Lanthanum was dissolved in CuO and the effects of La on the electrical cond
uctivity of CuO were investigated in order to control the hole concentratio
n and clarify the conduction mechanism of CuO that exhibits a p-type semico
nductivity. The maximum amount of La dissolved in CuO was evaluated to be 0
.5 mol% by powder X-ray diffraction. The conductivities for La-doped CuO we
re investigated by 4-probe and 3-probe methods. The temperature dependence
of conductivity showed that CuO has two conduction mechanisms in the temper
ature range of 50 degrees C to 900 degrees C; conductivity at more than 600
degrees C was independent of atmosphere and the amount of La, whereas cond
uctivity below 500 degrees C increased with an increase in partial oxygen p
ressure (P-O2) and amount of La. Surface conductivity at 200 degrees C was
especially influenced by P-O2, and the sensitivity of surface conductivity
to P-O2 increased with doping of La into CuO. The doping of La led to a cha
nge of chemisorbed oxygen species from O-2(-) to O-2(-) and resulted in an
increase in sensitivity to P-O2.