Parametric dependence of the properties of pulsed-laser-deposited diamond-like carbon films

The properties of Pulsed-Laser-Deposited Diamond-Like Carbon (PLD DLC) films are studied as functions of the power density Φ and the wavelength λ of the laser beam, and the incident angle θ of the beam relative to the normal of the target surface. All the films have a similar structure consisting of graphite particulates embedded in a continuous matrix, so the macroscopic performance of the films is determined by the overall contributions of the particulates and the matrix. The use of higher Φ, shorter λ, or larger θ leads to an enhancement of the diamond-like characteristics and a simultaneous increase of the particulate density. These two effects give opposite contributions to the electrical conductivity σR, leading to the following results. (i) σRdrops with increasing Φ in the low Φ range (region I) due to the stronger diamond-like nature of the matrix, but increases sharply after Φ has exceeded a threshold Φminas a result of the rapid increase in particulate density. (ii) In region I, the use of shorter λ or larger θ leads to a more diamond-like matrix, and this overwhelms the degradation effect caused by the slight increase in particulate density. The samples thus become more insulating. In the high Φ region (region II), however, the use of shorter λ or larger θ gives rise to higher particulate density, thereby increasing the electrical conductivity.