ALUMINUM-DOPED AND INDIUM-DOPED ZINC-OXIDE THIN-FILMS PREPARED BY DC MAGNETRON REACTIVE SPUTTERING

Electrically conductive, optically transparent aluminium- and indium-doped zinc oxide films have been produced by DC magnetron reactive sputtering of Zn-Al and Zn-In composite metal targets. The deposition parameters investigated include target design (zinc/dopant ratio), substrate temperature and the effect on film growth of ion-bombardment resulting from the use of an unbalanced DC magnetron. The process windows determined by the range of oxygen flows which produce films of low resistivity and high transparency were investigated for various target designs and deposition conditions. Ion bombardment of films deposited at low substrate temperatures leads to improved film transparency by partly re-sputtering unoxidised zinc. However, optimum quality films are produced only at those temperatures high enough to re-evaporate unoxidised zinc completely. Optimum indium-doped films of resistivity approximately 1.4 x 10(-3) OMEGA cm, were produced on substrates held at greater-than-or-equal-to 220-degrees-C. Aluminium-doped zinc oxide films were superior to indium-doped films in terms of both resistivity and transparency. Optimum aluminium-doped films of resistivity approximately 5 x 10(-4) OMEGA cm and luminous transmittance approximately 0.82 for a 750 nm thick film were produced on substrates held at greater-than-or-equal-to 180-degrees-C. Film composition, deposition rates and degradation in air and water are also discussed.