Technical Articles by Bell System Authors Not Appearing in the BellSystem Technical Journal

and that which can be boiled. Some of the melted metal lands on the negative electrode and, with repetition of the phenomenon, results in a mound of metal transferred from the anode to the cathode. This transfer, which is about 4 X 10-" cc of metal per erg, is the erosion which occurs on the make of electrical contacts. The arc voltage is of the order of 15. If the initial circuit potential is more than about 50 volts, there m a y be more than one arc discharge, successive discharges being in opposite directions and resulting in the transfer of metal in opposite directions--always to the electrode which is negative. The occurrence of an arc is dependent upon the condition of the electrode surfaces and upon the circuit inductance. For "inactive" surfaces an arc does not occur for inductances greater than about 3 microhenries. Platinum surfaces can be "activated" by various organic vapors, and in the active condition they give arcs even when the circuit inductance is greater than this limiting value by a factor of 103. The Conductivity of Silicon and Germanium as A ffecled by Chemically Introduced Impurities. G. L. PEARSON.1 Paper presented at A. I. E. E., Swampscott, Mass., June 20-24, 1949. Included in compilation on semiconductors. Elec. EnggV. 68, pp. 1047-1056, Dec. 1949. ABSTRACT--Silicon and germanium are semiconductors whose electrical properties are highly dependent upon the amount of impurities present. For example, the intrinsic conductivity of pure silicon at room temperature is 4 X 10~6 (ohm c m ) - 1 and the addition of one boron atom for each million silicon atoms increases this to 0.8 (ohm cm) - 1 , a factor of 2 X 105.