- #1
andrewr
- 263
- 0
Hi,
I had a question that maybe someone might know, and that although I have been researching it I am not finding enough information on the web that would solve the issue. (it's the end of the month, too... and being broke and in a hurry is a problem too...)
The project is aimed at saving lives of our USA military (not killing anyone) -- and is guaranteed to do that -- but it's overall usefulness and deploy/logistics issues need to be improved or it might not get used effectively -- and, as I am not in this for the money or with money -- I have some final hurdles to cross before I can improve the item to a level I am *confident* in..
Size and heat are two issues that can be improved, but I lack some specific information to design a robust compensation circuit for unusually hot and cold temperatures (antartica anyone?)
It all boils down to accurate thermodynamics of Silicon... (not exotic new semiconductors...hybrids)
The effective mass of electrons in semiconductor material show a directional dependency; in most texts there are two orientations listed out for for E(k) diagrams. The directions are <111> and <100>
From common knowledge, it's evident that the lattice (atomic) spacing is different depending on which way one observes the crystal. The lattice spacing produces the band changes and affects the energy gap (Bloch theorem too); so it is ideal for use in a simplistic model to attempt to design a better version and look for flaws in the models I have.
I found the "lattice spacing" for silicon (nearly pure) from 0K to melting online in a table -- but it is only for one direction in the crystal and I don't know if it is in vacuum or not. (I'm still happy with it...!) At 300K the chart reads 0.5431092 angstrom... Looking at the chart, I noticed that near 2K, there is a reversal in the contraction rate much like water at 4C begins to expand again before forming ice. This suggests to me that there is a dynamic motion of of the molecular bonds which packs silicon more tightly depending on relative angle (not just vibration length) of the bonds at different temperatures. That makes me uncomfortable with just assuming that the lattice size changes uniformly (scalar) in both directions -- I can (and will) model with that assumption; but I would prefer to KNOW that is a safe assumption by reviewing some studies...
So, I am wondering if anyone has come across the same kind of thermodynamic data (preferably as spacing and not as temperature coefficient) for a different direction and knows where it might be buried on the web. I am interested in graphs (as long as they are big enough to make reasonable estimates from), tables (I love those!), curve fits -- (less trustworthy) -- for silicon that show the nonlinear expansion effects in other crystal directions OR Information for doped silicon in the same or other direction when the doping concentration is given. I can sort out the dopant later...but knowing the approximate dopant level (1 order of magnitude is OK) is important...
Most industry doping is off +-100% from manufacturer to manufacturer anyway. And multiple manufacturers of parts is a good thing for sustainability... (I'm not going to be making the parts...)
Thanks in advance.
I had a question that maybe someone might know, and that although I have been researching it I am not finding enough information on the web that would solve the issue. (it's the end of the month, too... and being broke and in a hurry is a problem too...)
The project is aimed at saving lives of our USA military (not killing anyone) -- and is guaranteed to do that -- but it's overall usefulness and deploy/logistics issues need to be improved or it might not get used effectively -- and, as I am not in this for the money or with money -- I have some final hurdles to cross before I can improve the item to a level I am *confident* in..
Size and heat are two issues that can be improved, but I lack some specific information to design a robust compensation circuit for unusually hot and cold temperatures (antartica anyone?)
It all boils down to accurate thermodynamics of Silicon... (not exotic new semiconductors...hybrids)
The effective mass of electrons in semiconductor material show a directional dependency; in most texts there are two orientations listed out for for E(k) diagrams. The directions are <111> and <100>
From common knowledge, it's evident that the lattice (atomic) spacing is different depending on which way one observes the crystal. The lattice spacing produces the band changes and affects the energy gap (Bloch theorem too); so it is ideal for use in a simplistic model to attempt to design a better version and look for flaws in the models I have.
I found the "lattice spacing" for silicon (nearly pure) from 0K to melting online in a table -- but it is only for one direction in the crystal and I don't know if it is in vacuum or not. (I'm still happy with it...!) At 300K the chart reads 0.5431092 angstrom... Looking at the chart, I noticed that near 2K, there is a reversal in the contraction rate much like water at 4C begins to expand again before forming ice. This suggests to me that there is a dynamic motion of of the molecular bonds which packs silicon more tightly depending on relative angle (not just vibration length) of the bonds at different temperatures. That makes me uncomfortable with just assuming that the lattice size changes uniformly (scalar) in both directions -- I can (and will) model with that assumption; but I would prefer to KNOW that is a safe assumption by reviewing some studies...
So, I am wondering if anyone has come across the same kind of thermodynamic data (preferably as spacing and not as temperature coefficient) for a different direction and knows where it might be buried on the web. I am interested in graphs (as long as they are big enough to make reasonable estimates from), tables (I love those!), curve fits -- (less trustworthy) -- for silicon that show the nonlinear expansion effects in other crystal directions OR Information for doped silicon in the same or other direction when the doping concentration is given. I can sort out the dopant later...but knowing the approximate dopant level (1 order of magnitude is OK) is important...
Most industry doping is off +-100% from manufacturer to manufacturer anyway. And multiple manufacturers of parts is a good thing for sustainability... (I'm not going to be making the parts...)
Thanks in advance.