Frequency dependence of the conductivity and dielectric constant of La2CuO4+y near the insulator-metal transition

Measurements are reported of the conductivity and dielectric constant at frequencies up to 10 MHz for a single crystal of La{sub 2}CuO{sub 4+{ital y}} with {ital y}{similar to}0.001 to 0.01. The reported behavior is typical of conventional doped semiconductors, with dielectric constant (at {ital y}=0) and effective mass that are not exceptionally large. The dielectric constant grows as the insulator-to-metal transition is approached, but only for the electric field in the CuO{sub 2} layers, indicating that the transition is two dimensional. The crossover to weak localization occurs close to the antiferromagnetic phase boundary.