Thin, boron-doped diamond films formed on a silicon substrate were evaluated during water electrolysis in acidic solution in order to determine their potential for industrial use. Though the electrode exhibited overvoltages in excess of 2 V in the industrial current range, ozone gas was produced at a current efficiency of a few percent at ambient temperature. It was confirmed that the consumption rate of the highly doped sample was small and comparable with a platinumplated anode, indicating that the diamond is dimensionally stable under extreme conditions. The failure mechanism in the test is discussed on the basis of scanning electron microscopy, X-ray diffraction, and Raman analyses. The spalling of the film from the substrate, which was observed in the deteriorated sample after the electrolysis, is attributed to the residual stress that accumulated during the production process carried out under high temperature.

A model of the formation of a p-type surface conductive layer on deposited diamond films is proposed. According to the model, the ionization of acid in water produces oxonium ion ( H3O+) which reacts with hydrogen on diamond films and causes the creation of holes in diamond films. The model also explains the disappearance of the p-type surface conductive layer by the action of alkaline substances. The experimental results concerning the change in electrical resistance at the surface of diamond films can be explained using the proposed model.

A diamond field emitter array has been fabricated. by Chemical vapor deposition. Diamond was grown on an inverted pyramidal-shape Si substrate followed by removal of the substrate. The fabricated array was placed in a high vacuum pumping system with the pressure of ∼10−7 Torr and the emission current as a function of the anode voltage was measured. The distance between the tungsten anode and the diamond surface was held constant at 100 μm throughout the measurement. As a result, a current larger than 10−4 A was obtained for an anode voltage of 6 kV. A linear relationship in the Fowler–Nordheim plot indicated the existence of electron field emission from the fabricated diamond field emitter array.

The semiclassical approximation is extended to the case of ionisation of atoms by relativistic charged particles. The theory is formulated both for a relativistic and a non-relativistic electron description. For total cross sections the theory is shown to be equivalent to the relativistic plane-wave Born approximation. Numerical results for the impact parameter distribution of the ionisation probability for the K shell are given.

Characteristics of Schottky barriers formed on homoepitaxial diamond film have been studied. Current–voltage characteristics of Al contacts on both the as-grown film and the oxidized film show rectification. On the other hand, ohmic property is observed on Au/as-grown film while Au/oxidized film shows rectification. These results imply that the mechanism of the barrier formation on the as-grown diamond is drastically changed by oxidation. The difference of electrical properties between the as-grown film and the oxidized film is also observed from capacitance–voltage characteristics. This result suggests that additional acceptors which are not related to boron, exist in the as-grown film and disappear after oxidation.