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

Abstract

The properties of Pulsed-Laser-Deposited Diamond-Like Carbon (PLD DLC) films are studied as functions of the power densityΦ and the wavelengthλ of the laser beam, and the incident angleϑ 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 higherΦ, shorterλ, or largerϑ 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 conductivityσ _R, leading to the following results. (i) σ_R drops with increasingΦ in the lowΦ range (region I) due to the stronger diamond-like nature of the matrix, but increases sharply afterΦ has exceeded a thresholdΦ _min as a result of the rapid increase in particulate density. (ii) In region I, the use of shorterλ or largerϑ 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 highΦ region (region II), however, the use of shorterλ or largerϑ gives rise to higher particulate density, thereby increasing the electrical conductivity.