Electrical properties of Al2O3 films for TFEL-devices made with sol–gel technology

Thin films of Al2O3 have been deposited on ITO-coated glass substrates by a sol–gel dipcoat process. Aluminium isopropoxide (Al(OC3H7)3) was used as the Al source material. X-ray diffraction measurements show that these films are amorphous. Scanning electron microscopy and atomic force microscopy images of the films have revealed a relatively flat surface with no cracks. The dielectric properties of these aluminium oxide thin films have been investigated in the frequency range of 15 Hz to 1 MHz. We have also compared the electrical behaviour of conventional double insulator thin-film electroluminescent devices where the bottom insulator was partly or fully replaced by a sol–gel layer. These devices behave largely normal but show signs of losses in the sol–gel layer, which are likely linked to its porosity. The interface between the sol–gel bottom insulator and the ZnS phosphor layer shows no severe premature charge transfer as is usual for a similar atomic layer deposition insulator.