A method has been developed for evaluating the wear durability and adhesion characteristics of ultrathin overcoat films. The relationship between the wear depth and applied load or between the wear depth and number of scanning-scratch cycles is used in AFM nanowear tests. Inherent wear durability, which is independent of adhesion or substrate hardness, can be evaluated from the relationship between wear depth and applied load at relatively low loads, and the adhesion characteristics can be evaluated from the relationship at relatively high loads. Wear durability can be evaluated with a small number of scanning-scratch cycles and adhesion with a large number of cycles.

To achieve conductive and wear-durable carbon thin films by metal doping, we deposited Au-, Pt-, and Pd-doped carbon thin films by RF sputtering, and evaluated the dopant concentrations, resistivity, and scratch hardness. Among the doped films, the Pt-doped film with low Pt concentration was most suitable from a practical perspective.

To realize highly conductive and wear-durable thin films, we deposited metal doped carbon films onto silicon substrates by RF sputtering method. The dopant metals were various precious metals and transition metals. The electrical conductivity and wear durability of the deposited films were evaluated. We have found that Ir doping especially increased the electrical conductivity for the given amount of dopant metal. The wear durability of Ir-doped carbon films did not deteriorate even below a 7 at.% Ir concentration, and the conductivity of 7 at.% Ir-doped carbon was twenty times that of a non-doped carbon thin film.

Miniaturized sealed contacts can be made highly reliable by controlling the atmosphere. This paper studies the effects of oxygen concentration on adhesion and contact resistance characteristics as well as those of oxygen dissipation for silver-palladium alloy and gold-palladium alloy contact. There is a permissible oxygen concentration range where adhesion is prevented and contact resistance is also stable. This range depends on the corrosive resistance of the contact materials. Oxygen concentration varies not only due to air leakage, but also due to oxygen dissipation caused by the oxidation of contact metals in sealed contact enclosures. If the most suitable contact materials and oxygen concentration are selected, the oxygen concentration range can be wide enough to allow changes in oxygen concentration within the enclosures. Switches where silver-palladium alloy mating with gold-palladium alloy contacts are sealed in a nitrogen atmosphere containing about 5% oxygen are confirmed to have characteristics that satisfy the conditions required for practical speech path equipment. This confirms that atmosphere control is a practical way to produce highly reliable sealed contacts.