Deposition and characterization of multilayer DLC:Mo thin films grown on silicon substrate by off-axis pulsed laser deposition technique

Abstract

Off-axis pulsed laser deposition technique was used to deposit a diamond-like carbon (DLC) thin film and three multilayer DLC:Mo thin films of various compositions on p-type Si (111) substrate at room temperature keeping the DLC content constant. Excimer laser was used to ablate graphite and Mo targets in a vacuum of ∼10−5mbar, whereas the p-type Si (111) substrate was placed downside the target at a distance of 1cm in off-axis PLD geometry. Morphological, structural, optical, and electrical characteristics of the deposited thin films were then investigated. SEM images of the thin films show that surface roughness increases as Mo content in the film increases. XRD patterns of DLC:Mo thin films rule out any carbide formation. Both crystallite size of Mo particles and film thickness increase whereas microstrain decreases with the increase in Mo content. Moreover, both refractive index and indirect optical band gap decrease exponentially while Urbach energy increases linearly with the increase in Mo content. Electrical resistivity of the thin films has been found to follow an exponential decay with the increase in Mo content in multilayer DLC:Mo thin films.