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Science Forum Index » Nanotechnology Forum » can a treatment of surface modify pressure?
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| dau.mic |
 Posted: Sun Jul 16, 2006 10:42 pm |
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Guest
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Sorry, I repeat my message with the correct location
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I propose you the following conjecture: can a treatment of surface modify
pressure?
The electronic industry uses a great amount of single-crystal silicon. This
matter is also employed for the creation of miniaturized mechanical devices.
The tools of this new industry are the same used in electronic industry:
etching, doping, epitaxial deposition, thermomigration and more. For making
micro-mechanical structures, etching is the most versatile tool. Chemical
etchants for single-crystal silicon are numerous. Some of these etchants are
anisotropic: the speed of etching is dependent of crystallographic
orientation of exposed silicon. For example, KOH in water generates on a
silicon area with a crystallographic orientation named <100> a pyramidal
pit. The crystallographic orientation of the planes of the pit is in this
case <111>. If E is the side of square entry of the pit, its depth P is
calculated by the formula: P = E / 1.414. With the other tools of electronic
industry, photolithography and masking, this sort of pyramidal pit could be
generated in great number and in small dimensions on single-crystal silicon.
The possibility to make these pits in great number and in very small
dimensions incited me to test the hypothesis: what could be the comportment
of a gas in a pit when its dimensions are smaller than the mean free path of
gas molecules?
For this purpose, I have made a software with Visual Basic (Windows
version). This software named Pyramid simulates the comportment of gas
molecules in a pyramidal pit. This simulation is very simple: the trajectory
of each gas molecule is determined one after one. The simulation is
realistic only in the case when the dimensions of the pit are smaller than
the mean free path of gas molecules (for example, the mean free path of
atmosphere at sea level is in order of 70 nanometres). With this condition,
a gas molecule that enters in the cavity could have a shock or more on the
planes without contact another gas molecule. The shock of gas molecules on
solid planes are supposed elastic. After each contact of molecule on solid,
the software calculates the new trajectory of molecule and the exchanged
impulses until the gas molecule leave the pit.
The errors of the software are avoided by two processes. The geometrical
process verifies the absence of abnormal trajectories. The physical process
survey the stability of the speed modulus of gas molecule between entry and
exit of the pit (the shocks are elastic so the speed modulus of molecules
must be constant).
The result of the simulation is surprising: the shocks of gas molecules in
the pit generate an overpressure. This overpressure represents 10% of the
normal pressure when the pit is absent. Simultaneously, the flight movement
of gas molecules when they leave the pit is enhanced.
Has this phenomenon any chance to be real?
For your judgement, the software Pyramid can be found here:
http://simulation.servehttp.com
It contains a detailed presentation of simulation (in French). |
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