Low Temperature Resistivity

The temperature dependence of electrical resistivity was measured for three materials: a conductor (copper), a semiconductor (a carbon resistor), and a doped semiconductor (a pn junction). As expected, the resistance of the copper sample decreased with temperature and the resistance of the carbon resistor increased with temperature. The temperature coefficient of resistance of Cu was calculated to be α = 0.0040± 0.0002 1/C; the accepted value of 0.0039 is within this uncertainty. From the nonlinear behavior of the pn junction, the the band gap energy of pure Si was calculated to be EG = 1.2± 0.1 eV; the accepted value of 1.12 eV is within this uncertainty. No quantitative measurements could be made from the carbon data, due to limitations in the theory and to the fact that a carbon resistor is not a pure semiconductor.