www.cs.wisc.edu/~kovar/hall.html -> www.cs.wisc.edu/%7Ekovar/hall.html
Kovar/Hall Electron Band Structure In Germanium, My Ass Abstract: The exponential dependence of resistivity on temperature in germanium is found to be a great big lie. My careful theoretical modeling and painstaking experimentation reveal 1 that my equipment is crap, as are all the available texts on the subject and 2 that this whole exercise was a complete waste of my time. Introduction Electrons in germanium are confined to well-defined energy bands that are separated by forbidden regions of zero charge-carrier density. You can read about it yourself if you want to, although I dont recommend it. Youll have to wade through an obtuse, convoluted discussion about considering an arbitrary number of non-coupled harmonic-oscillator potentials and taking limits and so on. The upshot is that if you heat up a sample of germanium, electrons will jump from a non-conductive energy band to a conductive one, thereby creating a measurable change in resistivity. This relation between temperature and resistivity can be shown to be exponential in certain temperature regimes by waving your hands and chanting to first order. Experiment procedure I sifted through the box of germanium crystals and chose the one that appeared to be the least cracked. Then I soldered wires onto the crystal in the spots shown in figure 2b of Lab Handout 32. The solder simply wont stick, and you can forget about getting any of the grad students in the solid state labs to help you out. Once the wires were in place, I attached them as appropriate to the second-rate equipment I scavenged from the back of the lab, none of which worked properly. I soon wised up and swiped replacements from the well-stocked research labs. This is how they treat undergrads around here: they give you broken tools and then dont understand why you dont get any results.
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