ELECTRON-TUNNELING INTO STRONGLY DISORDERED FILMS - THE INFLUENCE OF STRUCTURE ON ELECTRON-ELECTRON INTERACTIONS

We present measurements of the electronic tunneling density of states of ultrathin films with sheet resistances at 8 K in the range 100 OMEGA < R < 100 kOMEGA. We find that in the strongly disordered regime the Coulomb anomaly in the tunneling density of states grows in strength with R in a manner which depends strongly on film structure. These data demonstrate that the effective electron-electron interactions in disordered films depend on film structure in this regime. We discuss the implications of this behavior for the properties of superconductors near the two-dimensional superconductor-to-insulator transition.