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ELECTRICAL AND OPTICAL PROPERTIES OF GRAY TIN.
NORTHWESTERN UNIV EVANSTON ILL
Extensive measurements of conductivity, magnetoresistance, Hall effect and thermoelectric power were made of polycrystalline filaments in the temperature range from 77 to 273K. The results, in general, tended to confirm the view that gray tin was a semiconductor of small, but finite, band gap. Discovery of a method of growing single crystals permitted useful measurements of the optical reflectivity. The single crystals made possible the investigation of the dependence of transport properties on crystal orientation. Magnetoresistance measurements as function of crystal orientation together with subsequent measurements of the oscillatory component of the low temperature magnetoresistance, provided experimental evidence basic to the currently accepted band structure model. The most remarkable feature of this model is the zero gap between the lowest conduction band edge and the uppermost valence band. The measured 0.08eV energy separation, originally believed to be the band gap, is, in fact, the separation between the lowest and secondary minima of the conduction band. According to the new model, gray tin occupies a unique position between the typical semiconductors finite band gaps and the semimetals in which the bands overlap.
Final rept. for Sep 54-Nov 64,
Research supported in part by the Advanced Research Projects Agency, Washington, D. C.
Contract Number 2: