Insights into the sputter-instigated valence plasmon oscillations in CIGSe thin films

Abstract

We report a unique methodology of triggering plasmonic excitations in sputtered ultrathin CIGSe films. In this approach of plasmonic excitation, secondary ion source present in the growth system instigates the formation of nanoclusters of its constituent elements, which is the source of plasmonic excitation. The formation of the nanoclusters during the growth is because of the distinct sputtering out rates of the various elements during the growth. For the verification of valence electron excitation and plasmonic oscillations, the studies performed as follows: a) investigation of electron energy loss from the ultraviolet-photoelectron spectroscopy measurements, b) quantification of the various electron energy loss contributions associated with the constituent element present in the films within the observed broad peaks in ultravoilet photoelectron spectroscopy (UPS) spectrum, c) estimation of particular plasmon contribution, i.e., particle, valence-surface, and valence-bulk plasmon at the air/thin-film interface, and within the thin film, d) verification of plasmonic behavior by analyzing different optical properties performing spectroscopic ellipsometry measurements, 5) validation of the nanocluster emergence in ultrathin CIGSe thin films deploying Field Emission Scanning Electron Microscopy. This approach is promising in terms of improving the solar cell performance parameters by supplementing the optical path length within the absorber in the broad spectral range without the need of externally supplied metal nanoparticles.