Electrical properties of Al 2 O 3 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.