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Piezoresistive Coefficients
Posted 9 apr 2013, 13:45 GMT-4 MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.2, Version 4.2a, Version 4.3, Version 4.3b 3 Replies
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I want to find out the sensitivity of my piezoresitive cantilver beam. In order to do that, based on the equations, I should have the piezoresistive coefficient (Pi-1):
Delta-R/R=(PI-1)*maximum surface stress
In the materiel properties of polysilicon i have a matrix for piezoresitive coupling factor which I believe should give me the coefficient that I need to use in the equation. However, there is a "sigma" parameter in that I do not know what is its value, since i did not define that.
Can anyone help me with this?
here is the matrix that is defined by comsol :
{58.8e-11[1/Pa]/sigma0(nd[m^3])[S/m], -27.2e-11[1/Pa]/sigma0(nd[m^3])[S/m], 58.8e-11[1/Pa]/sigma0(nd[m^3])[S/m], -27.2e-11[1/Pa]/sigma0(nd[m^3])[S/m], -27.2e-11[1/Pa]/sigma0(nd[m^3])[S/m], 58.8e-11[1/Pa]/sigma0(nd[m^3])[S/m], 0, 0, 0, 85.9e-11[1/Pa]/sigma0(nd[m^3])[S/m], 0, 0, 0, 0, 85.9e-11[1/Pa]/sigma0(nd[m^3])[S/m], 0, 0, 0, 0, 0, 85.9e-11[1/Pa]/sigma0(nd[m^3])[S/m]}
Best Regards
Bahar
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if you open up all the material nodes and sub-nodes you will find the analytical definition of "sigma0" (you might need to turn on the options preferences show advanced or all (COMSOL hides some of it's complexity ba default, I finally run with all open, much more fun and interesting to learn about ;)
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Good luck
Ivar
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Do you know what this nd = (Number density) parameter represents.
the formula used for conductivity (Sigma0) looks like fitting function based on the electron charge (e_const).
Does (nd) refer to number of electrons (or free charges). Does it have any relation with the doping concentration defined in the piezoresistive or conductive parts?
Thanks
Mohamed
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Do you know what this nd = (Number density) parameter represents.
the formula used for conductivity (Sigma0) looks like fitting function based on the electron charge (e_const).
Does (nd) refer to number of electrons (or free charges). Does it have any relation with the doping concentration defined in the piezoresistive or conductive parts?
Thanks
Mohamed