Fluence Enhanced Optical Response of Ag Implanted Amorphous Carbon Thin Films

Abstract

Silver nanoparticles (NPs) are known to exhibit strong interaction with light photons because their surface conduction electrons undergo collective oscillations once photo-excited at specific wavelengths; the so-called surface plasmon resonance (SPR). Their incorporation into carbon-based material is shown to greatly influence the overall optical response of the matrix due to aggregation. In this paper, we studied the optical response of silver-irradiated amorphous carbon films due to varying fluence of 25 keV Ag ions in the range 2.5-3.4 × 10 16 ions/cm 2 . Raman spectroscopy provided an insight into the microstructural details of the Ag:a-C nanocomposites such that access to bond characteristics of the films is enabled by directly linking the Raman information with sp 2 /sp 3 configurations. Atomic force microscopy (AFM) analysis show significant increase in particle grain size and surface roughness of the films with increasing fluence while transmission electron microscopy (TEM) confirmed fluence-induced particle aggregation due to irradiation. Optical absorption studies revealed that the SPR of Ag NPs occurs in the wavelength range 418-395 nm in the irradiated films. The blue shift in plasmonic wavelength response is explained with respect to the fluence-induced increase in the particulate grain size and particle density as confirmed by AFM and TEM. The optical band gap energy (E g ) of the pristine carbon film decreased from 1.79 eV to 1.41 eV while Urbach parameter (E u ) increased from 0.01 eV to 12.0 eV, respectively with increasing fluence. These tunable optical parameters can be tailored into applications in surface coatings and as functional materials for solar cell efficiency enhancement.

Optical and Electronic Properties of Carbon-Based Nanomaterials and Composites

“…Going to ''extended" C systems, the role of amorphous hydrogenated carbon (a-C:H) in reinforcing the promising biodegradable polymer polyhydroxybutyrate (PHB), was discussed in [15]. It was shown that stable layers of a-C:H up to 450 nm can be deposited on PHB with customizable properties dependent on the thickness and growth plasma, and correlated to the sp 2 /sp 3 ratio within a-C:H. In addition, a study of Ag-bombarded amorphous carbon films (Ag:a-C) to obtain composites was reported in [16]. The work highlights that the Ag nanoparticle aggregation/size modifies the overall optical response of the nanocomposite causing a blue shift of the surface plasmon resonance wavelength and the tuning of the optical response of the material exploitable for optical coatings and solar applications.…”