| This dissertation describes an investigation of the growth and processing of aluminium oxide thin films. These oxide films, used as insulating barriers in magnetic and superconducting tunnel junctions, are typically formed by exposing an aluminium thin film to a controlled dose of pure oxygen at room temperature. The x-ray photoelectron spectroscopy results presented in this dissertation show that aluminium oxide layers grown using this method are oxygen deficient, and that their surfaces are covered with a layer of negatively-charged clusters of oxygen molecules weakly bonded to the positively-charged oxygen vacancies in the oxide.; The deposition of a metallic overlayer drives the chemisorbed oxygen into these oxide vacancies, provided that the work function of the overlayer metal is high enough to produce an electrochemical potential difference across the oxide. A low energy electron bombardment, in the range of 10--20 eV, can also be used to produce such a potential difference. The enhanced potential difference results in an increase in the oxide thickness as well as its oxygen content, pushing its stoichiometry closer to an ideal value of 1.5 (i.e., Al2O3).; Micron-sized aluminium oxide-based tunnel junctions which incorporate electron bombarded oxide layers show a significantly lower resistance noise figure at 4.2 K compared to tunnel junctions whose oxide layers were not electron bombarded. The decrease in the noise level is attributed to the filling of the oxygen vacancy sites in the oxide as a result of the electron bombardment, as the charge trapping behaviour of these vacancy sites is a major source of noise in tunnel junctions. |
