scale, where
these things matter. Nothing demonstrated yet, although I would say that 
MBE deposited superlattices look very promising (my thesis is on physics
of magnetism in such systems)

	przemek
--
			przemek klosowski (przemek@ndcva.cc.nd.edu)
			Physics Dept
			University of Notre Dame IN 46556