Dominating Coulomb-interaction effects in amorphousInxOyfilms

Insulating thin three-dimensional (3D) amorphous films of ${\mathrm{In}}_{\mathrm{x}}$ ${\mathrm{O}}_{\mathrm{y}}$ exhibit the surprising resistance-versus-temperature dependence R∝exp[($T_0$/T${)}^{1/2}$] between 6 and 106 K. The (1/T${)}^{1/2}$ exponent in the resistance expression, the observed positive magnetoresistance behavior, and the lack of dependence of the magnetoresistance upon magnetic field orientation all suggest a dominating Coulomb electron-electron interaction transport mechanism. Interestingly, the experimental magnetoconductance data could be well described using the 3D electron-electron spin-splitting interaction theory derived for metallic systems, but modified by a simple temperature prescaling factor, 1/exp[($T_0$/T${)}^{1/2}$]. This prescaling factor accounts for the strong temperature dependence of the conductivity that is present in insulating films.