Electronic structure and conductivity of nanocomposite metal (Au, Ag, Cu, Mo)-containing amorphous carbon films

Abstract

Abstract.In this work, we study the influence of the incorporation of different metals (Me = Au, Ag, Cu, Mo) on the electronic structure of amorphous carbon (a-C:Me) films. The films were produced at room temperature using a novel pulsed dual-cathode arc deposition technique.Compositional analysis was performed with secondary neutral mass spectroscopy whereas Xray diffraction was used to identify the formation of metal nanoclusters in the carbon matrix. The metal content incorporated in the nanocomposite films induces a drastic increase in the conductivity, in parallel with a decrease in the band gap corrected from Urbach energy. The electronic structure as a function of the Me content has been monitored by x-ray absorption near edge structure (XANES) at the C K-edge. XANES showed that the C host matrix has a dominant graphitic character and that it is not affected significantly by the incorporation of metal impurities, except for the case of Mo, where the modifications in the lineshape spectra indicated the formation of a carbide phase. Subtle modifications of the spectral lineshape are discussed in terms of nanocomposite formation.

Optical and elastic properties of diamond-like carbon with metallic inclusions: A theoretical study

“…For instance, the performance of a-C can be tuned with the incorporation of transition metal in the material, such as Ag, Cu, or Ti nanoparticles: 11,[13][14][15][16][17][18][19][20][21] for metal-containing DLC, the carbon matrix provides high mechanical strength and the metallic inclusion enhances optical absorption. The structure and properties of the composite generally depend on the preparation technique and the deposition conditions, 6,8 which make the identification of universal structure-property relationships a challenging task.…”

“…) and values in the range of 10 2 -10 16 X cm have been reported for the resistivity of DLC depending on preparation conditions. 9 Incorporation of metallic inclusions in a-C can increase the conductivity.…”

“…9 Incorporation of metallic inclusions in a-C can increase the conductivity. 9,16 As far as the electronic structure is concerned (see Fig. 3), the band tails are determined mainly from (valence) p and (conduction) pà states that arise from sp 2 -bonded C. 7,26,46 With increasing metal content (increasing content in sp 2 -bonded C), the pðÃÞ bands broaden and the band tails become wider.…”

Influence of Deposition Rate on Optical Properties of RF-Magnetron Sputtered Carbon–Nickel Composite Films Deposited at Different Deposition Times

“…By increasing the deposition time from 50 to 90 sec due to increasing RMS roughness, and hence decreasing absorption edge, the optical conductivity decreases. However, by increasing deposition time up to 180 sec because of increasing deposition rate, hence increasing density of localized states within gap, the optical conductivity increases, and at 600 sec, due to decreasing localized state, the optical conductivity decreases [17,28]. Figures 3(a) and (b) show the variation of (αhν) 2 and (αhν) 1/2 versus hv for films as a function of deposition time, respectively.…”

“…Furthermore, the change in refractive index is important for controlling optical properties of the films because optical properties are directly related to their structural and electronic properties [19]. An element such as Ni with low or without affinity to carbon atom leads to a relatively sharp interface between the carbon matrix and the metallic phase and therefore distinct properties are produced in comparison to carbide forming elements [20,21]. Moreover, nickel-carbon composite films are studied for their interesting properties such as residual stress reduction for hard films [22], improvement of the dielectric constant [23], or decrease of the friction coefficient [22] in conditions where constant deposition rates are synthesized.…”