EFFECT OF LASER POWER-DENSITY AND DEPOSITION TEMPERATURE ON ELECTRICAL AND OPTICAL-PROPERTIES OF PULSED-LASER ABLATED DIAMOND-LIKE CARBON-FILMS

Amorphous diamond-like carbon (DLC) thin films were deposited by pulse d laser ablation using an XeCl excimer laser and a pyrolytic graphite target. The effect of the laser power density and the substrate temper ature on the optical and electrical properties of the films was studie d. It was found to be possible to tailor the electrical and optical pr operties of the deposited films between diamond-like and graphite-like by varying the peak power density of the laser beam and the depositio n temperature. The optical band gap of the films varied from zero (dep osition temperature greater than or equal to 200 degrees C) to a maxim um value of 1.35 eV. The real part n of the visible wavelength refract ive index ranged from 2.4 to 2.5 for good quality DLC films. It was po ssible to vary the electrical conductivity by eight orders of magnitud e between DLC and graphite-like material. The conductivity of the DLC films exhibited an exp(-T--1/4) dependence on temperature that is char acteristic of hopping mechanisms; graphite-like films showed more band -type conductivity.