Averaging of the electron effective mass in multicomponent transparent conducting oxides

We find that layered materials composed of various oxides of cations with s 2 electronic configuration, XY 2 O 4 , X = In or Sc, Y = Ga, Zn, Al, Cd and/or Mg, exhibit isotropic electron effective mass which can be obtained via averaging over those of the corresponding single-cation oxide constituents. This effect is due to a hybrid nature of the conduction band formed from the s -states of all cations and the oxygen p -states. Moreover, the observed insensitivity of the electron effective mass to the oxygen coordination and to the distortions in the cation-oxygen chains suggests that a similar behavior can be expected in the technologically important amorphous state. These findings significantly broaden the range of materials as efficient transparent conductor hosts.