In Situ Localized Surface Plasmon Resonance (LSPR) Spectroscopy to Investigate Kinetics of Chemical Bath Deposition of CdS Thin Films

Techniques that can characterize the early stages of thin film deposition from liquid phase processes can aid greatly in our understanding of mechanistic aspects of chemical bath deposition (CBD). Here we have used localized surface plasmon resonance (LSPR) spectroscopy to monitor the in situ kinetics of early stage growth of cadmium sulfide (CdS) thin films on Ag nanoparticle on quartz substrates. Real-time shift during CdS deposition showed that the LSPR wavelength red-shifted rapidly due to random deposition of CdS on the substrate but saturated at longer times. LSPR modeling showed that these features could be interpreted as an initial deposition of CdS islands followed by preferential deposition onto itself. The CdS also showed significantly enhanced Raman signals up to 170 times due to surface-enhanced Raman scattering (SERS) from the CdS/Ag NP regions. The ex situ SERS effect supported the LSPR shift, suggesting that these techniques could be used to understand nucleation and growth phenomena from the liquid phase.